Pollination intensity and paternity (Invited Review)
Annals of Botany 125:1–9, 2020
doi: 10.1093/aob/mcz159
Among-plant variation in siring success plays an important role in natural selection on floral traits. This variation is influenced by two distinct processes, which are rarely studied in unison. Pollinator-mediated interactions influence pollination success, the rate of pollen deposition onto stigmas. Then, in the post-pollination phase, pollen competition may cause realized paternity to differ from patterns of pollen receipt. Christopher et al. explore the interplay between pollination and post-pollination success, and how these processes respond to ecological factors such as pollination intensity. They note that the relative contribution of pollination and post-pollination processes may not be constant, and may vary widely with pollination intensity.
Authors: D. A. Christopher, R. J. Mitchell, and J. D. Karron
Plants are intelligent, here is how (Viewpoint)
Annals of Botany 125:11–28, 2020
doi: 10.1093/aob/mcz155
Plants are intelligent beings whose goal-directed and purposeful responses help improve their probability of survival. Calvo et al. explain the relationship of their intelligence to adaptability. To understand plant intelligence, the requirements for individual variation in intelligence and real-world conditions are outlined. Identifying plants as intelligent is beneficial to a fuller understanding of what a plant actually is and its evolutionary implications, specifically the relevance of intelligent behaviour to our grasp of selection and fitness. Only by appraising all facets of plant intelligence we can redirect fundamental future research in plant decision-making, error perception or anticipation, and in crop breeding.
Authors: P. Calvo, M. Gagliano, G.M. Souza, and A. Trewavas
Temporal patterns of Brassicaceae diversification
Annals of Botany 125:29–47, 2020
doi: 10.1093/aob/mcz123
Whole-genome duplication (WGD) events are considered important driving forces of diversification of plants. Huang et al. study this phenomenon within the Brassicaceae family also known as crucifers or mustards. Polyploidization is playing a major role in the evolution of the more than 4000 species. Diversification patterns were investigated on phylogenetic chronograms and further compared with family-wide data on genome size variation and species richness. Significant diversification rate shifts were detected during the Mio- and Pliocene under cooler and drier conditions, decoupled from preceding WGDs. Rate shifts are not consistently associated with WGD, and Huang et al. propose that WGDs in general serve as a constant pump for continuous and high species diversification.
Authors: Xiao-Chen Huang, Dimitry A. German, and Marcus A. Koch
Deciphering early angiosperm ecology
Annals of Botany 125:49–57, 2020
doi: 10.1093/aob/mcz131
What are the environmental conditions of early angiosperms emergence and radiation? Such a question has long remained controversial because various applied approaches in the past have drawn conflicting images of early angiosperm ecology. Pouteau et al. provide a new perspective on the question by using environmental niche models for 51 species belonging to extant lineages that diverged early during angiosperm evolution (basal angiosperms) and analysing the resulting pattern of niche overlap based on a phylogenetic reconstruction. This approach reveals a strong convergence of extant basal angiosperms towards tropical montane cloud forests (TMCFs), which might reflect a legacy of an ancestral niche.
Authors: Robin Pouteau, Santiago Trueba, and Sandrine Isnard
Hummingbirds levering flowers promote pollination
Annals of Botany 125: 59–65, 2020
doi: 10.1093/aob/mcz134
Many hummingbird-pollinated flowers are pendulous, with the flower hanging downward from a flexible pedicel. Hummingbirds - which prefer to feed from horizontally-facing flowers - lever up the flowers of a columbine, Aquilegia eximia (Ranunculaceae), during feeding, contacting the stigma and anthers during this motion. Using a simple immobilization experiment, LoPresti et al. find that flowers prevented from being levered had a lower chance of successful pollination. Complementing the experiment, videos revealed that hummingbirds contacted the reproductive structures of control flowers at a higher rate than those of immobilized flowers. They discuss floral morphologies in the context of this “lever hypothesis” and want to inspire investigation into this hypothesis in other hummingbird pollinated plants.
