Phylogenetic Variation in the Silicon Composition of Plants

Abstract

• Background and Aims Silicon (Si) in plants provides structural support and improves tolerance to diseases, drought and metal toxicity. Shoot Si concentrations are generally considered to be greater in monocotyledonous than in non-monocot plant species. The phylogenetic variation in the shoot Si concentration of plants reported in the primary literature has been quantified.

• Methods Studies were identified which reported Si concentrations in leaf or non-woody shoot tissues from at least two plant species growing in the same environment. Each study contained at least one species in common with another study.

• Key Results Meta-analysis of the data revealed that, in general, ferns, gymnosperms and angiosperms accumulated less Si in their shoots than non-vascular plant species and horsetails. Within angiosperms and ferns, differences in shoot Si concentration between species grouped by their higher-level phylogenetic position were identified. Within the angiosperms, species from the commelinoid monocot orders Poales and Arecales accumulated substantially more Si in their shoots than species from other monocot clades.

• Conclusions A high shoot Si concentration is not a general feature of monocot species. Information on the phylogenetic variation in shoot Si concentration may provide useful palaeoecological and archaeological information, and inform studies of the biogeochemical cycling of Si and those of the molecular genetics of Si uptake and transport in plants.

INTRODUCTION

Silicon is the second most abundant element in the soil after oxygen (reviewed by Epstein, 1999; Richmond and Sussman, 2003). Most Si is present in the soil as insoluble oxides or silicates, although soluble silicic acid occurs in the range of 0·1–0·6 mm. Silicon is also one of the most abundant mineral elements in plant tissues and shoot concentrations in excess of 10 % d. wt have been reported (Epstein, 1999). Plants growing under natural conditions do not appear to suffer from Si deficiencies. However, Si-containing fertilizers are routinely applied to several crops including rice (Pereira et al., 2004) and sugar cane (Savant et al., 1999) to increase crop yield and quality. Increased Si supply improves the structural integrity of crops and may also improve plant tolerance to diseases, drought and metal toxicities (reviewed by Epstein, 1999; Richmond and Sussman, 2003; Ma, 2004). For example, Si deposition in the cell walls of root endodermal cells may contribute to the maintenance of an effective apoplastic barrier and thereby improve plant resistance to disease and drought stresses (Lux et al., 2002, 2003a, b; Hattori et al., 2005), whilst intra- and extracellular deposition of aluminosilicates in roots and shoots is thought to protect some species from potential Al toxicity (Hodson and Evans, 1995; Hodson and Sangster, 1999; Britez et al., 2002; Jansen et al., 2003; Wang et al., 2004).

Early studies of Si in plants noted that species of Poaceae contained between 10 and 20 times the concentration of Si found in non-monocotyledonous species (de Saussure, 1804; Jones and Handreck, 1967). Recent reviews report that Si accumulation is, in general, higher in monocot than in non-monocot species (Epstein, 1999; Richmond and Sussman, 2003). However, detailed sampling of specimens from botanical gardens by Takahashi and colleagues (reviewed in Ma and Takahashi, 2002, and references therein) indicates that Si accumulation is largely restricted to primitive land plants and to certain monocot clades, namely the Poaceae, Cyperaceae and Commelinaceae. There is also evidence from these detailed studies that Si may accumulate in certain dicot clades such as the Urticaceae and Cucurbitaceae. In this study, the phylogenetic variation in shoot Si concentration amongst plant species has been quantified by analysing all of the appropriate literature data that could be sourced. These include the extensive data compiled by Takahashi and colleagues (Ma and Takahashi, 2002, and references therein). Using a recent consensus angiosperm phylogeny, it was thus possible to test the hypothesis that high shoot Si concentration is a general feature of monocot species, and it was also possible to identify Si accumulation features in several other well-represented clades of plant species.

MATERIALS AND METHODS

Data from 125 studies, contained in 54 papers in the primary literature, were identified that reported Si concentrations of leaf or non-woody shoot tissues in at least two species growing in the same environment, and which contained at least one species in common with another study (studies listed in the Appendix; additional information is available online at http://aob.oxfordjournals.org). Wherever possible, species nomenclature was based on the original study. Where taxonomic uncertainties occurred, the closest species match was inferred. Angiosperm species nomenclature and familial assignment/informal groupings were based on the United States Department of Agriculture (USDA) National Genetic Resources Program. Germplasm Resources Information Network (GRIN) (http://www.ars-grin.gov/cgi-bin/npgs/html/index.pl) and the Angiosperm Phylogeny Group classification (APG, 1998). Non-angiosperm species nomenclature and family assignment was based on information obtained from (a) The Flowering Plant Gateway (http://www.csdl.tamu.edu/FLORA/newgate/gateopen.htm); (b) The International Plant Names Index (http://www.ipni.org/index.html); or (c) The National Center for Biotechnology Information (NCBI; http://www.ncbi.nlm.nih.gov).

The mean relative shoot Si concentration of each species across all studies was estimated. To adjust for differences in shoot Si concentration between studies, a residual maximum likelihood (REML) procedure was used. All methods have been described previously (Broadley et al., 2003). Briefly, the REML procedure adjusts for differences in between-study variances and means in order to generate an overall treatment mean, which in this case is the shoot Si concentration for each species, i.e. species means are effectively averaged across studies. Since the REML fitting procedures can produce negative treatment means, species Si concentrations were considered as relative values on a linear scale. Estimates of variation in shoot Si concentration were simultaneously fit to a variance components model of [study+(group/order/family/genus/species)]. To test for significant differences between species classified by their higher-level phylogenetic position, one-way ANOVA was performed on restricted subsets of the data. All statistical analyses were performed using GenStat (Release 6.1.0.200, VSN International, Oxford, UK).

RESULTS AND DISCUSSION

Seven hundred and thirty-five species were sampled from 125 studies (Table 1; additional information is available online at http://aob.oxfordjournals.org), including 600 species of angiosperms, 67 gymnosperms, 59 ferns (Polypodiophyta), five clubmosses (Lycopodiophyta), two horsetails (Equisetophyta), one liverwort (Marchantiophyta) and one moss (Bryophyta). Within a variance components model of [study+(group/order/family/genus/species)], group and order accounted for 67 % of the variation in relative shoot Si concentration (Table 2). The remaining variation was attributed to within-order (17 %) and to between-study (16 %) variance components. Thus, high-level phylogenetic position influences the shoot Si concentration of plants. This observation is consistent with literature and experimental studies of other elements including Ca, K, Mg (Broadley et al., 2003, 2004; White and Broadley, 2003; White, 2005), Ni and Zn (Broadley et al., 2001). In contrast, variation in the relative shoot concentrations of N, P (Broadley et al., 2004) and Se (White et al., 2004) is dominated by species-level variance components, and thus there is no evidence that the tissue concentration of these elements differs systematically between groups of species according to their phylogenetic position.

Table 1.

Mean relative shoot Si concentration of 735 plant species. Data are from 125 studies, contained in 54 papers in the primary literature, in which Si concentrations of leaf or non-woody shoot tissue were reported. Each study included at least two plant species growing in the same environment, and each study contained at least one species in common with another study. A residual maximum likelihood procedure was performed on the 1066 linked data to estimate the mean relative shoot Si concentration of species, adjusted for differences between studies.

