Annals of botany最新文献

Background and aims: Trees are increasingly at risk of maladaptation to their environment as climates change rapidly worldwide. Although adaptive evolution through natural selection is a key mechanism by which populations and species can persist in changing environments, we have limited information regarding the phenotypic traits under selection in warm and dry environments. We answer the following research questions: (1) What ecophysiological traits are under selection in warm, dry environments? (2) Does intrapopulation trait integration affect the response to selection in the warmer, drier site? (3) Is the plastic response of traits under selection adaptive?

Methods: Using Picea mariana (black spruce) as a case study, we studied 425 trees representing seven provenances across three 50-year-old common garden trials established along a spatial climate gradient across eastern Canada. We measured height growth rate as a performance metric, and 10 traits that reflect water use, thermoregulation, structural support, and photosynthetic rate.

Results: All traits were under selection in at least one site, mostly in combination with other traits. For two trait combinations, the strength of selection gradients significantly increased from the colder, wetter site to the warmer, drier site: water use efficiency (WUE) with Huber value (HV), and carbon-to-nitrogen ratio (CN) with HV. In the warmer and drier site, trait-trait correlations among these three traits were largely absent, except for CN:HV in two provenances. Overall, reaction norms suggest that the plastic response was not aligned with selection for trait pairs in warm, dry climates.

Conclusions: Results suggest that adaptive evolution in response to climate change in P. mariana may favor phenotypes with fewer needles that are conservative for water and resource use. In the seven study provenances, intrapopulation trait integration should minimally impede adaptive evolution, but plastic responses to warmer and drier conditions may constrain the expression of optimally adapted phenotypes.

Background and aims: Fibonacci spiral phyllotaxis is overwhelmingly the most common leaf arrangement among plants, both today and in the fossil record. Spiral phyllotaxis appeared as early as the Late Devonian, some 380 million years ago. This mathematical property has been rigorously studied in living conifer species; however, the phyllotaxis of fossil conifer seed cones remains under-studied, including that of the Middle Jurassic seed cones of Araucaria mirabilis.

Methods: Twenty-one A. mirabilis seed cones from the Bosques Petrificados de Jaramillo National Park, Argentina, were analyzed for their morphometrics, phyllotaxis, and seediness. For each cone, the number of seeds in the cone, as well as the number of clockwise and counterclockwise parastichies, was counted on the well-preserved cone surface. Micro-CT was used to non-destructively observe the internal arrangement of the seeds in the cone. Then, Avizo was used to visualize one clockwise and one counterclockwise parastichy from each cone to determine the number of seeds in the spiral and the angle of rotation of the spiral.

Key results: Here, we show that clockwise ontogenetic chirality and greater axis length and width positively correlate to greater seediness in A. mirabilis seed cones. Cones with clockwise ontogenetic chirality have moderately tighter spirals (p-value < 0.05, r = 0.2) with more seeds in them (p-value < 0.05, r = 0.3). Similarly, a taller axis is associated with a greater circumference (p-value < 0.01, r = 0.6), which, in turn, correlates with more bract/scale complexes (p-value < 0.05, r = 0.05). The most common phyllotaxis is 13,21 (64%) with 360° spirals (48%) and clockwise ontogenetic chirality (66%).

Conclusions: Visualizing internal morphometrics and seed arrangements show which characteristics contribute to optimal seed packing. Thus, micro-CT imaging, in addition to traditional methods, enables a deeper study of conifer cone morphology and construction.

Background and aims: The Lateral Organ Boundaries Domain (LBD) transcription factors play a significant role in root development and abiotic stress in plants. In a previous study, the LBD family gene ThLBD11 was cloned and characterized from Tamarix hispida, being positioned at the second layer of the salt stress gene regulatory network (GRN) in T. hispida. Suggesting that ThLBD11 may play a role in the salt stress process.

Methods: We investigated the salt tolerance function and regulatory mechanisms of ThLBD11 using multiple sequence alignment, phylogenetic tree analysis, biochemical staining, physiological indicators, yeast one-hybrid (Y1H), Electrophoretic Mobility Shift Assay (EMSA), GUS histochemical analysis, GO enrichment analysis, Chromatin immunoprecipitation assay (ChIP) and RT-qPCR.

