ContentSnapshots

A framework for understanding silicon’s role in plant biology (Review)

Annals of Botany 121: 1265–1273, 2018

doi: 10.1093/aob/mcy009

The beneficial effects of silicon (Si), a neglected plant nutrient, have received substantial recognition in recent years. Despite recent advances, most research has focused on the effects of Si application on the alleviation of a biotic or abiotic stress, yet the underlying mechanisms remain undefined. There is mounting evidence suggesting a fundamental role for Si in plant primary metabolism. Frew et al. highlight gaps in the understanding of the role of Si in plant biology, and propose a more holistic research framework of how this challenge could be addressed.

Authors: Adam Frew, Leslie A. Weston, Olivia L. Reynolds, and Geoff M. Gurr

Canadian fossil provides an Early Cretaceous age for the moss family Grimmiaceae

Annals of Botany 121: 1275–1286, 2018

doi: 10.1093/aob/mcy015

Compared to vascular plants, mosses have a much sparser fossil record, especially in pre-Cenozoic rocks (more than 70 million years old). Savoretti et al. discovered an Early Cretaceous (Valanginian) fossil on Vancouver Island, Canada. Using high-resolution serial sectioning, they find that it represented a new moss genus and species, Tricarinella crassiphylla. Despite minute size, the fossil contains anatomical information supporting placement in the moss family Grimmiaceae, thus providing the oldest record for the family and a minimum age of 136 million years. This discovery highlights the importance of anatomically preserved plant fossils for documenting past biodiversity, bolstering ongoing efforts aimed at identifying additional bryophyte fossils.

Authors: Adolfina Savoretti, Alexander C. Bippus, Ruth A. Stockey, Gar W. Rothwell, and Alexandru M. F. Tomescu

Effects of cold treatments on apomixis

Annals of Botany 121: 1287–1298, 2018

doi: 10.1093/aob/mcy017

The natural triggers for shifts to apomixis (asexual reproduction via seed) are still not well understood. Klatt et al. test the hypothesis that low temperature can induce apomixis in the alpine species Ranunculus kuepferi (Ranuculaceae). They analyse phenology, seed set and mode of seed formation of diploid and tetraploid plants under controlled cold/warm treatments. Cold treatments reduced sexual seed set in both cytotypes, and increased frequencies of apomictic seed formation in warm-adapted diploids, but not in cold-adapted tetraploids. Expression of apomixis may be a consequence of cold-induced disturbances of the sexual pathway, but not necessarily dependent on polyploidy.

Authors: Simone Klatt, Christoph C. F. Schinkel, Bernhard Kirchheimer, Stefan Dullinger, and Elvira Hörandl

Splash dispersal and disease resistance in mixtures of cultivars with contrasting height

Annals of Botany 121: 1299–1308, 2018

doi: 10.1093/aob/mcy024

Cultivar mixtures have an important role to play in reducing the propagation of diseases, as is evident from the well-documented results of growing mixtures of cultivars from plants that exhibit different levels of susceptibility to certain pathogens. Vidal et al. assess the impact of plant height of wheat (Triticum aestivum) in cultivar mixtures exposed to splash dispersal of Zymoseptoria tritici causing septoria tritici leaf blotch. A modelling approach is used with an explicit description of canopy architecture and splash dispersal processes in three dimensions. The results suggest that differences in plant height within mixtures can enhance disease reduction through mixture effects, such as barrier, height and umbrella effects, on spore dispersal.

Authors: T. Vidal, C. Gigot, C. de Vallavieille-Pope, L. Huber, and S. Saint-Jean

A reassessment of the genome size – invasiveness relationship in reed canary grass

Annals of Botany 121: 1309–1318, 2018

doi: 10.1093/aob/mcy028

Smaller genomes have been linked to increased invasiveness in plants. Key evidence comes from Phalaris arundinacea (Poaceae), where previous work reported faster growth rates of individuals with smaller genomes, and smaller genomes in the invasive versus native range. Martinez et al. re-investigate these claims and are unable to substantiate them using best-practice genome size estimation protocols. They conclude that differential invasiveness in this species is not driven by genome size variation, and that appropriate genome size estimation methods are critical.