Group	Order	Family	Species	Mean relative shoot Si concentration	Ranking	Study number (full reference in Appendix)
Angiosperm	Acorales	Acoraceae	Acorus calamus	−0·058	57	83
Angiosperm	Acorales	Acoraceae	Acorus gramineus	0·002	91	83
Angiosperm	Alismatales	Alismataceae	Sagittaria lancifolia	0·442	337	74
Angiosperm	Alismatales	Alismataceae	Sagittaria trifolia	0·292	260	83
Angiosperm	Alismatales	Araceae	Amorphophallus rivieri	−0·058	58	83
Angiosperm	Alismatales	Araceae	Pistia stratiotes	0·072	145	83
Angiosperm	Alismatales	Araceae	Zamioculcas zamiifolia	0·528	365	71
Angiosperm	Alismatales	Cymodoceaceae	Halodule beaudettei	0·999	530	79
Angiosperm	Alismatales	Juncaginaceae	Triglochin maritima	0·565	378	20, 106
Angiosperm	Alismatales	Juncaginaceae	Triglochin striata	1·033	540	78
Angiosperm	Alismatales	Ruppiaceae	Ruppia maritima	1·779	653	79
Angiosperm	Apiales	Apiaceae	Ammi visnaga	0·729	462	19
Angiosperm	Apiales	Apiaceae	Conium maculatum	−0·068	54	83
Angiosperm	Apiales	Apiaceae	Ferula varia	1·069	556	69
Angiosperm	Apiales	Apiaceae	Foeniculum vulgare	0·623	403	19
Angiosperm	Apiales	Apiaceae	Lilaeopsis chinensis	2·242	682	74
Angiosperm	Apiales	Araliaceae	Aralia cordata	−0·018	75	83
Angiosperm	Apiales	Araliaceae	Hydrocotyle bonariensis	0·513	364	78
Angiosperm	Apiales	Araliaceae	Panax ginseng	0·102	161	83
Angiosperm	Apiales	Araliaceae	Polyscias filicifolia	0·358	294	71
Angiosperm	Apiales	Pittosporaceae	Pittosporum tobira	0·042	115	86
Angiosperm	Aquifoliales	Aquifoliaceae	Ilex aquifolium	0·002	92	83
Angiosperm	Aquifoliales	Aquifoliaceae	Ilex integra	0·182	204	86
Angiosperm	Aquifoliales	Aquifoliaceae	Ilex latifolia	0·122	173	86
Angiosperm	Arecales	Arecaceae	Phoenix dactylifera	0·172	197	83
Angiosperm	Arecales	Arecaceae	Phoenix roebelenii	0·202	219	83
Angiosperm	Arecales	Arecaceae	Rhapis humilis	0·422	329	83
Angiosperm	Arecales	Arecaceae	Trachycarpus fortunei	1·312	597	83
Angiosperm	Arecales	Arecaceae	Washingtonia filifera	1·738	650	71
Angiosperm	Arecales	Arecaceae	Caryota mitis	1·598	636	71
Angiosperm	Arecales	Arecaceae	Sabal etonia	1·910	663	66
Angiosperm	Arecales	Arecaceae	Sabal minor	1·036	543	76
Angiosperm	Arecales	Arecaceae	Serenoa repens	2·443	691	66, 79
Angiosperm	Asparagales	Agavaceae	Agave americana	0·042	116	83
Angiosperm	Asparagales	Agavaceae	Hosta longissima	−0·008	82	83
Angiosperm	Asparagales	Agavaceae	Yucca aloifolia	0·056	127	76
Angiosperm	Asparagales	Agavaceae	Yucca filamentosa	−0·018	76	83
Angiosperm	Asparagales	Alliaceae	Allium fistulosum	0·072	146	83
Angiosperm	Asparagales	Amaryllidaceae	Crinum asiaticum	−0·078	49	83
Angiosperm	Asparagales	Amaryllidaceae	Lycoris radiata	−0·088	47	83
Angiosperm	Asparagales	Amaryllidaceae	Zephyranthes candida	0·002	93	83
Angiosperm	Asparagales	Anemarrhenaceae	Anemarrhena asphodeloides	−0·018	77	83
Angiosperm	Asparagales	Asparagaceae	Asparagus cochinchinensis	0·152	191	83
Angiosperm	Asparagales	Asparagaceae	Asparagus officinalis	0·341	281	69, 83
Angiosperm	Asparagales	Asphodelaceae	Aloë arborescens	0·062	132	83
Angiosperm	Asparagales	Convallariaceae	Aspidistra elatior	−0·038	65	83
Angiosperm	Asparagales	Convallariaceae	Convallaria majalis	0·432	333	83
Angiosperm	Asparagales	Convallariaceae	Polygonatum odoratum	−0·008	83	83
Angiosperm	Asparagales	Convallariaceae	Rohdea japonica	0·152	192	83
Angiosperm	Asparagales	Convallariaceae	Sansevieria trifasciata	−0·088	48	83
Angiosperm	Asparagales	Convallariaceae	Smilacina japonica	0·442	338	83
Angiosperm	Asparagales	Hemerocallidaceae	Hemerocallis fulva	0·082	148	83
Angiosperm	Asparagales	Iridaceae	Iris ensata	0·052	123	83
Angiosperm	Asparagales	Iridaceae	Iris florentina	−0·018	78	83
Angiosperm	Asparagales	Iridaceae	Iris setosa	0·082	149	83
Angiosperm	Asparagales	Orchidaceae	Bletilla striata	0·372	301	83
Angiosperm	Asparagales	Orchidaceae	Spiranthes sinensis	−0·038	66	83
Angiosperm	Asterales	Asteraceae	Achillea millefolium	1·438	613	36
Angiosperm	Asterales	Asteraceae	Anaphalis margaritacea	−0·192	43	36
Angiosperm	Asterales	Asteraceae	Artemisia absinthium	0·222	227	83
Angiosperm	Asterales	Asteraceae	Artemisia cana	0·263	250	7
Angiosperm	Asterales	Asteraceae	Artemisia frigida	0·573	380	7
Angiosperm	Asterales	Asteraceae	Artemisia gnaphalodes	0·120	171	6
Angiosperm	Asterales	Asteraceae	Artemisia maritima	0·002	94	83
Angiosperm	Asterales	Asteraceae	Artemisia tridentata	0·665	431	12, 13
Angiosperm	Asterales	Asteraceae	Aster laevis	0·260	243	6
Angiosperm	Asterales	Asteraceae	Aster macrophyllus	0·698	446	36
Angiosperm	Asterales	Asteraceae	Aster tenuifolia	0·030	108	75, 77
Angiosperm	Asterales	Asteraceae	Aster tripolium	0·457	346	20
Angiosperm	Asterales	Asteraceae	Baccharis halimifolia	0·032	109	83
Angiosperm	Asterales	Asteraceae	Baccharis trimera	0·362	296	88
Angiosperm	Asterales	Asteraceae	Boltonia asteroides	1·242	585	74
Angiosperm	Asterales	Asteraceae	Borrichia frutescens	0·556	376	78, 79
Angiosperm	Asterales	Asteraceae	Centaurea iberica	0·709	451	19
Angiosperm	Asterales	Asteraceae	Chamomilla recutita	0·062	133	83
Angiosperm	Asterales	Asteraceae	Chrysanthemum coronarium	0·082	150	83
Angiosperm	Asterales	Asteraceae	Chrysanthemum morii	0·243	236	90
Angiosperm	Asterales	Asteraceae	Conyza canadensis	0·635	412	19
Angiosperm	Asterales	Asteraceae	Eclipta erecta	0·771	472	19
Angiosperm	Asterales	Asteraceae	Erigeron crispus	0·608	392	19
Angiosperm	Asterales	Asteraceae	Eupatorium fortunei	0·272	253	83
Angiosperm	Asterales	Asteraceae	Grindelia squarrosa	0·717	458	82
Angiosperm	Asterales	Asteraceae	Helianthus angustifolius	1·127	568	82
Angiosperm	Asterales	Asteraceae	Helianthus annuus	1·876	661	107, 108
Angiosperm	Asterales	Asteraceae	Helianthus atrorubens	1·047	547	82
Angiosperm	Asterales	Asteraceae	Helianthus maximilianii	2·607	696	8
Angiosperm	Asterales	Asteraceae	Helianthus tuberosus	2·747	704	82
Angiosperm	Asterales	Asteraceae	Inula graveolens	0·773	473	19
Angiosperm	Asterales	Asteraceae	Inula helenium	0·769	471	69
Angiosperm	Asterales	Asteraceae	Inula viscosa	0·678	432	19
Angiosperm	Asterales	Asteraceae	Iva frutescens	0·906	508	76
Angiosperm	Asterales	Asteraceae	Lactuca serriola	0·792	478	19
Angiosperm	Asterales	Asteraceae	Leontodon hispidus	0·230	231	18
Angiosperm	Asterales	Asteraceae	Megalodonta tripartita	0·724	459	19
Angiosperm	Asterales	Asteraceae	Picris echioides	0·709	450	19
Angiosperm	Asterales	Asteraceae	Pluchea purpurascens	0·392	308	75
Angiosperm	Asterales	Asteraceae	Polymnia uvedalia	0·499	361	76, 81
Angiosperm	Asterales	Asteraceae	Pulicaria dysenterica	0·618	397	19
Angiosperm	Asterales	Asteraceae	Senecio fuchsii	0·530	368	37, 42, 44, 45
Angiosperm	Asterales	Asteraceae	Seriphidium maritimum	0·657	427	20
Angiosperm	Asterales	Asteraceae	Solidago sempervirens	0·412	323	74
Angiosperm	Asterales	Asteraceae	Sonchus oleraceus	0·689	440	19
Angiosperm	Asterales	Asteraceae	Trilisa odoratissima	0·639	415	79
Angiosperm	Asterales	Asteraceae	Xanthium strumarium	0·708	449	19
Angiosperm	Asterales	Lobeliaceae	Lobelia cardinalis	0·222	225	75
Angiosperm	Brassicales	Bataceae	Batis maritima	0·409	321	79
Angiosperm	Brassicales	Brassicaceae	Armoracia rusticana	−0·058	59	83
Angiosperm	Brassicales	Brassicaceae	Brassica alba	0·226	230	65
Angiosperm	Brassicales	Brassicaceae	Brassica napus	−0·116	45	5, 93
Angiosperm	Brassicales	Brassicaceae	Brassica rapa	−1·902	13	93, 94, 95, 96
Angiosperm	Brassicales	Brassicaceae	Hirschfeldia incana	0·740	464	19
Angiosperm	Brassicales	Brassicaceae	Nasturtium officinale	0·830	487	70
Angiosperm	Brassicales	Brassicaceae	Wasabia japonica	0·042	117	83
Angiosperm	Brassicales	Tropaeolaceae	Tropaeolum majus	−0·078	50	83
Angiosperm	Caryophyllales	Amaranthaceae	Alternanthera sessilis	0·837	492	19
Angiosperm	Caryophyllales	Amaranthaceae	Amaranthus albus	0·625	404	19
Angiosperm	Caryophyllales	Amaranthaceae	Amaranthus gracilis	0·619	399	19
Angiosperm	Caryophyllales	Amaranthaceae	Amaranthus graecizans	0·600	388	19
Angiosperm	Caryophyllales	Amaranthaceae	Amaranthus retroflexus	0·758	469	19
Angiosperm	Caryophyllales	Amaranthaceae	Amaranthus spp.	2·607	697	8
Angiosperm	Caryophyllales	Amaranthaceae	Amaranthus viridis	0·052	124	83
Angiosperm	Caryophyllales	Amaranthaceae	Atriplex canescens	0·357	293	8
Angiosperm	Caryophyllales	Amaranthaceae	Atriplex littoralis	0·347	283	20
Angiosperm	Caryophyllales	Amaranthaceae	Atriplex nuttallii	0·393	311	7
Angiosperm	Caryophyllales	Amaranthaceae	Atriplex portulacoides	0·497	360	20
Angiosperm	Caryophyllales	Amaranthaceae	Atriplex prostrata	0·347	284	20
Angiosperm	Caryophyllales	Amaranthaceae	Atriplex rosea	0·695	443	19
Angiosperm	Caryophyllales	Amaranthaceae	Chenopodium album	0·421	328	19, 75
Angiosperm	Caryophyllales	Amaranthaceae	Chenopodium murale	0·724	460	19
Angiosperm	Caryophyllales	Amaranthaceae	Chenopodium opulifolium	0·665	430	19
Angiosperm	Caryophyllales	Amaranthaceae	Eurotia lanata	0·393	312	7
Angiosperm	Caryophyllales	Amaranthaceae	Kochia scoparia	0·967	523	8
Angiosperm	Caryophyllales	Amaranthaceae	Salicornia bigelovii	0·629	408	79
Angiosperm	Caryophyllales	Amaranthaceae	Salicornia europaea	0·347	282	20
Angiosperm	Caryophyllales	Amaranthaceae	Salicornia virginica	0·289	257	79
Angiosperm	Caryophyllales	Amaranthaceae	Salsola kali	1·017	535	8
Angiosperm	Caryophyllales	Amaranthaceae	Suaeda maritima	0·467	351	20
Angiosperm	Caryophyllales	Caryophyllaceae	Dianthus superbus	−0·038	67	83
Angiosperm	Caryophyllales	Caryophyllaceae	Saponaria officinalis	0·172	198	83
Angiosperm	Caryophyllales	Caryophyllaceae	Spergularia media	0·347	285	20
Angiosperm	Caryophyllales	Molluginaceae	Glinus lotoides	0·631	409	19
Angiosperm	Caryophyllales	Plumbaginaceae	Limonium carolinianum	0·247	238	73
Angiosperm	Caryophyllales	Plumbaginaceae	Limonium vulgare	0·347	286	20
Angiosperm	Caryophyllales	Polygonaceae	Polygonum acuminatum	0·740	465	19
Angiosperm	Caryophyllales	Polygonaceae	Polygonum arenastrum	0·614	394	19
