Consequences of Local Conspecific Density Effects for Plant Diversity and Community Dynamics.

Conspecific density dependence (CDD) in plant populations is widespread, most likely caused by local-scale biotic interactions, and has potentially important implications for biodiversity, community composition, and ecosystem processes. However, progress in this important area of ecology has been hindered by differing viewpoints on CDD across subfields in ecology, lack of synthesis across CDD-related frameworks, and misunderstandings about how empirical measurements of local CDD fit within the context of broader ecological theories on community assembly and diversity maintenance. Here, we propose a conceptual synthesis of local-scale CDD and its causes, including species-specific antagonistic and mutualistic interactions. First, we compare and clarify different uses of CDD and related concepts across subfields within ecology. We suggest the use of local stabilizing/destabilizing CDD to refer to the scenario where local conspecific density effects are more negative/positive than heterospecific effects. Second, we discuss different mechanisms for local stabilizing and destabilizing CDD, how those mechanisms are interrelated, and how they cut across several fields of study within ecology. Third, we place local stabilizing/destabilizing CDD within the context of broader ecological theories and discuss implications and challenges related to scaling up the effects of local CDD on populations, communities, and metacommunities. The ultimate goal of this synthesis is to provide a conceptual roadmap for researchers studying local CDD and its implications for population and community dynamics.

Coexistence of Competing Plants Under Plant-Soil Feedback.

Plant-soil feedback (PSF), the reciprocal interaction between plants and their soil environment, is a fundamental ecological process that can influence coexistence and functional structure in plant communities. Current theory establishes that PSF may enhance diversity or lead to exclusion depending on whether soil conditioning disproportionately benefits heterospecific or conspecific individuals. However, a more complete picture of the impact of PSF requires understanding how PSF interacts with competition. To that end, here we propose an integrated mathematical model combining trait-based competition and soil-explicit PSF. Contrary to the current paradigm, we find that soil conditioning that disproportionately favours conspecific individuals can promote coexistence. Additionally, we show that priority effects are common when soil-conditioning species differ in their edaphic preferences. These effects can allow species with large differences in competitive ability to coexist under certain soil conditions. Our results provide testable predictions tying community-level functional patterns in plant communities to PSF and competition.

How Climate Change May Impact Plant Reproduction and Fitness by Altering the Temporal Separation of Male and Female Flowering.

The temporal separation of male and female flowering-known as dichogamy-is a widespread adaptation across the plant kingdom that increases reproductive success and enhances plant fitness. Differences in timing between male and female flowering can be highly sensitive to environmental variation-and with widespread evidence of shifts in seasonal timing of flowering (i.e., phenology) due to anthropogenic warming-climate change may alter the sequences of male and female flowering for a diversity of taxa around the globe. However, we currently lack a broad understanding of both the extent to which climate change may alter patterns of dichogamy and the potential implications of these shifts for plant reproduction. Here I present evidence that links variation in dichogamy to variation in temperature for a variety of plant taxa. I synthesize the limited number of studies that have investigated shifts in dichogamy specifically in the context of climate change, and detail the physiological, genetic, and developmental factors that control the relative timing of male and female flowering. The literature indicates that dichogamy is highly plastic and sensitive to temperature variation. Plasticity in dichogamy is observed across species with different sexual systems and growth habits, and in both female-first and male-first flowering taxa, but at present, no clear patterns of dichogamy shifts related to these associated traits are discernible. Together, these lines of evidence suggest that sequences of male and female flowering are likely to shift with climate change. However, more research is needed to better understand and predict the ecological consequences of shifting patterns of dichogamy in the context of global change.

Long-Term Alpine Plant Responses to Global Change Drivers Depend on Functional Traits.