Authors: Megan A. Martinez, Eric J. Baack, Stephen M. Hovick, and Kenneth D. Whitney

Why are the seed cones of conifers so diverse at pollination?

Annals of Botany 121: 1319–1331, 2018

doi: 10.1093/aob/mcy029

The evolution of reproductive diversity in wind-pollinated plants is not well understood. In conifers, which are all wind pollinated, Losada and Leslie use anatomical sections to show that different rates of cone development can generate a wide range of morphological diversity at pollination, even though all cones perform the same basic function. Wind tunnel analyses using these cones suggest that different morphologies are equally effective in capturing pollen, demonstrating how simple differences in development can give rise to equally functional morphologies. Such processes may underlie reproductive diversification across wind-pollinated plants more broadly.

Authors: Juan M. Losada and Andrew B. Leslie

CAM recycling and salt tolerance in Talinumtriangulare

Annals of Botany 121: 1333–1342, 2018

doi: 10.1093/aob/mcy030

Talinum triangulare (waterleaf, Talinaceae) is a perennial terrestrial pantropical herb in which crassulacean acid metabolism (CAM) is induced by drought. Montero et al. examine whether salinity can induce CAM in this species. Plants were irrigated with solutions of increasing NaCl concentration. They tolerated treatment with NaCl up to 300 mM, while treatment with 400 mM NaCl decreased photosynthetic rate, growth and reproductive effort. Under 300 mM NaCl, plants had a significantly higher nocturnal acid accumulation than the control plants, and showed no nocturnal CO₂ uptake indicative of the operation of CAM. This is the first report of CAM induction by salt in Talinum triangulare that can be classified as a halo-tolerant species.

Authors: Estefanía Montero, Ana Marta Francisco, Enrique Montes, and Ana Herrera

Contrasting effects of yeast and bacteria on floral nectar traits

Annals of Botany 121: 1343–1349, 2018

doi: 10.1093/aob/mcy032

Individual flowers vary in rewards they provide to pollinators, but what are the causes of this variation? Vannette and Fukami examine how yeasts and bacteria that commonly inhabit floral nectar, influence flower characteristics including nectar composition and longevity. They inoculated flowers of the plant Mimulus aurantiacus (sticky monkeyflower, Phrymaceae) with yeasts, bacteria, or sugar, and measured flower traits. Although both microbial species grew well in nectar, yeasts decreased amino acid concentration, while bacteria tended to increase amino acid concentration, but reduced sugar concentration and nectar volume. Vannette and Fukami conclude that different types of microbes increase variation in nectar characteristics and availability among flowers, with potential consequences for pollination.

Authors: Rachel L. Vannette and Tadashi Fukami

Altitudinal differentiation in water-repellency of bud-wrapping leaves

Annals of Botany 121: 1351–1360, 2018

doi: 10.1093/aob/mcy033

In rosette-forming plants, rosette leaves locate near the ground and their upper surfaces are exposed, whereas the opposite surfaces are more exposed for leaves on flowering stems. Aryal et al. investigate water-repellency of leaves of Arabidopsis halleri subsp. gemmifera (Brassicaceae) growing in contrasting montane habitats along an altitudinal gradient at Mt Ibuki, Japan. Bud-wrapping leaves on flowering stems are highly water-repellent for the plants from high altitude compared with those for the plants in low altitude, presumably to protect flowering buds from frost damage. The difference is shown to have a genetic base, and involves a key gene, AhgCER1, that controls leaf-surface wax.

Authors: Biva Aryal, Wataru Shinohara, Mie N. Honjo, and Hiroshi Kudoh

Abscisic acid affects rice cell wall phosphate remobilization and P transporation

Annals of Botany 121: 1361–1368, 2018

doi: 10.1093/aob/mcy034

Zhu et al. use cultivated rice (Oryza sativa, ‘Nipponbare’) to study the effect of abscisic acid (ABA) on the cell wall inorganic phosphate (Pi) remobilization under phosphorus (P)-deficient condition. They find that nitric oxide (NO) levels increase as quickly as the decrement of ABA levels. This inhibits both the ABA-induced reduction of pectin content for the reutilization of cell wall P and the ABA-induced down-regulation of OsPT6 for the translocation of P from roots to shoots. Thus, the growth of rice under P-deficient conditions is improved. Furthermore, this ABA-regulated cell wall P reutilization may be relatively independent of the NO–ethylene pathway, and further study in this area would be beneficial.