Authors: E.F. LoPresti, J. Goidell, J.M. Mola, M.L. Page, C.D. Specht, C. Stuligross, M.G. Weber, N.M. Williams and R. Karban
Seed germination traits shape communities along a hydroperiod gradient
Annals of Botany 125:67–78, 2020
doi: 10.1093/aob/mcz139
Hydroperiod (duration, depth, and frequency of flooding) drives plant community structure and composition in wetlands resulting in distinct zonation patterns. Rosbakh et al. explore the role of seed germination traits in shaping community assembly along a hydroperiod gradient. A distinct, community-specific seed germination niche exists in reeds, mudflats, swamps, shallow- and deep-water communities that reflect their adaptations to decreasing light intensity, temperature fluctuations and oxygen availability along the hydroperiod gradient. These results support the recent argument that the inclusion of seed germination traits into community ecology adds significant insights to community response to the abiotic and biotic environment.
Authors: Sergey Rosbakh, Shyam S. Phartyal, and Peter Poschlod
Adult maize leaf cuticle development
Annals of Botany 125:79–91, 2020
doi: 10.1093/aob/mcz143
It is not well understood how cuticle-function, as a barrier against dehydration, is related to its composition and structure. Bourgault et al. offer new insights into these relationships from analysis of cuticle development in adult maize leaves. Although cuticles of juvenile maize leaves have been extensively investigated, very little is known about the cuticle of adult maize leaves, which dominate the life cycle of this important crop plant. Chemical, ultrastructural and functional analysis of cuticle development in partially expanded adult maize leaves revealed important roles for wax esters and an osmiophilic, likely cutin-rich, layer in protection from dehydration.
Authors: Richard Bourgault, Susanne Matschi, Miguel Vasquez, Pengfei Qiao, Annika Sonntag, Caleb Charlebois, Marc Mohammadi, Michael J. Scanlon, Laurie G. Smith, and Isabel Molina
Slow and steady diversification in Cyatheaceae
Annals of Botany 125:93–103, 2020
doi: 10.1093/aob/mcz145
Clades with steady diversification rates over long time periods play a role in the build-up of biodiversity and help to understand the uneven distribution of species richness across the tree of life. Loiseau et al. study the tree fern family Cyatheaceae and show that their diversification occurred gradually, within limited phenotypic and ecological boundaries, and yet resulted in a remarkable species richness. Cyatheaceae provide a compelling example of tropics as a museum of biodiversity and illustrate that rapid morphological differentiation, key innovations, and niche divergence are not a prerequisite for a clade to thrive for hundreds of millions of years.
Authors: Oriane Loiseau, Anna Weigand, Sarah Noben, Jonathan Rolland, Daniele Silvestro, Michael Kessler, Marcus Lehnert, Nicolas Salamin
Evolutionary history of Pseudotaxus: old lineage, young populations
Annals of Botany 125:105–117, 2020
doi: 10.1093/aob/mcz153
Why did many monotypic gymnosperms in southeast China remain in relict status given their long evolutionary histories and ample opportunities for allopatric speciation? Based on two chloroplast genome regions and 14 low-copy nuclear loci, Kou et al. inferred the evolutionary history of a typical relict conifer Pseudotaxus chienii (Taxaceae) in southeast China by coalescent-based analyses. They find that the extant populations of this species have become established recently (3.68 Ma). Short and incomplete geographical isolation and weak divergent selection are not enough to drive this species to speciate. The findings provide a new perspective for understanding the formation and evolution of the relict gymnosperm flora of China as well as of the Sino-Japanese Flora.
Authors: Yixuan Kou, Li Zhang, Dengmei Fan, Shanmei Cheng, Dezhu Li, Richard G. J. Hodel, and Zhiyong Zhang
For a Commentary on this article see this issue, pp. iv-vi
Auxin redistribution modifies maize root proliferation
Annals of Botany 125:119–130, 2020
doi: 10.1093/aob/mcz154
Plant roots show enhanced proliferation in phosphate (Pi)-rich patches that enable plants to capture the unevenly distributed Pi. Wang et al. reveal the dynamic response pattern of maize roots with a split-root, hydroponics system where maize roots significantly proliferated in heterogeneous Pi-rich media, especially for second order lateral roots, consequently enhancing maize phosphorus acquisition efficiency mediated by auxin polar transport and auxin redistribution. The interaction of heterogeneous Pi with auxin reprogrammes maize root proliferation, enabling efficient Pi acquisition.