Angiosperm	Caryophyllales	Polygonaceae	Polygonum aviculare	1·709	646	69
Angiosperm	Caryophyllales	Polygonaceae	Polygonum fagopyrum	−0·021	74	5
Angiosperm	Caryophyllales	Polygonaceae	Polygonum hydropiper	0·052	125	83
Angiosperm	Caryophyllales	Polygonaceae	Polygonum lapathifolium	0·653	424	19
Angiosperm	Caryophyllales	Polygonaceae	Polygonum patulum	0·615	395	19
Angiosperm	Caryophyllales	Polygonaceae	Polygonum punctatum	1·279	590	79
Angiosperm	Caryophyllales	Polygonaceae	Polygonum salicifolium	0·605	390	19
Angiosperm	Caryophyllales	Polygonaceae	Polygonum senegalense	0·620	400	19
Angiosperm	Caryophyllales	Polygonaceae	Rumex dentatus	0·607	391	19
Angiosperm	Caryophyllales	Tamaricaceae	Tamarix chinensis	0·442	339	83
Angiosperm	Caryophyllales	Tamaricaceae	Tamarix jordanis	0·645	418	19
Angiosperm	Commelinales	Commelinaceae	Tradescantia ohiensis	0·292	261	83
Angiosperm	Cornales	Cornaceae	Alangium platanifolium	0·152	188	86
Angiosperm	Cornales	Cornaceae	Cornus stolonifera	0·350	290	26
Angiosperm	Cornales	Hydrangeaceae	Hydrangea macrophylla	0·332	278	83, 86
Angiosperm	Cornales	Hydrangeaceae	Philadelphus satsumi	−0·048	60	83
Angiosperm	Cucurbitales	Cucurbitaceae	Benincasa hispida	0·322	271	83
Angiosperm	Cucurbitales	Cucurbitaceae	Citrullus lanatus	0·837	493	103
Angiosperm	Cucurbitales	Cucurbitaceae	Ecballium elaterium	0·472	353	83
Angiosperm	Cucurbitales	Cucurbitaceae	Luffa acutangula	0·422	330	83
Angiosperm	Dipsacales	Caprifoliaceae	Symphoricarpos occidentalis	0·540	371	6
Angiosperm	Dipsacales	Valerianaceae	Valeriana officinalis	0·709	452	69
Angiosperm	Ericales	Clethraceae	Clethra alnifolia	1·199	581	79
Angiosperm	Ericales	Cyrillaceae	Cliftonia monophylla	0·419	327	79
Angiosperm	Ericales	Ericaceae	Arctostaphylos uva-ursi	0·322	273	15
Angiosperm	Ericales	Ericaceae	Calluna vulgaris	0·729	463	3, 15, 37
Angiosperm	Ericales	Ericaceae	Ceratiola ericoides	0·309	265	79
Angiosperm	Ericales	Ericaceae	Empetrum nigrum	0·392	310	15
Angiosperm	Ericales	Ericaceae	Erica canaliculata	0·062	134	83
Angiosperm	Ericales	Ericaceae	Loiseleuria procumbens	0·453	343	15
Angiosperm	Ericales	Ericaceae	Lyonia ferruginea	0·578	381	66
Angiosperm	Ericales	Ericaceae	Pieris japonica	0·062	131	86
Angiosperm	Ericales	Ericaceae	Rhododendron ferrugineum	0·322	274	15
Angiosperm	Ericales	Ericaceae	Rhododendron japonicum	0·322	272	83
Angiosperm	Ericales	Ericaceae	Rhododendron pulchrum	0·152	189	86
Angiosperm	Ericales	Ericaceae	Vaccinium myrtillus	0·082	147	3, 15, 40, 43, 44, 46, 49, 50
Angiosperm	Ericales	Ericaceae	Vaccinium uliginosum	0·350	288	15
Angiosperm	Ericales	Ericaceae	Vaccinium vitis-idaea	0·322	275	15
Angiosperm	Ericales	Polemoniaceae	Phlox subulata	1·012	532	83
Angiosperm	Ericales	Primulaceae	Glaux maritima	1·063	551	106
Angiosperm	Ericales	Primulaceae	Primula veris	0·709	453	69
Angiosperm	Ericales	Styracaceae	Styrax japonicus	0·132	179	86
Angiosperm	Ericales	Ternstroemiaceae	Cleyera ochnacea	0·102	160	86
Angiosperm	Ericales	Ternstroemiaceae	Ternstroemia japonica	0·122	174	86
Angiosperm	Ericales	Theaceae	Camellia japonica	0·022	105	83, 86
Angiosperm	Ericales	Theaceae	Camellia sasanqua	0·117	168	83, 86
Angiosperm	Ericales	Theaceae	Eurya japonica	0·122	175	86
Angiosperm	Ericales	Theaceae	Thea sinensis	−0·025	72	23, 83
Angiosperm	Fabales	Fabaceae	Albizia julibrissin	0·002	95	83
Angiosperm	Fabales	Fabaceae	Alhagi mannifera	0·638	414	19
Angiosperm	Fabales	Fabaceae	Cajanus cajan	1·577	633	8
Angiosperm	Fabales	Fabaceae	Cercis canadensis	0·350	291	26
Angiosperm	Fabales	Fabaceae	Desmodium uncinatum	−0·433	35	85
Angiosperm	Fabales	Fabaceae	Galega orientalis	0·108	164	87, 92
Angiosperm	Fabales	Fabaceae	Gleditsia triacanthos	0·262	249	26
Angiosperm	Fabales	Fabaceae	Glycine max	1·399	610	21, 22, 107, 108
Angiosperm	Fabales	Fabaceae	Glycine wightii	−0·483	34	85
Angiosperm	Fabales	Fabaceae	Gymnocladus dioicus	0·360	295	26
Angiosperm	Fabales	Fabaceae	Hedysarum americanum	0·250	239	6
Angiosperm	Fabales	Fabaceae	Lathyrus ochroleucus	0·410	322	6
Angiosperm	Fabales	Fabaceae	Lotus corniculatus	−0·076	53	18, 36
Angiosperm	Fabales	Fabaceae	Lupinus argenteus	0·450	341	6
Angiosperm	Fabales	Fabaceae	Lupinus nanus	0·277	256	30, 32
Angiosperm	Fabales	Fabaceae	Medicago sativa	−0·228	42	5, 85, 93
Angiosperm	Fabales	Fabaceae	Melilotus albus	0·704	447	19
Angiosperm	Fabales	Fabaceae	Phaseolus atropurpureus	−0·433	36	85
Angiosperm	Fabales	Fabaceae	Phaseolus vulgaris	0·949	519	123, 124
Angiosperm	Fabales	Fabaceae	Pisum sativum	0·276	254	65
Angiosperm	Fabales	Fabaceae	Sophora flavescens	−0·048	61	83
Angiosperm	Fabales	Fabaceae	Sophora japonica	−0·028	68	83
Angiosperm	Fabales	Fabaceae	Trifolium fragiferum	0·626	405	19
Angiosperm	Fabales	Fabaceae	Trifolium hybridum	−0·152	44	36
Angiosperm	Fabales	Fabaceae	Trifolium incarnatum	0·216	223	65
Angiosperm	Fabales	Fabaceae	Trifolium pratense	−0·028	71	30, 31, 32, 36, 85, 93
Angiosperm	Fabales	Fabaceae	Trifolium repens	−0·023	73	36, 90
Angiosperm	Fabales	Fabaceae	Trifolium subterraneum	0·877	500	85
Angiosperm	Fabales	Fabaceae	Vicia americana	0·240	234	6
Angiosperm	Fabales	Fabaceae	Vicia villosa	−0·043	64	23
Angiosperm	Fabales	Fabaceae	Wisteria brachybotrys	0·142	182	83
Angiosperm	Fagales	Betulaceae	Alnus viridis	0·364	297	15
Angiosperm	Fagales	Betulaceae	Betula pendula	0·659	428	4
Angiosperm	Fagales	Betulaceae	Carpinus caroliniana	0·547	373	26
Angiosperm	Fagales	Betulaceae	Ostrya virginiana	0·402	317	26
Angiosperm	Fagales	Fagaceae	Fagus sylvatica	6·089	732	2, 3, 28
Angiosperm	Fagales	Fagaceae	Quercus alba	0·678	434	26
Angiosperm	Fagales	Fagaceae	Quercus chapmanii	0·620	401	66
Angiosperm	Fagales	Fagaceae	Quercus geminata	1·064	554	66
Angiosperm	Fagales	Fagaceae	Quercus imbricaria	0·435	335	26
Angiosperm	Fagales	Fagaceae	Quercus laevis	0·061	130	67
Angiosperm	Fagales	Fagaceae	Quercus macrocarpa	0·463	349	26
Angiosperm	Fagales	Fagaceae	Quercus muehlenbergii	0·528	366	26
Angiosperm	Fagales	Fagaceae	Quercus myrtifolia	0·648	419	66
Angiosperm	Fagales	Fagaceae	Quercus petraea	1·962	668	28
Angiosperm	Fagales	Fagaceae	Quercus robur	1·542	625	4, 28
Angiosperm	Fagales	Fagaceae	Quercus rubra	0·327	277	26
Angiosperm	Fagales	Fagaceae	Quercus suber	0·242	235	83
Angiosperm	Fagales	Fagaceae	Quercus velutina	0·318	269	26
Angiosperm	Fagales	Juglandaceae	Carya cordiformis	0·379	303	26
Angiosperm	Fagales	Juglandaceae	Carya laciniosa	0·407	320	26
Angiosperm	Fagales	Juglandaceae	Carya ovata	0·472	354	26
Angiosperm	Fagales	Juglandaceae	Carya tomentosa	0·425	331	26
Angiosperm	Fagales	Juglandaceae	Juglans cinerea	0·481	357	26
Angiosperm	Fagales	Juglandaceae	Juglans nigra	0·388	306	26
Angiosperm	Fagales	Myricaceae	Myrica cerifera	0·149	187	75, 76
Angiosperm	Garryales	Aucubaceae	Aucuba japonica	0·352	292	83, 86
Angiosperm	Gentianales	Apocynaceae	Cynanchum acutum	0·629	407	19
Angiosperm	Gentianales	Apocynaceae	Nerium oleander	0·416	325	19, 83
Angiosperm	Gentianales	Gentianaceae	Gentiana decumbens	0·529	367	69
Angiosperm	Gentianales	Rubiaceae	Coffea arabica	0·388	307	71
Angiosperm	Gentianales	Rubiaceae	Galium elongatum	0·927	514	19
Angiosperm	Gentianales	Rubiaceae	Galium mollugo	0·088	154	36
Angiosperm	Gentianales	Rubiaceae	Gardenia jasminoides	0·122	176	86
Angiosperm	Gentianales	Rubiaceae	Rubia tinctorum	0·402	315	83
Angiosperm	Geraniales	Geraniaceae	Pelargonium graveolens	0·202	220	83
Angiosperm	Lamiales	Bignoniaceae	Campsis grandiflora	0·042	118	83
Angiosperm	Lamiales	Bignoniaceae	Catalpa ovata	0·262	245	83, 86
Angiosperm	Lamiales	Lamiaceae	Ballota undulata	0·745	466	19
Angiosperm	Lamiales	Lamiaceae	Betonica foliosa	0·879	501	69
Angiosperm	Lamiales	Lamiaceae	Lavandula angustifolia	0·442	340	83
Angiosperm	Lamiales	Lamiaceae	Lycopus europaeus	0·661	429	19
Angiosperm	Lamiales	Lamiaceae	Melissa officinalis	1·084	557	19, 70
Angiosperm	Lamiales	Lamiaceae	Mentha longifolia	0·726	461	19
Angiosperm	Lamiales	Lamiaceae	Mentha piperita	1·220	583	70
Angiosperm	Lamiales	Lamiaceae	Origanum vulgare	0·479	356	69
Angiosperm	Lamiales	Lamiaceae	Plectranthus japonicus	−0·028	69	83
Angiosperm	Lamiales	Lamiaceae	Salvia officinalis	0·562	377	83
Angiosperm	Lamiales	Lamiaceae	Thymus marschallianus	1·949	667	69
Angiosperm	Lamiales	Oleaceae	Fraxinus americana	0·101	159	26, 125
Angiosperm	Lamiales	Oleaceae	Fraxinus oxyphylla	0·684	437	19
Angiosperm	Lamiales	Oleaceae	Ligustrum japonicum	0·192	213	86
Angiosperm	Lamiales	Oleaceae	Ligustrum lucidum	0·172	196	86
Angiosperm	Lamiales	Oleaceae	Olea europaea	0·032	110	83
Angiosperm	Lamiales	Oleaceae	Osmanthus fragrans	0·192	212	86
Angiosperm	Lamiales	Paulowniaceae	Paulownia tomentosa	0·432	332	86
Angiosperm	Lamiales	Plantaginaceae	Plantago lagopus	0·818	482	19
Angiosperm	Lamiales	Plantaginaceae	Plantago lanceolata	0·100	158	18
Angiosperm	Lamiales	Plantaginaceae	Plantago maritima	0·467	352	20
Angiosperm	Lamiales	Scrophulariaceae	Bacopa monnieri	0·752	467	75
Angiosperm	Lamiales	Scrophulariaceae	Kickxia spuria	0·795	479	19
Angiosperm	Lamiales	Scrophulariaceae	Melampyrum pratense	0·678	433	37, 41, 49
Angiosperm	Lamiales	Verbenaceae	Verbena officinalis	0·573	379	19, 83
Angiosperm	Lamiales	Verbenaceae	Vitex agnus-castus	0·819	484	19
Angiosperm	Laurales	Lauraceae	Lindera benzoin	0·294	263	26
Angiosperm	Laurales	Lauraceae	Lindera strychnifolia	−0·008	84	83
Angiosperm	Laurales	Lauraceae	Persea palustris	1·792	655	75
Angiosperm	Laurales	Lauraceae	Sassafras albidum	0·290	259	26
Angiosperm	Liliales	Liliaceae	Lilium leichtlinii	0·012	100	83
Angiosperm	Liliales	Liliaceae	Tricyrtis hirta	0·142	183	83
Angiosperm	Liliales	Melanthiaceae	Heloniopsis orientalis	0·012	101	83
Angiosperm	Magnoliales	Magnoliaceae	Liriodendron tulipifera	0·682	436	86
Angiosperm	Magnoliales	Magnoliaceae	Magnolia grandiflora	0·599	387	76, 83
Angiosperm	Magnoliales	Magnoliaceae	Magnolia hypoleuca	0·622	402	86
Angiosperm	Magnoliales	Magnoliaceae	Magnolia kobus	0·412	324	86
Angiosperm	Malpighiales	Euphorbiaceae	Mallotus japonicus	0·382	304	83
