Hormone-metabolic interactions in adventitious roots (Invited Review)
Annals of Botany 123: 929–950, 2019
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Adventitious rooting has an important ecological role and is critical for propagation of many crops. Druege et al. integrate new findings on the hormonal and metabolic interactions on adventitious root formation in cuttings. Considering the genetic and epigenetic control and the environment at stock plant and cutting level, molecular factors controlling phytohormone and metabolic homeostasis and signalling are highlighted. Pinpointing light, nitrogen and iron as crucial environmental factors, the authors provide a system-oriented concept of adventitious rooting. Druege et al. emphasize the need and the perspectives for functional analysis of underlying molecular processes and of the functional equilibrium of the whole system.
Authors: Uwe Druege, Alexander Hilo, José Manuel Pérez-Pérez, Yvonne Klopotek, Manuel Acosta, Fahimeh Shahinnia, Siegfried Zerche, Philipp Franken, and Mohammad R. Hajirezaei
The role of pollinator preference to maintain pollen colour variation
Annals of Botany 122: 951–960, 2019
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Pollinators often drive the evolution of floral traits, but their capacity to influence the evolution of pollen colour remains unclear. Ison et al. examined whether pollinators can contribute to the maintenance of the white to purple pollen colour variation in Campanula americana (Campanulaceae). The specialist bee, Megachile campanulae (Hymenoptera), displayed a strong preference for purple-pollen plants, but also removed twice as much pollen per visit when compared to other pollinators. Ilson et al. suggest that Megachile’s pollen colour preference is resulting in the prevalence of white pollen in eastern populations of C. americana and is thus helping to maintain pollen colour variation throughout the range.
Authors: Jennifer L. Ison, Elizabeth S.L. Tuan, Matthew H. Koski, Jack S. Whalen, and Laura F. Galloway
For a Commentary on this article see this issue, pp. iv–vi.
WALTer: A 3D wheat model that simulates tillering dynamics
Annals of Botany 123: 961–976, 2019
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Lecarpentier et al. developed a three dimensional model for the growth and development of wheat plants from sowing to heading. The individual-based model integrates plant response to light via the modification of the number of ears produced per plant. That is defined according to a local Green Area Index (GAI) nearby the plant and by the quantity of incoming radiations intercepted by each tiller. WALTer’s behaviour was evaluated by cross validation on experimental data. It is the first model to predict with accuracy known behaviour of wheat plants, using only simple rules: a plant produces fewer tillers in dense canopies.
Authors: Christophe Lecarpentier, Romain Barillot, Emmanuelle Blanc, Mariem Abichou, Isabelle Goldringer, Pierre Barbillon, Jérôme Enjalbert, and Bruno Andrieu
Candidate gene identification in perennial ryegrass
Annals of Botany 123: 977–992, 2019
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Perennial ryegrass (Lolium perenne, Poaceae) is a widely grown forage and amenity grass for which there are considerable and varied, but often under-exploited, genetic resources. To explore their potential, Harper et al. developed a BAC-based physical map of the perennial ryegrass genome and integrated this with a genome-wide association study across a perennial ryegrass European ecotype collection. They identify a number of genomic regions associated with traits such as flowering time and water soluble carbohydrate accumulation. In the future, the physical map can be integrated with whole genome sequencing efforts to improve genome assemblies for perennial ryegrass.
Authors: J. Harper, J. De Vega, S. Swain, D. Heavens, D. Gasior, A. Thomas, C. Evans, A. Lovatt, S. Lister, D. Thorogood, L. Skøt, M. Hegarty, T. Blackmore, D. Kudrna, S. Byrne, T. Asp, W. Powell, N. Fernandez-Fuentes, and I. Armstead
Peach shoot types and the control of vegetative growth in trees
Annals of Botany 123: 993–1004, 2019
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In peach (Prunus persica, Rosaceae) trees, different shoots can be distinguished depending on the time of their appearance and origin. Proleptic shoots are partially pre-formed in a bud and grow after dormancy. Sylleptic shoots are neo-formed and grow in axils of leaves as the parent shoot grows. Prats-Llinàs et al. show that the number of phytomers and bud fate patterns of the two types of shoots are similar even though proleptic shoots started to grow earlier in the season than sylleptic shoots. Thus, the structure of both types of shoots with similar length appears to be under similar genetic control. This research provides insights into how trees are constructed, an avenue for phenotypic characterization of tree architecture, and a scientific foundation for vegetative management (pruning) of fruit trees.
Authors: Maria Teresa Prats-Llinàs, Gerardo López, Katherine Fyhrie, Benoît Pallas, Yann Guédon, Evelyne Costes, and Theodore M. DeJong
Multidirectional evolution of floral chemistry in deceptive Dactylorhiza orchids
Annals of Botany 123: 1005–1016, 2019
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Floral chemistry is hypothesized to be the product of natural selection, but researchers have just begun to consider the micro-evolution of these traits. Wróblewska et al. studied floral chemical signals in deceptive Dactylorhiza orchids that might have evolved through the action of two mechanisms. First, the floral chemical compounds (e.g., aldehydes and n-alkanes/alkenes), which are considered to be pheromones, and which relay information about food, attract similar pollinators to each taxon. Second, the domination of single chemical groups in the different taxa (e.g., benzoids and acids) enrich the plant-insect chemical communication. The complex genetic evolution of floral chemical compounds influences the sexual, social and feeding behaviour of pollinators and results in attracting both shared and species-specific pollinators.