Key results: In this study, the ThLBD11 was overexpressed in T. hispida. Under salt stress, the OE lines exhibited elevated antioxidant enzyme activity, reduced cellular damage and regulated ion homeostasis. The Y1H, EMSA and GUS histochemical analysis results showed that ThLBD11 was able to specifically bind to CGGC cis-element. By integrating GO enrichment analysis and promoter CGGC element counts, two downstream target genes (ThAHL27, ThATPD) of ThLBD11 in the GRN were confirmed. The RT-qPCR and ChIP-PCR results indicated that ThLBD11 negatively regulated the expression of ThAHL27 and ThATPD by directly binding to their promoter fragments containing the CGGC motif.

Conclusions: ThLBD11 acts as a positive regulator of salt stress tolerance in T. hispida by inhibiting the expression of ThAHL27 and ThATPD. These findings contribute to the understanding of the regulatory mechanism of salt stress adaptation in T. hispida.

Background and aims: Crop growth models (CGM) are a valuable tool for predicting crop performance in contrasting growing conditions and interpreting crop responses to future scenarios. Inaccuracies in the simulation of leaf area dynamics directly impact estimates of intercepted radiation, biomass production and transpiration demand by the crop, especially during the early stages when the canopy is not yet fully covering the soil. An empirical bell-shaped function of individual leaf area versus leaf position, combined with the response of leaf appearance to thermal time, is used in many CGMs to simulate total leaf area per axis and generate canopy leaf area index. This study proposes that an individual leaf area approach, based on predicting blade length and blade width of successive leaves, can make modelling of leaf area dynamics less empirical, while offering the flexibility to better simulate genotypic, and genotypic × environment interaction effects in sorghum (Sorghum bicolor (L.) Moench), maize (Zea mays L.), and pearl millet (Pennisteum americanum L.).

Methods: A generic model of leaf area by leaf position was developed using data on individual blade length and width compiled from numerous experiments over the period 1990-2022 that involved a broad range of genotypes of sorghum, maize, and pearl millet.

Key results: This study developed and tested a generic individual leaf size model for maize, sorghum and pearl millet, based on relationships quantifying length and width of successive leaves. Generic parameters of an expolinear-logistic model obtained across species and related to total leaf number (TLN) as appropriate, facilitated satisfactory predictive performance for blade length, width, and leaf area profiles. Genotypic-specific parameters improved model predictions in this study.

Conclusions: Improvements in parameterisation of canopy development in CGM can enhance predictions of Genotype × Environment × Management (G×E×M) interactions to support identifying breeding targets for enhanced yield and strategies for sustainable crop management.

Background and aims: Dry dehiscent fruits have independently evolved multiple times during angiosperm diversification. A striking example is the convergent evolution of Brassicaceae siliques and Papaveraceae pods, both formed by two fused carpels forming valves that meet at a replum or replum-like structure. In both cases, valve separation occurs through a dehiscence zone at the valve margins in contact with the replum. In Arabidopsis, fruit development is regulated by transcription factors: FRUITFULL (FUL) ensures proper valve cell division, REPLUMLESS (RPL) specifies replum identity and SHATTERPROOF (SHP1/2) genes pattern the dehiscence zone. SHP1/2 also regulate INDEHISCENT (IND) for lignified layer formation and ALCATRAZ (ALC) and SPATULA (SPT) for the non-lignified layer. The network is downregulated by APETALA2 (AP2), which influences replum formation and valve margin growth.

Methods: Using previously published and new in situ RNA hybridization expression data, we evaluated how this network applies to basal eudicots.

Key results: In Bocconia frutescens, homologue expression suggests conserved roles for FUL and AP2 in fruit wall proliferation, acting antagonistically to ALC and RPL homologues localized to the dehiscence zone. A role for STK homologues in dehiscence zone formation cannot be excluded, while a role of AG-like genes, the closest homologues of SHP during fruit development, is unlikely.

Conclusions: Our findings indicate significant rewiring of the fruit developmental network between basal and core eudicots, underscoring the need for functional studies in non-eudicot species to validate this framework.