Forecasting plant responses under global change is a critical but challenging endeavour. Despite seemingly idiosyncratic responses of species to global change, greater generalisation of 'winners' and 'losers' may emerge from considering how species functional traits influence responses and how these responses scale to the community level. Here, we synthesised six long-term global change experiments combined with locally measured functional traits. We quantified the change in abundance and probability of establishment through time for 70 alpine plant species and then assessed if leaf and stature traits were predictive of species and community responses across nitrogen addition, snow addition and warming treatments. Overall, we found that plants with more resource-acquisitive trait strategies increased in abundance but each global change factor was related to different functional strategies. Nitrogen addition favoured species with lower leaf nitrogen, snow addition favoured species with cheaply constructed leaves and warming showed few consistent trends. Community-weighted mean changes in trait values in response to nitrogen addition, snow addition and warming were often different from species-specific trait effects on abundance and establishment, reflecting in part the responses and traits of dominant species. Together, these results highlight that the effects of traits can differ by scale and response of interest.

The physiology of plants in the context of space exploration.

The stress that the space environment can induce on plant physiology is of both abiotic and biotic nature. The abiotic space environment is characterized by ionizing radiation and altered gravity, geomagnetic field (GMF), pressure, and light conditions. Biotic interactions include both pathogenic and beneficial interactions. Here, we provide an overall picture of the effects of abiotic and biotic space-related factors on plant physiology. The knowledge required for the success of future space missions will lead to a better understanding of fundamental aspects of plant physiological responses, thus providing useful tools for plant breeding and agricultural practices on Earth.

The biomechanics of turgor pressure.

If you ever forget to water your houseplant, you may find its leaves getting soft and droopy - if you water it again in time, the leaves may stiffen, spring back up, and resist gravity. During this recovery, plant cells absorb water and build up an intracellular pressure, called turgor pressure, similar to inflating a balloon. Turgor pressure is an intrinsic component of plant physiology, and its biomechanical role as the 'hydroskeleton' is generally appreciated either statically in structural stability, like leaves resisting gravity, or dynamically in rapid motions, like Venus flytrap snapping, Mimosa closing, or stomatal opening. Slow but non-static processes like plant cell expansion also rely on turgor pressure, and it has been increasingly realized that turgor pressure and water fluxes in plant tissues play active roles in plant growth and morphogenesis. But where does turgor pressure come from, and how does it interact with other biomechanical properties of a plant cell? This primer aims to answer these questions by taking a brief tour from osmosis, to pressure vessel theory, then plant cell rheology. Although this primer is centered around intracellular pressure in plant cells, the biomechanical concepts are generally applicable to other organisms like bacteria and fungi, and even animal cells, which do not have cell walls, but are either embedded in stiff extracellular matrix (ECM) or are contracting (see the following section). To explain some of these concepts, we included a few equations, most of which are not hard to derive at all. We encourage readers to check the included examples, try for themselves, and look up derivations in suggested further reading materials.

Microballistics in fungi and plants.

Ballistic movements in biology are powered by muscle contraction, explosive chemical reactions, the formation and collapse of gas bubbles, merger of fluid droplets, and release of hydrostatic pressure. At the macroscopic end of this kinetic carnival we find jumping fleas, violent spider jaws, shrimp claw hammers, and squirting beetles and cucumbers. The speeds are startling, but the mechanisms seem familiar because they occur on a spatial scale that overlaps with our physical experiences. We jump, albeit more slowly than fleas, for example, and it does not seem strange that seeds will spurt from a swollen cucumber when it hits the ground. Ballistics in microscopic dimensions are very different, operating in a seemingly alien world of fluid mechanics where thin air becomes soup and gravity vanishes.

Curvature in plants.