Authors: Xiao Fang Zhu, Xu Sheng Zha, Qi Wu, and Ren Fang Shen

Functional drought response in the Brachypodiumdistachyon species complex

Annals of Botany 121: 1369–1382, 2018

doi: 10.1093/aob/mcy037

Although numerous studies have investigated the phenotypic consequences of allopolyploidy (hybridization and whole-genome duplication), conclusive evidence for the novel and transgressive performance of allopolyploids remains elusive. Martínez et al. analyse the drought-response in the Brachypodium distachyon species complex, a model for functional genomics of temperate cereals. They find that as part of drought-response, leaf phytohormone concentration, of B. hybridum allotetraploids is transgressive compared to their diploid species ancestors, B. distachyon and B. stacei. Given the importance of phytohormones in regulating drought stress, the higher levels of phytohormones in B. hybridum allotetraploids under drought may contribute to their successful persistence in drier environments.

Authors: Luisa M. Martínez, Ana Fernández-Ocaña, Pedro J. Rey, Teresa Salido, Francisco Amil-Ruiz, and Antonio J. Manzaneda

Non-structural carbohydrate dynamics in shrubland under drought-induced die-off

Annals of Botany 121: 1383–1396, 2018

doi: 10.1093/aob/mcy039

Drought-induced canopy loss in Mediterranean woody plants alters non-structural carbohydrate (NSC) dynamics. Lloret et al. find that climatic drought leads to leaf loss and reduced NSC concentrations in stems and roots that do not recover after seasonal rainfall in a shrubland community in the Ebro valley of Spain. In contrast, and consistent with their critical metabolic functions, soluble sugars (SS) decreased only slightly, and increased with foliage recovery after rainfall. Among-species variability in NSC dynamics is related to wood density, with stronger NSC reduction and higher SS concentrations with leaf loss during drought in low relative to high wood density species of a shrubland community in the Ebro valley of Spain.

Authors: Francisco Lloret, Gerard Sapes, Teresa Rosas, Lucía Galiano, Sandra Saura-Mas, Anna Sala, and Jordi Martínez-Vilalta

Modelling polycyclic growth and leaf neoformation in trees

Annals of Botany 121: 1397–1410, 2018

doi: 10.1093/aob/mcy040

Trees can adapt their architecture in response to climate change by adjusting growth processes such as leaf neoformation and polycyclic growth. Tondjo et al. present work aimed to improve the plant growth model GreenLab in order to take into consideration these processes through stochastic functions. The model is tested using existing data collected on planted teak trees (Tectona grandis, Lamiaceae) in Togo, Africa. Simulations reproduced the observed tree architectures and biomass production at different ages satisfactorily. The main advantage of Greenlab is its mathematical formulation that allows direct and fast calculation of a single tree or a forest.

Authors: Kodjo Tondjo, Loïc Brancheriau, Sylvie Sabatier, Adzo Dzifa Kokutse, Kouami Kokou, Marc Jaeger, Philippe De Reffye, and Thierry Fourcaud

Floral morphogenesis in Camptotheca

Annals of Botany 121: 1411–1425, 2018

doi: 10.1093/aob/mcy041

Inflorescence and floral development of Camptotheca acuminata (Nyssaceae) were studied with a scanning electron microscope and stereo microscope. Gong et al. describe the plant’s architecture as constituting a botyroid with floral units (FUs), with each FU capitate with dyads instead of flowers. Each flower has five toothed calyx lobes, five petals and ten stamens. The ovary is syncarpous and unilocular. The ovule is unitegmic and heterotropous. Inflorescences are functionally andromonoecious varying with the position of the FUs on the inflorescence system. The investigation complements and supports findings from molecular systematic studies.

Authors: Jing-zhi Gong, Qiu-jie Li, Xi Wang, Yue-ping Ma, Xiao-hui Zhang, Liang Zhao, Zhao-yang Chang, and Louis Ronse De Craene