Angiosperm	Malpighiales	Euphorbiaceae	Mercurialis perennis	0·115	167	37, 45
Angiosperm	Malpighiales	Euphorbiaceae	Securinega suffruticosa	0·092	155	83
Angiosperm	Malpighiales	Flacourtiaceae	Idesia polycarpa	0·222	224	86
Angiosperm	Malpighiales	Linaceae	Linum usitatissimum	−0·327	37	93
Angiosperm	Malpighiales	Salicaceae	Populus deltoides	0·696	444	26
Angiosperm	Malpighiales	Salicaceae	Populus euphratica	0·715	456	19
Angiosperm	Malpighiales	Salicaceae	Populus sieboldii	1·781	654	24
Angiosperm	Malpighiales	Salicaceae	Populus tremuloides	0·100	157	6
Angiosperm	Malpighiales	Salicaceae	Salix acmophylla	0·651	421	19
Angiosperm	Malpighiales	Salicaceae	Salix matsudana	0·042	119	83
Angiosperm	Malpighiales	Violaceae	Hybanthus glutinosus	0·172	199	83
Angiosperm	Malpighiales	Violaceae	Viola tricolor	0·032	111	83
Angiosperm	Malvales	Malvaceae	Gossypium hirsutum	0·962	522	16
Angiosperm	Malvales	Malvaceae	Hibiscus cannabinus	0·407	319	8
Angiosperm	Malvales	Malvaceae	Hibiscus moscheutos	1·029	537	79
Angiosperm	Malvales	Malvaceae	Hibiscus sabdariffa	0·597	383	8
Angiosperm	Malvales	Malvaceae	Hibiscus syriacus	0·082	151	83
Angiosperm	Malvales	Malvaceae	Kosteletzkya virginica	0·932	517	74
Angiosperm	Malvales	Malvaceae	Tilia americana	0·486	359	26
Angiosperm	Malvales	Thymelaeaceae	Daphne odora	0·037	114	83, 86
Angiosperm	Myrtales	Lythraceae	Lythrum lineare	0·632	410	74
Angiosperm	Myrtales	Lythraceae	Lythrum salicaria	0·713	454	19
Angiosperm	Myrtales	Melastomataceae	Melastoma candidum	0·082	152	83
Angiosperm	Myrtales	Melastomataceae	Tibouchina pulchra	−0·009	81	88
Angiosperm	Myrtales	Myrtaceae	Callistemon rigidus	−0·008	85	83
Angiosperm	Myrtales	Myrtaceae	Eugenia uniflora	0·061	129	88
Angiosperm	Myrtales	Onagraceae	Chamerion angustifolium	0·325	276	17
Angiosperm	Myrtales	Onagraceae	Epilobium hirsutum	0·655	426	19
Angiosperm	Myrtales	Onagraceae	Ludwigia stolonifera	0·618	398	19
Angiosperm	Myrtales	Onagraceae	Oenothera lamarckiana	−0·018	79	83
Angiosperm	Pandanales	Stemonaceae	Stemona japonica	0·132	180	83
Angiosperm	Piperales	Saururaceae	Houttuynia cordata	1·052	549	83
Angiosperm	Piperales	Saururaceae	Saururus chinensis	0·182	205	83
Angiosperm	Poales	Cyperaceae	Carex aquatilis	−0·788	28	25
Angiosperm	Poales	Cyperaceae	Carex atherodes	1·320	598	6
Angiosperm	Poales	Cyperaceae	Carex biwensis	1·122	566	83
Angiosperm	Poales	Cyperaceae	Carex cinica	2·442	690	83
Angiosperm	Poales	Cyperaceae	Carex curvula	0·784	475	15
Angiosperm	Poales	Cyperaceae	Carex dispalata	2·312	687	83
Angiosperm	Poales	Cyperaceae	Carex filifolia	1·286	592	7, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64
Angiosperm	Poales	Cyperaceae	Carex flacca	0·890	504	18
Angiosperm	Poales	Cyperaceae	Carex flavicans	−0·298	38	25
Angiosperm	Poales	Cyperaceae	Carex parciflora	1·632	640	83
Angiosperm	Poales	Cyperaceae	Carex sempervirens	1·383	609	15
Angiosperm	Poales	Cyperaceae	Carex subspathacea	−0·068	56	25
Angiosperm	Poales	Cyperaceae	Carex thunbergii	1·572	632	83
Angiosperm	Poales	Cyperaceae	Cladium jamaicense	1·412	612	74
Angiosperm	Poales	Cyperaceae	Cladium mariscus	1·503	619	19
Angiosperm	Poales	Cyperaceae	Cyperus alopecuroides	0·788	477	19
Angiosperm	Poales	Cyperaceae	Cyperus alternifolius	3·422	719	83
Angiosperm	Poales	Cyperaceae	Cyperus latifolius	1·023	536	19
Angiosperm	Poales	Cyperaceae	Cyperus michelianus	1·043	545	19
Angiosperm	Poales	Cyperaceae	Cyperus microiria	0·812	480	83
Angiosperm	Poales	Cyperaceae	Cyperus papyrus	1·068	555	19, 71, 83
Angiosperm	Poales	Cyperaceae	Cyperus polystachyos	1·149	576	79
Angiosperm	Poales	Cyperaceae	Cyperus surinamensis	1·379	607	79
Angiosperm	Poales	Cyperaceae	Eleocharis cellulosa	1·562	630	74
Angiosperm	Poales	Cyperaceae	Eleocharis parvula	3·182	713	74
Angiosperm	Poales	Cyperaceae	Eleocharis uniglumis	6·663	733	106
Angiosperm	Poales	Cyperaceae	Fimbristylis spadicea	1·095	560	75, 77
Angiosperm	Poales	Cyperaceae	Rhynchospora plumosa	2·307	686	82
Angiosperm	Poales	Cyperaceae	Scirpus americanus	1·609	639	79
Angiosperm	Poales	Cyperaceae	Scirpus cyperinus	2·057	674	82
Angiosperm	Poales	Cyperaceae	Scirpus olneyi	0·998	529	77
Angiosperm	Poales	Cyperaceae	Scirpus robustus	2·248	683	77
Angiosperm	Poales	Cyperaceae	Scirpus tabernaemontani	0·112	165	83
Angiosperm	Poales	Cyperaceae	Scirpus validus	1·147	575	73
Angiosperm	Poales	Juncaceae	Juncus effusus	0·502	363	83
Angiosperm	Poales	Juncaceae	Juncus gerardii	1·063	552	106
Angiosperm	Poales	Juncaceae	Juncus polycephalus	0·369	300	79
Angiosperm	Poales	Juncaceae	Juncus roemerianus	0·190	211	75, 77
Angiosperm	Poales	Juncaceae	Luzula luzuloides	0·451	342	37, 44, 49
Angiosperm	Poales	Poaceae	Achnatherum hymenoides	1·600	637	12, 13
Angiosperm	Poales	Poaceae	Aegilops squarrosa	2·012	672	83
Angiosperm	Poales	Poaceae	Agropyron cristatum	0·973	526	7
Angiosperm	Poales	Poaceae	Agropyron dasystachyum	0·900	505	6
Angiosperm	Poales	Poaceae	Agropyron repens	1·118	564	36
Angiosperm	Poales	Poaceae	Agropyron smithii	1·187	580	6, 7
Angiosperm	Poales	Poaceae	Agropyron subsecundum	1·090	559	6
Angiosperm	Poales	Poaceae	Agropyron trichophorum	1·143	573	7
Angiosperm	Poales	Poaceae	Agrostis alba	2·132	678	14
Angiosperm	Poales	Poaceae	Agrostis gigantea	3·358	717	36
Angiosperm	Poales	Poaceae	Agrostis palustris	1·055	550	1
Angiosperm	Poales	Poaceae	Agrostis scabra	0·268	251	36
Angiosperm	Poales	Poaceae	Agrostis stolonifera	4·563	729	106
Angiosperm	Poales	Poaceae	Agrostis tenuis	1·034	542	14, 37, 47
Angiosperm	Poales	Poaceae	Andropogon gerardii	1·409	611	27, 80
Angiosperm	Poales	Poaceae	Andropogon scoparius	3·852	722	80
Angiosperm	Poales	Poaceae	Anthoxanthum odoratum	0·613	393	17, 18
Angiosperm	Poales	Poaceae	Aristida stricta	1·038	544	67
Angiosperm	Poales	Poaceae	Arrhenatherum elatius	0·880	502	18
Angiosperm	Poales	Poaceae	Arundinaria gigantea	8·769	735	79
Angiosperm	Poales	Poaceae	Arundo donax	1·454	614	8, 83
Angiosperm	Poales	Poaceae	Avena sativa	1·513	622	5, 29, 30, 65, 83, 85, 93, 94, 95, 96
Angiosperm	Poales	Poaceae	Bouteloua curtipendula	1·714	647	97
Angiosperm	Poales	Poaceae	Bouteloua gracilis	1·144	574	7, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 97
Angiosperm	Poales	Poaceae	Bouteloua hirsuta	2·194	680	97
Angiosperm	Poales	Poaceae	Brachypodium pinnatum	0·960	521	18
Angiosperm	Poales	Poaceae	Brachypodium sylvaticum	3·105	712	37, 45, 47, 51
Angiosperm	Poales	Poaceae	Briza media	0·880	503	18
Angiosperm	Poales	Poaceae	Bromus inermis	1·303	595	6, 36, 91
Angiosperm	Poales	Poaceae	Bromus pumpellianus	0·920	513	6
Angiosperm	Poales	Poaceae	Bromus tectorum	1·475	615	12, 13, 91
Angiosperm	Poales	Poaceae	Calamagrostis canadensis	1·768	652	36
Angiosperm	Poales	Poaceae	Calamagrostis epigejos	2·249	684	37, 38, 45, 48
Angiosperm	Poales	Poaceae	Calamagrostis inexpansa	1·830	658	6
Angiosperm	Poales	Poaceae	Calamagrostis rubescens	1·590	634	6
Angiosperm	Poales	Poaceae	Calamagrostis villosa	2·689	702	15, 37, 44, 45
Angiosperm	Poales	Poaceae	Cenchrus longispinus	1·382	608	81
Angiosperm	Poales	Poaceae	Chasmanthium latifolium	4·127	725	82
Angiosperm	Poales	Poaceae	Chasmanthium sessiliflorum	0·707	448	82
Angiosperm	Poales	Poaceae	Cornucopiae cucullatum	0·931	516	Aegilopssquarrosa
Angiosperm	Poales	Poaceae	Cortaderia selloana	0·579	382	82, 83
Angiosperm	Poales	Poaceae	Ctenium aromaticum	3·039	710	79
Angiosperm	Poales	Poaceae	Cymbopogon citratus	0·752	468	83
Angiosperm	Poales	Poaceae	Cynodon dactylon	1·509	621	1, 14, 72, 98, 99, 100, 101, 102
Angiosperm	Poales	Poaceae	Dactylis glomerata	0·600	389	18
Angiosperm	Poales	Poaceae	Danthonia intermedia	1·490	617	6
Angiosperm	Poales	Poaceae	Danthonia parryi	1·270	588	6
Angiosperm	Poales	Poaceae	Deschampsia cespitosa	1·377	605	6, 37, 42, 44, 47, 54, 55
Angiosperm	Poales	Poaceae	Deschampsia flexuosa	0·628	406	17, 37, 40, 43, 44, 46, 49, 50
Angiosperm	Poales	Poaceae	Digitaria decumbens	0·457	348	85
Angiosperm	Poales	Poaceae	Digitaria ischaemum	2·762	705	14
Angiosperm	Poales	Poaceae	Distichlis spicata	1·598	635	73, 77
Angiosperm	Poales	Poaceae	Echinochloa colona	0·850	495	19
Angiosperm	Poales	Poaceae	Echinochloa crus-galli	1·377	606	75, 81
Angiosperm	Poales	Poaceae	Ehrharta erecta	0·785	476	1
Angiosperm	Poales	Poaceae	Elymus cinereus	1·030	539	6
Angiosperm	Poales	Poaceae	Elymus elymoides	1·325	600	12, 13
Angiosperm	Poales	Poaceae	Elymus innovatus	1·050	548	6
Angiosperm	Poales	Poaceae	Elymus junceus	1·177	578	6, 7
Angiosperm	Poales	Poaceae	Elymus mollis	0·852	496	83
Angiosperm	Poales	Poaceae	Elymus virginicus	2·369	688	79
Angiosperm	Poales	Poaceae	Elytrigia atherica	1·947	666	20
Angiosperm	Poales	Poaceae	Eragrostis curvula	0·827	485	8
Angiosperm	Poales	Poaceae	Festuca arundinacea	1·308	596	14, 19, 87, 92, 98, 99, 100, 101, 102, 104, 105
Angiosperm	Poales	Poaceae	Festuca gigantea	2·264	685	37, 42, 45
Angiosperm	Poales	Poaceae	Festuca halleri	1·845	660	15
Angiosperm	Poales	Poaceae	Festuca idahoensis	1·730	649	6
Angiosperm	Poales	Poaceae	Festuca ovina	0·643	416	17, 18
Angiosperm	Poales	Poaceae	Festuca pratensis	1·043	546	87, 92, 104, 105
Angiosperm	Poales	Poaceae	Festuca puccinellii	1·687	645	15
Angiosperm	Poales	Poaceae	Festuca rubra	1·113	563	1, 6, 14, 20, 25
Angiosperm	Poales	Poaceae	Festuca scabrella	1·288	593	6, 54, 55
Angiosperm	Poales	Poaceae	Festuca scabriculmis	1·481	616	15
Angiosperm	Poales	Poaceae	Festuca sylvatica	2·919	708	2
Angiosperm	Poales	Poaceae	Helictotrichon pratense	0·908	509	17, 18
Angiosperm	Poales	Poaceae	Hilaria jamesii	1·494	618	97
Angiosperm	Poales	Poaceae	Hilaria rigida	1·809	656	123, 124
Angiosperm	Poales	Poaceae	Holcus lanatus	0·860	497	18
Angiosperm	Poales	Poaceae	Hordeum vulgare	1·824	657	9, 29, 30, 85, 93, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124
Angiosperm	Poales	Poaceae	Imperata cylindrica	1·137	571	82
Angiosperm	Poales	Poaceae	Koeleria cristata	1·063	553	7
Angiosperm	Poales	Poaceae	Lolium perenne	3·644	721	14, 89