Background and aims: Throughout leaf development, cell expansion is dynamic and driven by the balance between local cell wall mechanical properties and the intracellular turgor pressure that overcomes the stiffness of the cell wall leading to plastic deformation. The epidermal pavement cells in most leaves begin development as small, polygonally shaped cells, but in mature leaves epidermal pavement cells are often shaped as highly lobed puzzle pieces. However, the developmental and biomechanical trajectories between these two end points have not before been fully characterized.

Methods: We characterized how epidermal pavement cell size and shape, cell wall thickness and hydraulic traits change during leaf expansion in the tropical understorey fern Microsorum grossum (Polypodiaceae).

Key results: As fronds expanded by approximately two orders of magnitude in size, epidermal pavement cells became increasingly lobed as cell walls thickened. Furthermore, the timing of these developmental changes varied across the lamina, starting first near the frond base and midrib, followed by more apical and lateral regions. During expansion, fronds also underwent substantial physiological changes: as cells expanded and cell walls thickened, intracellular turgor pressure and the bulk cell wall modulus of elasticity both increased while the water potential at turgor loss and the minimum epidermal conductance to water vapour both decreased.

Conclusions: These results highlight the dynamic coordination between anatomical and physiological traits throughout leaf development, provide valuable data for biophysical modelling of leaf development, and highlight the vulnerability of developing leaves to drought conditions.

Background and aims: Successional theory predicts directional shifts in plant community composition following disturbance. However, the long-term effects of chronic, recurring disturbances on plant ecological strategies at the community level in human-altered landscapes, and how they differ between the assemblages of native and alien species, remain poorly understood.

Methods: Using Grime's competitor, stress-tolerator, ruderal (CSR) framework, we examine temporal and spatial changes in plant strategies at the community level in the Three Gorges Reservoir Area, China. Based on repeated plant community surveys in 2012 and 2018 at the same localities, we assess the differences in the assemblages of native and alien strategies in response to chronic disturbances by extreme hydrological fluctuations and intense human activities over time and along a shoreline-to-upland disturbance gradient.

Key results: Our results reveal a temporal shift in native assemblages, with a decline in R-score and an increase in C- and S-scores, while alien assemblages maintained a strong R-strategy. Spatial patterns show that native assemblages adopted a mid-elevation peak in C-strategy, with S- and R-strategies dominating at higher and lower elevations, respectively. In contrast, there is no spatial variation in the CSR strategies of alien plant assemblages.

Conclusions: Our findings demonstrate that chronic disturbances (e.g. water fluctuations and human activities) drive a spatiotemporal decoupling of the CSR strategies between native and alien plant assemblages. This divergence requires targeted management by prioritizing suppression of ruderal alien species and promoting competitive and stress-tolerant native species to guide succession dynamics.

Background and aims: Intraspecific trait variations in response to nutrient availability are expected to depend on (1) the category of traits considered, and (2) species ecology, with species requiring high nutrient levels expected to be more plastic. However, there are few comparisons of trait responses considering simultaneously (a) above-ground traits approximating ecological strategies, (b) root traits involved in nutrient acquisition, and (c) traits integrating the whole plant, and including multiple species.

Methods: We studied 17 annual species coming from two contrasted environments in the same rangeland of southern France. Plants were grown in a common garden under two fertilization treatments.

Key results: We evidenced no effect of origin on trait values, suggesting little or no differentiation according to the environment of origin. Among the 14 traits measured, whole-plant traits, in particular plant nitrogen content, plant dry mass and root mass fraction, showed strong plastic responses to fertilization, whereas the response was weak or even absent for above- and below-ground organ-level traits related to ecological strategies, suggesting that they play a secondary role in plant responses to nutrient availability. Finally, species' ecological preferences (i.e. their nutrient requirements), predicted the plasticity in plant nitrogen content per mass, whereas species position along the acquisition-conservation trade-off (approximated by leaf traits) predicted plasticity in plant dry mass. This cautions against the systematic use of leaf traits as a proxy of species ecology and functioning.

Conclusions: Our results challenge the assumption that leaf traits universally reflect plant responses to nutrient availability. They advocate a better characterization of traits directly involved in nutrient acquisition and underscore the importance of considering how trait-trait and trait-environment relationships may depend on the group of species considered. These findings offer an avenue for more accurate predictions of plant responses to nutrient gradients in natural and managed ecosystems.