Authors: Xin Wang, Jingjing Feng, Philip J. White, Jianbo Shen, and Lingyun Cheng
Mutualistic relationship between mangrove plants and diazotrophs
Annals of Botany 125:131–144, 2020
doi: 10.1093/aob/mcz164
The tidal flats on which mangroves grow tend to have soil depleted in nitrogen because nitrogen-containing litter is washed offshore. How mangrove plants acquire sufficient nitrogen for their vigorous growth under such conditions has long been debated. Inoue et al. show that the rhizosphere of mangrove plants (Rhizophora stylosa, Rhizophoraceae) is characterized by high levels of nitrogen fixation. In the rhizosphere of relatively small and presumably young trees, low root biomass hosts a diazotrophic community most closely resembling the community found in unvegetated mudflats, but as trees grow and develop higher root biomass, that community evolves and recruits plant-growth-promoting bacteria.
Authors: T. Inoue, A. Shimono, Y. Akaji, S. Baba, A. Takenaka, and H.T. Chan
Plant economics spectrum theory holds true within ferns
Annals of Botany 125:145–155, 2020
doi: 10.1093/aob/mcz166
Ferns are worldwide distributed vascular plants but are relatively poorly represented in current framework of resource economics spectrum theory. Lin et al. investigate the coordination among functional traits within and between leaves and fine roots across 12 coexisting fern species in a subtropical forest in China, and explore the influence of these traits on fern decomposition rates. They demonstrate the existence of an acquisition-conservation trade-off axis within ferns and indicate that traits have important ‘afterlife’ effects on fern litter decomposition. The results suggest that the plant economics spectrum theory that is commonly observed across seed plants can be applied to ferns.
Authors: Dunmei Lin, Shufang Yang, Pengpeng Dou, Hongjuan Wang, Fang Wang, Shenhua Qian, Guangrong Yang, Liang Zhao, Yongchuan Yang, and Nicolas Fanin
Seed and fruit lipid diversity in palms
Annals of Botany 125:157–172, 2020
doi: 10.1093/aob/mcz175
The palm family (Arecaceae) has an important socio-economic role worldwide, in particular as a major source of vegetable oils. However, our knowledge of seed and fruit lipid diversity in the family Arecaceae is limited. Guerin et al. characterized the lipid composition of the seeds of 174 species and fruits of 144 species, revealing a high diversity for lipid traits. Seed lipid traits are very relevant to palm chemotaxonomy, and the data suggest that seed unsaturated fatty acids may provide an adaptive advantage in the coldest environments colonized by palms.
Authors: Chloé Guerin, Julien Serret, Rommel Montúfar, Virginie Vaissayre, Aldecinei Bastos-Siqueira, Tristan Durand-Gasselin, James Tregear, Fabienne Morcillo, and Stéphane Dussert
Anaesthetic impairs jasmonate signalling in carnivorous plant
Annals of Botany 125:173–183, 2020
doi: 10.1093/aob/mcz177
Plants do not have nervous systems but are able to generate electrical signals. The electrical signals are important for initiation of plant defence against herbivorous insects as well as for acquiring nutrients for carnivorous plants. Pavlovič et al. show that volatile general anaesthetic diethyl ether inhibited action potentials in the carnivorous plant Venus flytrap (Dionaea muscipula, Droseraceae) and all downstream reactions, including accumulation of jasmonates and expression of jasmonate-responsive genes. Thus, the carnivorous plant is not able to sense the enemy or prey under anaesthesia which is an intriguing parallel to the effects of anaesthetics on animals, including humans.
Authors: Andrej Pavlovič, Michaela Libiaková, Boris Bokor, Jana Jakšová, Ivan Petřík, Ondřej Novák, and František Baluška
Zn speciation in sweetcorn and maize at different stages of kernel maturity
Annals of Botany 125: 185–193, 2020
doi: 10.1093/aob/mcz179
In situ analyses of zinc accumulation and speciation in sweetcorn and maize (Zea mays) kernels at the immature and mature kernel stages using synchrotron-based X-ray absorption spectroscopy by Cheah et al. show that the embryo contributed 28% of the whole kernel Zn while the endosperm contributed 72%. Embryo Zn was 90% Zn-phytate, and endosperm Zn was complexed with an N-containing ligand. Interestingly in maize endosperm, the proportion of Zn as Zn-phytate increased as the kernel matured. This implied that Zn bioavailability is low in maize but sweetcorn is a potential crop for biofortification to address Zn deficiency affecting a third of the global human population.
Authors: Z.X. Cheah, P.M. Kopittke, K.G. Scheckel, M.R. Noerpel and M.J. Bell