Angiosperm	Poales	Poaceae	Lolium rigidum	0·970	525	30, 31, 31, 65
Angiosperm	Poales	Poaceae	Lycurus phleoides	1·014	533	97
Angiosperm	Poales	Poaceae	Manisuris rugosa	3·623	720	78
Angiosperm	Poales	Poaceae	Melica uniflora	1·844	659	37
Angiosperm	Poales	Poaceae	Melinis minutiflora	0·457	347	85
Angiosperm	Poales	Poaceae	Miscanthus sinensis	2·862	706	83
Angiosperm	Poales	Poaceae	Molinia caerulea	1·167	577	38, 39, 48
Angiosperm	Poales	Poaceae	Muhlenbergia richardsonis	2·504	693	97
Angiosperm	Poales	Poaceae	Nardus stricta	1·551	628	15
Angiosperm	Poales	Poaceae	Oryza sativa	4·167	726	83, 85, 107, 108, 109, 110
Angiosperm	Poales	Poaceae	Oryzopsis asperifolia	1·118	565	36
Angiosperm	Poales	Poaceae	Panicum amarum	0·833	490	78
Angiosperm	Poales	Poaceae	Panicum commutatum	4·227	727	82
Angiosperm	Poales	Poaceae	Panicum maximum	0·547	374	85
Angiosperm	Poales	Poaceae	Panicum obtusum	1·134	570	97
Angiosperm	Poales	Poaceae	Panicum repens	1·030	538	78, 82
Angiosperm	Poales	Poaceae	Panicum texanum	8·027	734	8
Angiosperm	Poales	Poaceae	Panicum virgatum	2·012	671	8, 27, 74, 80
Angiosperm	Poales	Poaceae	Paspalum dilatatum	1·655	643	1
Angiosperm	Poales	Poaceae	Paspalum urvillei	2·062	675	81
Angiosperm	Poales	Poaceae	Paspalum vaginatum	0·688	439	19
Angiosperm	Poales	Poaceae	Paspalum wettsteinii	0·597	386	85
Angiosperm	Poales	Poaceae	Pennisetum clandestinum	0·939	518	1, 88
Angiosperm	Poales	Poaceae	Phalaris arundinacea	2·521	695	87
Angiosperm	Poales	Poaceae	Phalaris tuberosa	1·667	644	85
Angiosperm	Poales	Poaceae	Phleum pratense	0·837	494	6, 36, 93
Angiosperm	Poales	Poaceae	Phragmites australis	0·978	527	19
Angiosperm	Poales	Poaceae	Phragmites communis	2·739	703	79
Angiosperm	Poales	Poaceae	Pleioblastus chino	5·072	730	83
Angiosperm	Poales	Poaceae	Poa chaixii	0·474	355	37, 51
Angiosperm	Poales	Poaceae	Poa compressa	0·648	420	36
Angiosperm	Poales	Poaceae	Poa pratensis	1·543	626	14, 98, 99, 100, 101, 102, 103
Angiosperm	Poales	Poaceae	Poa secunda	1·343	602	7
Angiosperm	Poales	Poaceae	Puccinellia maritima	0·597	384	20
Angiosperm	Poales	Poaceae	Puccinellia phryganodes	−0·978	25	25
Angiosperm	Poales	Poaceae	Saccharum officinarum	1·509	620	79, 83, 107, 108
Angiosperm	Poales	Poaceae	Sasa nipponica	3·234	714	24, 83
Angiosperm	Poales	Poaceae	Secale cereale	1·256	586	29, 65, 83, 91, 93
Angiosperm	Poales	Poaceae	Setaria geniculata	1·652	642	81
Angiosperm	Poales	Poaceae	Setaria italica	0·916	512	10, 11
Angiosperm	Poales	Poaceae	Setaria magna	3·337	716	82
Angiosperm	Poales	Poaceae	Setaria sphacelata	−0·103	46	85
Angiosperm	Poales	Poaceae	Sorghastrum nutans	1·999	670	27, 80
Angiosperm	Poales	Poaceae	Sorghum bicolor	1·539	624	10, 11, 21, 22
Angiosperm	Poales	Poaceae	Sorghum halepense	0·999	531	79
Angiosperm	Poales	Poaceae	Spartina alterniflora	0·653	425	73, 77
Angiosperm	Poales	Poaceae	Spartina anglica	1·567	631	20
Angiosperm	Poales	Poaceae	Spartina cynosuroides	1·129	569	74, 82
Angiosperm	Poales	Poaceae	Spartina patens	0·780	474	74, 77
Angiosperm	Poales	Poaceae	Sporobolus cryptandrus	0·714	455	97
Angiosperm	Poales	Poaceae	Stipa comata	0·697	445	7, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 80
Angiosperm	Poales	Poaceae	Stipa richardsonii	1·280	591	6
Angiosperm	Poales	Poaceae	Stipa spartea	1·321	599	6, 80
Angiosperm	Poales	Poaceae	Stipa viridula	1·640	641	6
Angiosperm	Poales	Poaceae	Trichachne californica	1·527	623	8
Angiosperm	Poales	Poaceae	Tripsacum dactyloides	0·903	507	78
Angiosperm	Poales	Poaceae	Triticosecale spp.	0·131	178	9
Angiosperm	Poales	Poaceae	Triticum aestivum	2·455	692	9, 16, 29, 83, 85, 89, 91, 93, 94, 95, 96, 107, 108, 109, 110
Angiosperm	Poales	Poaceae	Triticum boeoticum	2·512	694	83
Angiosperm	Poales	Poaceae	Triticum dicoccoides	1·232	584	83
Angiosperm	Poales	Poaceae	Triticum percicumx	1·602	638	83
Angiosperm	Poales	Poaceae	Uniola paniculata	0·836	491	78, 79
Angiosperm	Poales	Poaceae	Zea mays	0·827	486	21, 22, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122
Angiosperm	Poales	Poaceae	Zizania aquatica	2·625	698	73, 78
Angiosperm	Poales	Poaceae	Zizaniopsis miliacea	3·913	723	78
Angiosperm	Poales	Poaceae	Zoysia japonica	0·312	267	14
Angiosperm	Poales	Typhaceae	Typha angustata	0·651	422	19
Angiosperm	Poales	Typhaceae	Typha angustifolia	0·222	226	75
Angiosperm	Proteales	Platanaceae	Platanus occidentalis	0·453	344	26
Angiosperm	Ranunculales	Berberidaceae	Epimedium grandiflorum	0·292	262	83
Angiosperm	Ranunculales	Berberidaceae	Nandina domestica	0·067	139	83, 86
Angiosperm	Ranunculales	Papaveraceae	Papaver bracteatum	0·652	423	83
Angiosperm	Ranunculales	Papaveraceae	Papaver rhoeas	0·482	358	83
Angiosperm	Ranunculales	Ranunculaceae	Aconitum japonicum	0·252	241	83
Angiosperm	Ranunculales	Ranunculaceae	Aconitum loczyanum	0·222	228	83
Angiosperm	Ranunculales	Ranunculaceae	Aquilegia flabellata	−0·048	62	83
Angiosperm	Ranunculales	Ranunculaceae	Eranthis giganteus	1·939	665	79
Angiosperm	Ranunculales	Ranunculaceae	Pulsatilla multifida	0·679	435	69
Angiosperm	Ranunculales	Ranunculaceae	Ranunculus japonicus	0·262	246	83
Angiosperm	Rosales	Cannabaceae	Cannabis sativa	−0·285	39	93
Angiosperm	Rosales	Celtidaceae	Celtis occidentalis	2·652	700	26, 125
Angiosperm	Rosales	Elaeagnaceae	Hippophae rhamnoides	2·079	676	69
Angiosperm	Rosales	Elaeagnaceae	Elaeagnus multiflora	0·062	135	83
Angiosperm	Rosales	Moraceae	Ficus lyrata	1·728	648	71
Angiosperm	Rosales	Moraceae	Maclura pomifera	0·818	483	26
Angiosperm	Rosales	Moraceae	Morus alba	0·552	375	83
Angiosperm	Rosales	Moraceae	Morus rubra	1·884	662	26, 79
Angiosperm	Rosales	Rosaceae	Aronia melanocarpa	1·179	579	69
Angiosperm	Rosales	Rosaceae	Chaenomeles sinensis	0·192	214	83
Angiosperm	Rosales	Rosaceae	Crataegus cuneata	0·012	102	83
Angiosperm	Rosales	Rosaceae	Fallugia paradoxa	0·457	345	8
Angiosperm	Rosales	Rosaceae	Kerria japonica	0·232	233	83
Angiosperm	Rosales	Rosaceae	Potentilla erecta	0·909	511	69
Angiosperm	Rosales	Rosaceae	Potentilla fruticosa	0·120	172	6
Angiosperm	Rosales	Rosaceae	Prunus serotina	0·276	255	26
Angiosperm	Rosales	Rosaceae	Prunus virginiana	0·500	362	26
Angiosperm	Rosales	Rosaceae	Pyracantha crenulata	−0·008	86	83
Angiosperm	Rosales	Rosaceae	Rosa woodsii	0·290	258	6
Angiosperm	Rosales	Rosaceae	Rubus idaeus	0·067	140	37, 42, 44, 45, 47
Angiosperm	Rosales	Rosaceae	Spiraea thunbergii	0·062	136	83
Angiosperm	Rosales	Ulmaceae	Ulmus americana	2·038	673	26, 72
Angiosperm	Rosales	Ulmaceae	Ulmus rubra	1·257	587	26
Angiosperm	Rosales	Urticaceae	Urtica dioica	1·335	601	17, 37, 42, 45, 47
Angiosperm	Rosales	Urticaceae	Urtica hulensis	0·690	441	19
Angiosperm	Santalales	Loranthaceae	Struthanthus marginatus	0·104	162	88
Angiosperm	Sapindales	Meliaceae	Guarea macrophylla	0·071	144	88
Angiosperm	Sapindales	Meliaceae	Melia azedarach	0·172	200	83
Angiosperm	Sapindales	Rutaceae	Phellodendron amurense	0·302	264	83
Angiosperm	Sapindales	Rutaceae	Poncirus trifoliata	0·392	309	83
Angiosperm	Sapindales	Rutaceae	Zanthoxylum americanum	0·463	350	26
Angiosperm	Sapindales	Rutaceae	Zanthoxylum piperitum	0·262	247	83
Angiosperm	Sapindales	Sapindaceae	Acer ginnala	0·432	334	83
Angiosperm	Sapindales	Sapindaceae	Acer negundo	0·416	326	26
Angiosperm	Sapindales	Sapindaceae	Acer rubrum	0·902	506	75
Angiosperm	Sapindales	Sapindaceae	Acer saccharinum	0·715	457	26
Angiosperm	Sapindales	Sapindaceae	Acer saccharum	1·124	567	26, 83
Angiosperm	Sapindales	Sapindaceae	Aesculus pavia	0·186	208	76
Angiosperm	Sapindales	Sapindaceae	Cupania oblongifolia	0·106	163	88
Angiosperm	Saxifragales	Cercidiphyllaceae	Cercidiphyllum japonicum	0·597	385	83, 86
Angiosperm	Saxifragales	Crassulaceae	Kalanchöe braziliensis	0·009	98	88
Angiosperm	Saxifragales	Crassulaceae	Rhodiola linearifolia	2·679	701	69
Angiosperm	Saxifragales	Crassulaceae	Sedum hybridum	3·329	715	69
Angiosperm	Saxifragales	Hamamelidaceae	Corylopsis pauciflora	0·142	181	86
Angiosperm	Solanales	Convolvulaceae	Calystegia japonica	−0·078	51	83
Angiosperm	Solanales	Convolvulaceae	Calystegia sepium	0·617	396	19
Angiosperm	Solanales	Convolvulaceae	Cuscuta planiflora	0·633	411	19
Angiosperm	Solanales	Convolvulaceae	Cuscuta racemosa	−0·006	88	88
Angiosperm	Solanales	Convolvulaceae	Ipomoea sagittata	0·532	369	74
Angiosperm	Solanales	Solanaceae	Atropa belladonna	−0·068	55	83
Angiosperm	Solanales	Solanaceae	Capsicum annuum	−0·003	89	103
Angiosperm	Solanales	Solanaceae	Lycopersicon esculentum	1·545	627	109, 110
Angiosperm	Solanales	Solanaceae	Physalis alkekengi	0·002	96	83
Angiosperm	Solanales	Solanaceae	Solanum americanum	0·145	186	88
Angiosperm	Solanales	Solanaceae	Solanum nigrum	0·637	413	19
Angiosperm	unassigned to order	Boraginaceae	Echium angustifolium	1·086	558	19
Angiosperm	unassigned to order	Boraginaceae	Heliotropium supinum	0·766	470	19
Angiosperm	unassigned to order	Bromeliaceae	Ananas comosus	0·142	184	83
Angiosperm	unassigned to order	Bromeliaceae	Tillandsia usneoides	0·256	242	76
Angiosperm	unassigned to order	Celastraceae	Euonymus japonicus	0·152	190	86
Angiosperm	unassigned to order	Nymphaeaceae	Nuphar lutea	0·685	438	19
Angiosperm	unassigned to order	Schisandraceae	Schisandra chinensis	1·209	582	69
Angiosperm	unassigned to order	Staphyleaceae	Staphylea trifolia	0·397	313	26
Angiosperm	unassigned to order	Vitaceae	Vitis aestivalis	0·206	222	76
Angiosperm	Zingiberales	Cannaceae	Canna indica	0·262	248	83
Angiosperm	Zingiberales	Musaceae	Musa basjoo	0·982	528	83
Angiosperm	Zingiberales	Zingiberaceae	Renealmia petasites	0·402	316	88
Angiosperm	Zingiberales	Zingiberaceae	Zingiber mioga	0·122	177	83
Bryophyta (mosses)	Sphagnales	Sphagnaceae	Sphagnum cymbifolium	1·272	589	83
Equisetophyta	Equisetales	Equisetaceae	Equisetum arvense	3·992	724	83, 84
Equisetophyta	Equisetales	Equisetaceae	Equisetum hyemale	2·917	707	83, 84
Gymnosperm	Cycadales	Cycadaceae	Cycas revoluta	−0·028	70	83
Gymnosperm	Ephedrales	Ephedraceae	Ephedra sinica	−0·078	52	83