Curvatures are ubiquitous in the animal kingdom - the spiral shell of the nautilus and the corkscrew horns of the blackbuck being iconic examples. Dynamic changes in curvature (i.e., curving) are most striking in the locomotion of some animal species - swimming in fishes and mollusks, looping in leeches, undulatory locomotion in snakes and lampreys, and also sperm motility through flagellum beating. When it comes to plants, which are sessile organisms with a rigid body, the terms 'curvature' and 'curving' evoke very different images - leaves of grass swaying in the breeze, a trunk dangerously bent by a powerful gust of wind, a branch sagging under the weight of its own fruits, as well as the frail arabesques of twining plants like the morning glory and the ivy, which were so influential in the Art Nouveau movement and many other artistic traditions. These various vegetal curves not only prompt creative inspiration in the mind of the beholder, they also initiate signaling cascades leading to developmental responses of the plant. Conversely, curvature can result from a biologically active process in response to an internal or external stimulus. Active curving or decurving are indeed important aspects of the plastic interplay of the developmental program of plants and their environment. Although easily accessible to observation, curvature and curving have only recently become the focus of active research in plant development. Lying at the nexus of biology, physics and mathematics, they require an interdisciplinary approach. The aim of this primer is to give readers an intuitive but accurate understanding of what curvature and curving are, as observed in the plant kingdom, then a more formal definition. We will discuss their role in plant development, both as a signal and as a response, and finally the practical issues and solutions involved in measuring plant curvatures.

Exploring the complex information processes underlying plant behavior.

Newly discovered plant behaviors, linked to historical observations, contemporary technologies, and emerging knowledge of signaling mechanisms, argue that plants utilize complex information processing systems. Plants are goal-oriented in an evolutionary and physiological sense; they demonstrate agency and learning. While most studies on plant plasticity, learning, and memory deal with the responsiveness of individual plants to resource availability and biotic stresses, adaptive information is often perceived from and coordinated with neighboring plants, while competition occurs for limited resources. Based on existing knowledge, technologies, and sustainability principles, climate-smart agricultural practices are now being adopted to enhance crop resilience and productivity. A deeper understanding of the dynamics of plant behavior offers a rich palette of potential amelioration strategies for improving the productivity and health of natural and agricultural ecosystems.

Silicate-based mineral materials promote submerged plant growth: Insights from plant physiology and microbiomes.

Restoring submerged plants naturally has been a significant challenge in water ecology restoration programs. Some silicate-based mineral materials have shown promise in improving the substrate properties for plant growth. While it is well-established that silicate mineral materials enhance submerged plant growth by improving salt release and reducing salt stress, the influence of rhizosphere microorganisms on phytohormone synthesis and key enzyme activities has been underestimated. This study focused on two typical silicate mineral materials, bentonite and maifanite, to investigate their effects on Myriophyllum oguraense from both plant physiology and microbiome perspectives. The results demonstrated that both bentonite and maifanite regulated the synthesis of phytohormones such as gibberellin (GA) and methyl salicylate (MESA), leading to inhibition of cellular senescence and promotion of cell division. Moreover, these silicate mineral materials enhanced the activity of antioxidant enzymes, thereby reducing intracellular reactive oxygen species levels. They also optimized the structure of rhizosphere microbial communities, increasing the proportion of functional microorganisms like Nitrospirota and Sva0485, which indirectly influenced plant metabolism. Analysis of sediment physicochemical properties revealed increased rare earth elements, macronutrients, and oxygen content in pore water in the presence of silicate materials, creating favorable conditions for root growth. Overall, these findings shed light on the multifaceted mechanisms by which natural silicate mineral materials promote the growth of aquatic plants, offering a promising solution for restoring aquatic vegetation in eutrophic lake sediments.

Exogenous Substances Used to Relieve Plants from Drought Stress and Their Associated Underlying Mechanisms.

Drought stress (DS) is one of the abiotic stresses that plants encounter commonly in nature, which affects their life, reduces agricultural output, and prevents crops from growing in certain areas. To enhance plant tolerance against DS, abundant exogenous substances (ESs) have been attempted and proven to be effective in helping plants relieve DS. Understanding the effect of each ES on alleviation of plant DS and mechanisms involved in the DS relieving process has become a research focus and hotspot that has drawn much attention in the field of botany, agronomy, and ecology. With an extensive and comprehensive review and summary of hundred publications, this paper groups various ESs based on their individual effects on alleviating plant/crop DS with details of the underlying mechanisms involved in the DS-relieving process of: (1) synthesizing more osmotic adjustment substances; (2) improving antioxidant pathways; (3) promoting photosynthesis; (4) improving plant nutritional status; and (5) regulating phytohormones. Moreover, a detailed discussion and perspective are given in terms of how to meet the challenges imposed by erratic and severe droughts in the agrosystem through using promising and effective ESs in the right way and at the right time.