Authors: Ada Wróblewska, Lech Szczepaniak, Andrzej Bajguz, Iwona Jędrzejczyk, Izabela Tałałaj, Beata Ostrowiecka, Emilia Brzosko, Edyta Jermakowicz, and Paweł Mirski
Mechanisms of reproductive interference in Taraxacum
Annals of Botany 123: 1017–1028, 2019
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Reproductive interference can reduce fitness of either of the involved species, and its ecological and evolutionary consequences may depend on its underlying mechanisms. Takemori et al. investigated three different mechanisms of reproductive interference from an alien to a native Taraxacum (Asteraceae) species, pollinator preference, heterospecific pollen deposition, and hybridization, and evaluate their relative importance. Heterospecific pollen deposition, especially when the alien pollen is applied before conspecific pollen, may have the largest deleterious effect. The effect of heterospecific pollen deposition is frequency dependent; thus, it may cause a positive-feedback loop that increases the effect on the population dynamics over time.
Authors: Akane Takemori, Akiyo Naiki, Ko-Ichi Takakura, Masahiro M. Kanaoka, and Sachiko Nishida.
Larger apples have lower natural defences against pests
Annals of Botany 123: 1029–1042, 2019
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The ancestor of the modern apple produced small bitter fruits about the size of cherries. These were transformed by domestication into the large sweet fruits we enjoy today. Whitehead and Poveda investigate whether selection for large fruits unintentionally reduced the resources that trees have to invest in another key function—the production of phytochemicals that provide natural protection against pests. Their results show a clear trade-off between fruit size and phytochemical production, helping to explain why our modern varieties are highly susceptible to diseases and pests. This new understanding of yield-defence trade-offs has broad implications for improving the sustainability of fruit production.
Authors: Susan R. Whitehead and Katja Poveda
Fruit heteromorphism and naturalization success in Asteraceae
Annals of Botany 122: 1043–1052, 2019
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Finding the factors that explain invasion success of species is a major objective in ecology. The combination of extensive data on fruit heteromorphism in Asteraceae and the largest global plant-naturalization database offered the unprecedented possibility to add a missing piece to the naturalization-success puzzle. Fenesi et al. show for the first time that fruit heteromorphism correlates with naturalization success. However, they also show that this correlation most likely reflects a successful combination of other biological traits in fruit heteromorphic species. This emphasizes the importance of compiling and analysing multivariate datasets when testing how naturalization success relates to species characteristics.
Authors: Annamária Fenesi, Dorottya Sándor, Petr Pyšek, Wayne Dawson, Eszter Ruprecht, Franz Essl, Holger Kreft, Jan Pergl, Patrick Weigelt, Marten Winter, and Mark van Kleunen
Genes involved in the biosynthesis of Chiloglottis semiochemicals
Annals of Botany 122: 1053–1066, 2019
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Selection on duplicated plant volatile genes is thought to have enabled the evolution of floral volatiles crucial to plant-insect interactions. Wong et al. explore the expression and evolution of fatty acid pathway genes implicated in the biosynthesis of chiloglottone semiochemicals employed by Australian sexually deceptive Chiloglottis orchids. Comparative transcriptome analysis revealed that fatty acid pathways are upregulated in chiloglottone-producing tissues. Phylogenetic and selection analysis indicated that the differentially expressed β-ketoacyl synthase I duplicate (KASI-2B) experienced relaxed purifying selection in Chiloglottis. Wong et al. conclude that Chiloglottis KASI-2B may hold the key to the biosynthesis of chiloglottones.
Authors: Darren C. J. Wong, Ranamalie Amarasinghe, Vasiliki Falara, Eran Pichersky, and Rod Peakall
Reproductive assurance weakens pollinator-mediated selection on flower size
Annals of Botany 122: 1067–1078, 2019
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The consequences of delayed selfing by reproductive assurance for selection on flower size in mixed-mating species is relevant to understand the evolution of plant breeding systems. In the Mediterranean annual Tuberaria guttata (Cistaceae), Teixido and Aizen estimate pollinator- and selfing-mediated selection on flower size in three populations contrasting in pollination environment. Reproductive assurance decreased with flower size in all populations and intensely increased seed production in the least-visited population, counteracting pollinator-mediated selection for larger corollas. Their study suggests that the balance between the extent of reproductive assurance and outcrossing contributes to determine flower size in mixed-mating systems, which ultimately depends on pollinator availability.
Authors: Alberto L. Teixido and Marcelo A. Aizen
Red:far-red photoreceptors in maize determine plant growth and grain yield
Annals of Botany 122: 1079–1088, 2019
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Phytochrome B is a photoreceptor that controls plant plasticity and resource partitioning. Little is known about its impact on maize crops. Wies et al. tested maize plants deficient in this photoreceptor, in the field at two contrasting plant densities. At the higher density, deficient plants grew at a similar rate to controls but at the lower density, they were smaller and yielded less than controls. This indicates that active phytochromes B in high-available-light canopies (low density) inhibit shade avoidance responses and allow plants to express their potential for growth and yield. These observations highlight the potential of phyB locus as a breeding target to improve crop growth.
Authors: Germán Wies, Anita Ida Mantese, Jorge José Casal, and Gustavo Ángel Maddonni
Relationships between Tertiary relict and circumboreal woodland floras
Annals of Botany 122: 1089–1098, 2019
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Two major categories of Northern Hemisphere intercontinental disjunctions are Tertiary relict disjunctions and Arctic/circumboreal distributions. Little attention has been given to links or transitions between them. Liu et al. present a biogeographic study, based on a plant group Chimaphila within Ericaceae family. Their results show a close link between Tertiary relict and circumboreal biota, and reveal that the circumboreal woodland biome has an older origin than most true arctic–alpine taxa, having gradually recruited taxa since the early Oligocene. It is not clear in which direction Pyroloideae lineages moved between Tertiary relict disjunctions and Arctic/circumboreal distributions and each biome might have recruited species from the other.
Authors: Zhen-Wen Liu, Jing Zhou, Hua Peng, John V. Freudenstein, and Richard I. Milne