Gymnosperm	Ginkgoales	Ginkgoaceae	Ginkgo biloba	−0·048	63	83
Gymnosperm	Pinales	Araucariaceae	Araucaria araucana	0·403	318	35
Gymnosperm	Pinales	Cupressaceae	Chamaecyparis lawsoniana	0·871	499	35
Gymnosperm	Pinales	Cupressaceae	Chamaecyparis obtusa	0·269	252	35, 83
Gymnosperm	Pinales	Cupressaceae	Chamaecyparis pisifera	0·375	302	35
Gymnosperm	Pinales	Cupressaceae	Chamaecyparis thyoides	0·929	515	79
Gymnosperm	Pinales	Cupressaceae	Cupressocyparis leylandii	0·815	481	35
Gymnosperm	Pinales	Cupressaceae	Cupressus sempervirens	0·002	97	83
Gymnosperm	Pinales	Cupressaceae	Juniperus communis	0·025	107	35
Gymnosperm	Pinales	Cupressaceae	Juniperus nana	0·340	279	15
Gymnosperm	Pinales	Cupressaceae	Juniperus virginiana	0·096	156	76
Gymnosperm	Pinales	Cupressaceae	Thuja orientalis	0·068	142	35, 83
Gymnosperm	Pinales	Pinaceae	Abies alba	0·340	280	15
Gymnosperm	Pinales	Pinaceae	Abies balsamea	0·198	217	68
Gymnosperm	Pinales	Pinaceae	Abies fraseri	0·173	201	68
Gymnosperm	Pinales	Pinaceae	Abies grandis	0·399	314	35
Gymnosperm	Pinales	Pinaceae	Abies mariesii	0·062	137	35
Gymnosperm	Pinales	Pinaceae	Abies nordmanniana	0·188	209	35
Gymnosperm	Pinales	Pinaceae	Abies pectinata	4·512	728	2, 3
Gymnosperm	Pinales	Pinaceae	Abies procera	0·441	336	35
Gymnosperm	Pinales	Pinaceae	Cedrus atlantica	0·048	121	35
Gymnosperm	Pinales	Pinaceae	Larix decidua	0·869	498	15, 35, 68
Gymnosperm	Pinales	Pinaceae	Larix laricina	0·224	229	68
Gymnosperm	Pinales	Pinaceae	Picea abies	1·363	604	15, 28, 35
Gymnosperm	Pinales	Pinaceae	Picea glauca	0·533	370	33, 34, 68
Gymnosperm	Pinales	Pinaceae	Picea mariana	0·192	215	68
Gymnosperm	Pinales	Pinaceae	Picea orientalis	1·016	534	35
Gymnosperm	Pinales	Pinaceae	Picea rubens	0·316	268	68
Gymnosperm	Pinales	Pinaceae	Pinus armandii	0·198	216	35
Gymnosperm	Pinales	Pinaceae	Pinus banksiana	0·199	218	68
Gymnosperm	Pinales	Pinaceae	Pinus cembra	0·364	298	15
Gymnosperm	Pinales	Pinaceae	Pinus clausa	0·643	417	66
Gymnosperm	Pinales	Pinaceae	Pinus contorta	0·057	128	35
Gymnosperm	Pinales	Pinaceae	Pinus cooperi	0·347	287	35
Gymnosperm	Pinales	Pinaceae	Pinus flexilis	0·067	141	35
Gymnosperm	Pinales	Pinaceae	Pinus jeffreyi	0·020	104	35
Gymnosperm	Pinales	Pinaceae	Pinus koraiensis	0·202	221	35
Gymnosperm	Pinales	Pinaceae	Pinus luchuensis	−0·018	80	83
Gymnosperm	Pinales	Pinaceae	Pinus mugo	0·350	289	15
Gymnosperm	Pinales	Pinaceae	Pinus palustris	0·310	266	67, 83
Gymnosperm	Pinales	Pinaceae	Pinus parviflora	0·118	169	35
Gymnosperm	Pinales	Pinaceae	Pinus peuce	0·048	122	35
Gymnosperm	Pinales	Pinaceae	Pinus pinea	0·011	99	35
Gymnosperm	Pinales	Pinaceae	Pinus resinosa	0·152	193	68
Gymnosperm	Pinales	Pinaceae	Pinus strobiformis	0·034	112	35
Gymnosperm	Pinales	Pinaceae	Pinus strobus	0·119	170	33, 34, 35, 68
Gymnosperm	Pinales	Pinaceae	Pinus sylvestris	0·261	244	3, 4, 28, 35, 68
Gymnosperm	Pinales	Pinaceae	Pseudolarix amabilis	0·034	113	35
Gymnosperm	Pinales	Pinaceae	Pseudotsuga flauhauti	0·184	207	35
Gymnosperm	Pinales	Pinaceae	Pseudotsuga macrolepis	0·908	510	35
Gymnosperm	Pinales	Pinaceae	Pseudotsuga menziesii	0·319	270	35, 68
Gymnosperm	Pinales	Pinaceae	Tsuga canadensis	0·159	195	35, 68
Gymnosperm	Pinales	Pinaceae	Tsuga caroliniana	0·178	202	68
Gymnosperm	Pinales	Pinaceae	Tsuga diversifolia	0·385	305	35
Gymnosperm	Pinales	Pinaceae	Tsuga heterophylla	0·114	166	35
Gymnosperm	Pinales	Podocarpaceae	Podocarpus neriifolius	0·368	299	71
Gymnosperm	Pinales	Taxodiaceae	Cryptomeria japonica	0·066	138	35, 83
Gymnosperm	Pinales	Taxodiaceae	Cunninghamia lanceolata	−0·002	90	35, 83
Gymnosperm	Pinales	Taxodiaceae	Sequoia sempervirens	0·142	185	83
Gymnosperm	Pinales	Taxodiaceae	Sequoiadendron giganteum	0·188	210	35
Gymnosperm	Pinales	Taxodiaceae	Taxodium distichum	0·043	120	35
Gymnosperm	Pinales	Taxodiaceae	Taxodium japonicum	1·557	629	24
Gymnosperm	Taxales	Taxaceae	Taxus baccata	0·083	153	35
Gymnosperm	Taxales	Taxaceae	Taxus cuspidata	0·244	237	35
Gymnosperm	Taxales	Taxaceae	Torreya nucifera	0·012	103	83
Lycopodiophyta (clubmosses)	Lycopodiales	Lycopodiaceae	Lycopodium carolinianum	1·033	541	78
Lycopodiophyta (clubmosses)	Lycopodiales	Lycopodiaceae	Lycopodium clavatum	0·542	372	83
Lycopodiophyta (clubmosses)	Selaginellales	Selaginellaceae	Selaginella caulescens	1·967	669	83, 84
Lycopodiophyta (clubmosses)	Selaginellales	Selaginellaceae	Selaginella involvens	2·117	677	83, 84
Lycopodiophyta (clubmosses)	Selaginellales	Selaginellaceae	Selaginella uncinata	1·742	651	83
Marchantiophyta (liverworts)	Marchantiales	Marchantiaceae	Marchantia polymorpha	5·452	731	83
Polypodiophyta (true ferns)	Aspleniales	Aspleniaceae	Asplenium cuneifolium	0·053	126	52
Polypodiophyta (true ferns)	Aspleniales	Aspleniaceae	Asplenium trichomanes	−0·008	87	83
Polypodiophyta (true ferns)	Aspleniales	Blechnaceae	Blechnum amabile	0·832	489	83
Polypodiophyta (true ferns)	Aspleniales	Blechnaceae	Blechnum spicant	2·418	689	52, 53
Polypodiophyta (true ferns)	Aspleniales	Blechnaceae	Woodwardia orientalis	0·181	203	84
Polypodiophyta (true ferns)	Aspleniales	Davalliaceae	Davallia mariesii	−1·709	20	84
Polypodiophyta (true ferns)	Aspleniales	Dryopteridaceae	Acrophorus stipellatus	−1·039	24	84
Polypodiophyta (true ferns)	Aspleniales	Dryopteridaceae	Cyrtomium falcatum	−2·039	5	84
Polypodiophyta (true ferns)	Aspleniales	Dryopteridaceae	Cyrtomium fortunei	−1·939	11	84
Polypodiophyta (true ferns)	Aspleniales	Dryopteridaceae	Dryopteris bissetiana	−2·109	2	84
Polypodiophyta (true ferns)	Aspleniales	Dryopteridaceae	Dryopteris carthusiana	0·183	206	52, 53
Polypodiophyta (true ferns)	Aspleniales	Dryopteridaceae	Dryopteris crassirhizoma	−2·029	6	84
Polypodiophyta (true ferns)	Aspleniales	Dryopteridaceae	Dryopteris erythrosora	−1·959	9	84
Polypodiophyta (true ferns)	Aspleniales	Dryopteridaceae	Dryopteris filix-mas	0·070	143	37, 38, 42, 44, 45, 47, 52, 53
Polypodiophyta (true ferns)	Aspleniales	Dryopteridaceae	Dryopteris lacera	−1·979	7	84
Polypodiophyta (true ferns)	Aspleniales	Dryopteridaceae	Dryopteris sieboldii	−1·899	14	84
Polypodiophyta (true ferns)	Aspleniales	Dryopteridaceae	Dryopteris uniformis	−1·929	12	84
Polypodiophyta (true ferns)	Aspleniales	Dryopteridaceae	Polystichopsis amabilis	−1·839	18	84
Polypodiophyta (true ferns)	Aspleniales	Dryopteridaceae	Polystichopsis pseudo-aristata	−1·879	16	84
Polypodiophyta (true ferns)	Aspleniales	Dryopteridaceae	Polystichopsis standishii	−1·959	10	84
Polypodiophyta (true ferns)	Aspleniales	Dryopteridaceae	Polystichum lepidocaulon	−2·109	3	84
Polypodiophyta (true ferns)	Aspleniales	Dryopteridaceae	Polystichum polyblepharum	−2·099	4	84
Polypodiophyta (true ferns)	Aspleniales	Dryopteridaceae	Polystichum pseudo-makinoi	−1·799	19	84
Polypodiophyta (true ferns)	Aspleniales	Dryopteridaceae	Polystichum tripteron	−1·979	8	84
Polypodiophyta (true ferns)	Aspleniales	Dryopteridaceae	Ctenitis subglandulosa	−1·679	21	84
Polypodiophyta (true ferns)	Aspleniales	Oleandraceae	Nephrolepis cordifolia	−1·899	15	84
Polypodiophyta (true ferns)	Aspleniales	Thelypteridaceae	Cyclosorus acuminatus	1·101	561	84
Polypodiophyta (true ferns)	Aspleniales	Thelypteridaceae	Cyclosorus dentatus	2·941	709	84
Polypodiophyta (true ferns)	Aspleniales	Thelypteridaceae	Lastrea limbosperma	0·968	524	52, 53
Polypodiophyta (true ferns)	Aspleniales	Thelypteridaceae	Lastrea oligophlebia	−0·949	26	84
Polypodiophyta (true ferns)	Aspleniales	Thelypteridaceae	Leptogramma mollissima	0·831	488	84
Polypodiophyta (true ferns)	Aspleniales	Thelypteridaceae	Phegopteris connectilis	2·643	699	52
Polypodiophyta (true ferns)	Aspleniales	Woodsiaceae	Athyrium filix-femina	1·352	603	37, 42, 44, 45, 47, 52, 53
Polypodiophyta (true ferns)	Aspleniales	Woodsiaceae	Athyrium japonicum	−0·949	27	84
Polypodiophyta (true ferns)	Aspleniales	Woodsiaceae	Athyrium lobato-crenatum	−0·259	41	84
Polypodiophyta (true ferns)	Aspleniales	Woodsiaceae	Athyrium niponicum	−1·199	22	84
Polypodiophyta (true ferns)	Aspleniales	Woodsiaceae	Athyrium yokoscense	−0·739	29	84
Polypodiophyta (true ferns)	Aspleniales	Woodsiaceae	Diplazium hachijoense	2·221	681	84
Polypodiophyta (true ferns)	Aspleniales	Woodsiaceae	Diplazium wichurae	−0·499	33	84
Polypodiophyta (true ferns)	Aspleniales	Woodsiaceae	Gymnocarpium dryopteris	2·153	679	52
Polypodiophyta (true ferns)	Aspleniales	Woodsiaceae	Matteuccia struthiopteris	1·933	664	52, 53
Polypodiophyta (true ferns)	Aspleniales	Woodsiaceae	Struthiopteris niponica	3·072	711	83
Polypodiophyta (true ferns)	Aspleniales	Woodsiaceae	Onoclea sensibilis	−0·629	30	84
Polypodiophyta (true ferns)	Gleicheniales	Gleicheniaceae	Gleichenia glauca	0·692	442	83
Polypodiophyta (true ferns)	Marattiales	Marattiaceae	Angiopteris lygodiifolia	−0·509	32	84
Polypodiophyta (true ferns)	Osmundales	Osmundaceae	Osmunda cinnamomea	0·953	520	53
Polypodiophyta (true ferns)	Osmundales	Osmundaceae	Osmunda gracilis	1·137	572	53, 74
Polypodiophyta (true ferns)	Osmundales	Osmundaceae	Osmunda japonica	3·421	718	84
Polypodiophyta (true ferns)	Osmundales	Osmundaceae	Osmunda lancea	0·251	240	84
Polypodiophyta (true ferns)	Parkeriales	Adiantaceae	Adiantum pedatum	0·232	232	83, 84
Polypodiophyta (true ferns)	Parkeriales	Dennstaedtiaceae	Dennstaedtia scabra	−0·269	40	84
Polypodiophyta (true ferns)	Parkeriales	Dennstaedtiaceae	Pteridium aquilinum	1·299	594	37, 39, 41, 48, 52, 53, 84
Polypodiophyta (true ferns)	Parkeriales	Pteridaceae	Pteris ensiformis	−0·539	31	84
Polypodiophyta (true ferns)	Polypodiales	Polypodiaceae	Colysis decurrens	−1·869	17	84
Polypodiophyta (true ferns)	Polypodiales	Polypodiaceae	Colysis wrightii	−2·139	1	84
Polypodiophyta (true ferns)	Polypodiales	Polypodiaceae	Loxogramme saziran	0·022	106	83
Polypodiophyta (true ferns)	Polypodiales	Polypodiaceae	Polypodium vulgare	0·153	194	52, 53
Polypodiophyta (true ferns)	Polypodiales	Polypodiaceae	Pyrrosia lingua	−1·089	23	83, 84
Polypodiophyta (true ferns)	Schizaeales	Schizaeaceae	Lygodium japonicum	1·102	562	83

Data are from 125 studies, contained in 54 papers in the primary literature, in which Si concentrations of leaf or non-woody shoot tissue were reported. Each study included at least two plant species growing in the same environment, and each study contained at least one species in common with another study. A residual maximum likelihood procedure was performed on the 1066 linked data to estimate the mean relative shoot Si concentration of species, adjusted for differences between studies.

Table 2.

Variance components model of shoot Si concentrations, based on a meta-analysis of primary data from 125 studies, contained in 54 papers in the primary literature, in which Si concentrations of leaf or non-woody shoot tissue were reported

Variance component	Variance	s.e.	% of total variance
Study	0·815	0·128	16·0
Group	3·409	2·204	66·9
Group/order	0·019	0·032	0·4
Group/order/family	0·127	0·044	2·5
Group/order/family/genus	0·102	0·039	2·0
Group/order/family/genus/species	0·072	0·044	1·4
Residual variance model	0·550	0·040	10·8

Each study included at least two plant species growing in the same environment, and each study contained at least one species in common with another study.

Across all plant species, relative shoot Si concentration varied from −2·139 in Colysis wrightii (Polypodiaceae) to 8·769 in Arundinaria gigantea (Poaceae); the mean was 0·722 (Table 1 and Fig. 1). Negative relative shoot Si concentration values can arise as a consequence of adjusting for between-study variation during REML fitting procedures. Mean relative shoot Si concentrations of some fern species from the study of Ma and Takahashi (2002) formed a distinct distribution peak in the low relative shoot Si concentration range (Fig. 1, inset). However, since the mean relative shoot Si concentrations adjusted for differences between studies using the REML procedure corresponded closely to the arithmetic mean shoot Si concentration across all studies (Fig. 2), and since there was a minimal ‘study’ variance component (Table 2), data from Ma and Takahashi (2002) were retained in subsequent analyses.

Fig. 1.

Ranked mean relative shoot Si concentration in 735 species of plants based on data from 125 independent studies in 54 papers in the primary literature. A residual maximum likelihood (REML) procedure was used to adjust for differences in shoot Si concentration between studies. Data are ranked and presented as a frequency distribution (inset). Species names and study references are given in Table 1 and the Appendix.

Fig. 2.

The arithmetic mean shoot Si concentration as a function of mean relative shoot Si concentration, adjusted for differences in shoot Si concentration between studies using a residual maximum likelihood (REML) procedure. Data are based on 125 independent studies in 54 papers in the primary literature.

Mean relative shoot Si concentrations differed significantly between the seven groups of plant species [one-way ANOVA, F_6,728 = 18·11, P < 0·001, residual mean square (r.m.s.) = 1·053; Fig. 3]. Shoot Si concentration declined in the order liverworts > horsetails > clubmosses >mosses > angiosperms > gymnosperms > ferns. Notable Si accumulators included Equisetaceae species Equisetum arvense (3·992) and Equisetum hyemale (2·917). However, non-vascular plant species were poorly represented in this study and any inferences about the general Si biology of these groups are not possible without further representation in the analysis.

Fig. 3.

Mean (± s.e.m.) relative shoot Si concentration of seven groups of plants (one-way ANOVA, F_6,728 = 18·11, P < 0·001, residual mean square = 1·053). Silicon concentrations in leaf or non-woody shoot tissues of 735 plant species were obtained from 125 independent studies reported in 54 papers in the primary literature. Standard errors of differences of means (s.e.d.) between groups can be calculated as √{residual mean square * [(1/n₁) + (1/n₂)]}. Groups are ranked from lowest to highest mean relative shoot Si concentration: ferns (n = 59), gymnosperms (67), angiosperms (600), mosses (1), clubmosses (5), horse-tails (2), liverworts (1).

Relative shoot Si concentrations were, in general, low in angiosperms, gymnosperms and ferns. However, there was substantial variation in shoot Si concentration within these well-represented groups. The 59 species of ferns sampled in this study were assigned to 14 families representing seven orders (Table 1). The relative shoot Si concentration of ferns ranged from −2·139 in Colysis wrightii (Polypodiaceae) to 1·352 in Athyrium filix-femina (Woodsiaceae). Although there were no significant differences in mean relative shoot Si concentration between fern orders (one-way ANOVA, F_6,52 = 1·29, P > 0·05, r.m.s. = 2·448), there were differences in the mean relative shoot Si concentration between the seven fern families sampled from the best-represented fern order (Aspleniales; one-way ANOVA, F_6,36 = 4·27, P < 0·01, r.m.s. = 2·729). There were notable differences in relative shoot Si concentration between species in the Woodsiaceae (0·59, n = 11) and in the Dryopteridaceae (–1·68, n = 19).

The 67 species of gymnosperms sampled in this study were assigned to nine families representing five orders (Table 1). The relative shoot Si concentration of gymnosperms ranged from −0·078 in Ephedra sinica (Ephedraceae) to 4·512 in Abies pectinata (Pinaceae). There were no significant differences in mean relative shoot Si concentration between gymnosperm orders (one-way ANOVA, F_4,62 = 0·46, P > 0·05, r.m.s. = 0·387). Further, there were no significant differences in the mean relative shoot Si concentration between the five gymnosperm families sampled from the best-represented gymnosperm order (Pinales; one-way ANOVA, F_4,56 = 0·01, P > 0·05, r.m.s. = 0·428). In the three well-represented families from this order, mean relative shoot Si concentrations were 0·333 (Taxodiaceae, n = 6), 0·379 (Cupressaceae, n = 10) and 0·387 (Pinaceae, n = 43).

The 600 species of angiosperms sampled in this study were assigned to 114 families of plants representing 44 orders/families unassigned to order (Table 1). These comprised 34 non-monocot and ten monocot (five commelinoid and five non-commelinoid) clades. Mean relative shoot Si concentrations differed significantly between these 44 clades (one-way ANOVA, F_43,556 = 5·17, P < 0·001, r.m.s. = 0·76; Fig. 4). Within non-monocot angiosperms, notable low relative shoot Si concentrations occurred amongst Brassicales (0·010, n = 9), Aquifoliales (0·102, n = 3), Cornales (0·196, n = 4) and Fabales (0·263, n = 36) species. High relative shoot Si concentrations were observed in species of Saxifragales (1·351, n = 5), with notable Si accumulation in two species of Crassulaceae (Rhodiola linearifolia, 2·679; Sedum hybridum, 3·329). High relative shoot Si concentrations were also observed in several species of Fagales (0·786, n = 25) including Fagus sylvatica (6·089) and Quercus spp. from the Fagaceae family, in the Rosales (0·764, n = 25) including species from the Celtidaceae, Elaeagnaceae, Ulmaceae and Urticaceae families, in the Asterales (e.g. Helianthus spp.), and in the Caryophyllales (Polygonum spp.). There was intermediate-to-high relative shoot Si concentration in the basal angiosperm groups, although these groups were poorly represented in the analysis (Magnoliales 0·578, n = 4; Laurales 0·592, n = 4; Piperales 0·617, n = 2; Nymphaeaceae 0·685, n = 1; Schisandraceae 1·209, n = 1).

Fig. 4.

Mean (±s.e.m.) relative shoot Si concentration in 44 angiosperm clades (representing orders or unassigned families; one-way ANOVA, F_43,556 = 5·17, P < 0·001, residual mean square = 0·76). Data were obtained from 125 independent studies in 54 papers in the primary literature. Standard errors of differences of means (s.e.d.) between clades can be calculated as √{residual mean square * [(1/n₁) + (1/n₂)]}. Groups are ranked from lowest to highest mean relative shoot Si concentration: Acorales (n = 2), Brassicales (9), Liliales (3), Asparagales (24), Aquifoliales (3), Santalales (1), Pandanales (1), Celastraceae (1), Cornales (4), Bromeliaceae (2), Geraniales (1), Vitaceae (1), Fabales (31), Commelinales (1), Myrtales (10), Garryales (1), Malpighiales (13), Solanales (11), Ericales (26), Staphyleaceae (1), Sapindales (13), Gentianales (8), Zingiberales (4), Proteales (1), Ranunculales (10), Cucurbitales (4), Apiales (10), Lamiales (28), Malvales (8), Magnoliales (4), Laurales (4), Caryophyllales (42), Piperales (2), Dipsacales (2), Alismatales (9), Asterales (48), Nymphaeaceae (1), Rosales (25), Fagales (25), Boraginaceae (2), Arecales (9), Schisandraceae (1), Saxifragales (5), Poales (189). Mean shoot Si concentration of Acorales and Brassicales is –0·028 and 0·010, respectively.

Within monocots, shoot Si concentration was substantially lower in non-commelinoid monocot species than in commelinoid monocots (Fig. 5). Indeed, three of the four angiosperm orders containing the lowest shoot Si concentrations were the non-commelinoid monocot orders Acorales (–0·028, n = 2), Liliales (0·055, n = 3) and Asparagales (0·081, n = 24). In contrast, the well-replicated commelinoid monocot orders Arecales (1·204, n = 9) and Poales (1·554, n = 189) had consistently high relative shoot Si concentrations. The few species sampled from other commelinoid monocot clades had low relative shoot Si concentrations, similar to species in non-commelinoid monocot clades, e.g. species of Bromeliaceae (0·199, n = 2) and Commelinales (0·292, n = 1). Thus, from the available data in the published literature, it is concluded that high shoot Si concentration is not a general feature of monocots.

Fig. 5.

Percentage frequency distribution of mean relative shoot Si concentration of 600 species of angiosperms classified into commelinoid monocot (continuous line), non-commelinoid monocot (dashed line), or non-monocot (dotted line) groupings.

The main products of Si accumulation are the phytoliths, or silica bodies, which infill the cell walls and lumina of certain cells in plant tissues (Prychid et al., 2004). The shapes and sizes of these phytoliths contain considerable taxonomic information (Powers, 1992; Prychid et al., 2004) and are increasingly being used in both palaeoecological (e.g. Parker et al., 2004) and archaeological (e.g. Ishida et al., 2003) research, since they provide useful information on past vegetation, agriculture and food. Notably, Prychid et al. (2004), working on phytolith systematics in monocots, suggested that silica accumulation was confined to the commelinoid monocots, with the single exception of the Orchidaceae. Since Piperno (1988, tables 2.2–2.4) found that phytolith production was closely related to plant Si content, the observation of Prychid et al. (2004) is consistent with this analysis of published shoot Si data, subject to the caveat that only two Orchidaceae species were represented in the present data set. Thus, this analysis of published shoot Si data indicates which phylogenetic groups are most likely to contain species that are good phytolith producers. Further, this analysis also indicates that shoot Si content, and thus phytolith production, will be influenced more by the higher-level phylogenetic position of a plant rather than by environmental effects such as water availability, temperature, and Si availability in the soil, although environmental effects will influence phytolith production under some circumstances (e.g. Rosen and Weiner, 1994).

In addition to providing useful potential palaeoecological and archaeological information, knowledge of phylogenetic variation in shoot Si accumulation may also inform studies of the biogeochemical cycling of Si, and those of the molecular genetics of Si uptake and transport in plants. For example, Carnelli et al. (2001) estimated the annual contribution of alpine plant communities to the Si biogeochemical cycle in alpine environments and, unsurprisingly, observed that grasslands were the greatest silica producers. Relative Si production in other plant communities could be estimated by multiplying the mean relative shoot Si concentration of each plant phylogenetic grouping represented (e.g. plant family), by the percentage abundance for each group.

To date, Si transporters have only been located in diatoms (Hildebrand et al., 1997). However, rice (a heavy Si accumulator with a mean relative shoot Si concentration of 4·167) has recently become a model plant for the study of Si uptake and transport in vascular plants (Ma et al., 2002, 2004; Mitani and Ma, 2005). Since a rice mutant with markedly decreased Si uptake compared with its wild type has recently been identified (Ma et al., 2002), it seems likely that Si transporter(s) in higher plants will be isolated in due course. The present data will facilitate comparative functional genetic analysis of these transporters (e.g. Mitani and Ma, 2005), by allowing closely related target species with contrasting Si accumulation patterns to be identified for gene/trait association analysis.

There are many phylogenetic groups of plant species that are not represented in this study. To remedy this, further field surveys or comparative experiments are needed and potential sampling strategies are described in Broadley et al. (2003). In the case of Si, field surveys are likely to yield more appropriate information than laboratory experiments for two reasons. First, it has been shown that relative shoot Ca and Mg data are broadly consistent between experimental and field conditions (Broadley et al., 2003, 2004). Since plant-available soil Si is likely to vary less than plant-available soil Ca and Mg between sites, and since there is a relatively small effect of site on relative shoot Si concentration, it is a reasonable (and testable) assumption that field data will correspond in relative terms to comparative experimental data. The second reason is that it is easier and cheaper to sample large numbers of species from their natural habitats—or from botanical collections—than to grow them experimentally from seeds or cuttings. Once further data are collected, it will be possible (1) to determine precisely where Si accumulation traits diverge within commelinoid monocots, (2) to test which of the non-vascular plant groups are characterized by high Si accumulation, and (3) to identify if distinct ordinal/family-level Si accumulation traits occur in groups of species not currently represented in the present data set.

SUPPLEMENTARY INFORMATION

Online at http://aob.oxfordjournals.org provides raw shoot/leaf Si concentrations on a dry weight basis of 735 plant species sampled from 125 studies, contained in 54 papers in the primary literature (full references in the Appendix), in which Si concentrations of leaf or non-woody shoot tissue were reported.

APPENDIX

This Appendix provides data sources for meta-analysis to calculate mean relative shoot Si concentration in plants. Study numbers, in square brackets, are cited in Table 1 and in Supplementary Information.

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