An Integrated Framework for Drought Stress in Plants.

With global warming, drought stress is becoming increasingly severe, causing serious impacts on crop yield and quality. In order to survive under adverse conditions such as drought stress, plants have evolved a certain mechanism to cope. The tolerance to drought stress is mainly improved through the synergistic effect of regulatory pathways, such as transcription factors, phytohormone, stomatal movement, osmotic substances, sRNA, and antioxidant systems. This study summarizes the research progress on plant drought resistance, in order to provide a reference for improving plant drought resistance and cultivating drought-resistant varieties through genetic engineering technology.

Molecular Mechanisms Underlying Freezing Tolerance in Plants: Implications for Cryopreservation.

Cryopreservation is a crucial technique for the long-term ex situ conservation of plant genetic resources, particularly in the context of global biodiversity decline. This process entails freezing biological material at ultra-low temperatures using liquid nitrogen, which effectively halts metabolic activities and preserves plant tissues over extended periods. Over the past seven decades, a plethora of techniques for cryopreserving plant materials have been developed. These include slow freezing, vitrification, encapsulation dehydration, encapsulation-vitrification, droplet vitrification, cryo-plates, and cryo-mesh techniques. A key challenge in the advancement of cryopreservation lies in our ability to understand the molecular processes underlying plant freezing tolerance. These mechanisms include cold acclimatization, the activation of cold-responsive genes through pathways such as the ICE-CBF-COR cascade, and the protective roles of transcription factors, non-coding RNAs, and epigenetic modifications. Furthermore, specialized proteins, such as antifreeze proteins (AFPs) and late embryogenesis abundant (LEA) proteins, play crucial roles in protecting plant cells during freezing and thawing. Despite its potential, cryopreservation faces significant challenges, particularly in standardizing protocols for a wide range of plant species, especially those from tropical and subtropical regions. This review highlights the importance of ongoing research and the integration of omics technologies to improve cryopreservation techniques, ensuring their effectiveness across diverse plant species and contributing to global efforts regarding biodiversity conservation.

Global patterns of plant functional traits and their relationships to climate.

Plant functional traits (FTs) determine growth, reproduction and survival strategies of plants adapted to their growth environment. Exploring global geographic patterns of FTs, their covariation and their relationships to climate are necessary steps towards better-founded predictions of how global environmental change will affect ecosystem composition. We compile an extensive global dataset for 16 FTs and characterise trait-trait and trait-climate relationships separately within non-woody, woody deciduous and woody evergreen plant groups, using multivariate analysis and generalised additive models (GAMs). Among the six major FTs considered, two dominant trait dimensions-representing plant size and the leaf economics spectrum (LES) respectively-are identified within all three groups. Size traits (plant height, diaspore mass) however are generally higher in warmer climates, while LES traits (leaf mass and nitrogen per area) are higher in drier climates. Larger leaves are associated principally with warmer winters in woody evergreens, but with wetter climates in non-woody plants. GAM-simulated global patterns for all 16 FTs explain up to three-quarters of global trait variation. Global maps obtained by upscaling GAMs are broadly in agreement with iNaturalist citizen-science FT data. This analysis contributes to the foundations for global trait-based ecosystem modelling by demonstrating universal relationships between FTs and climate.

Naturalized species drive functional trait shifts in plant communities.

Despite decades of research documenting the consequences of naturalized and invasive plant species on ecosystem functions, our understanding of the functional underpinnings of these changes remains rudimentary. This is partially due to ineffective scaling of trait differences between native and naturalized species to whole plant communities. Working with data from over 75,000 plots and over 5,500 species from across the United States, we show that changes in the functional composition of communities associated with increasing abundance of naturalized species mirror the differences in traits between native and naturalized plants. We find that communities with greater abundance of naturalized species are more resource acquisitive aboveground and belowground, shorter, more shallowly rooted, and increasingly aligned with an independent strategy for belowground resource acquisition via thin fine roots with high specific root length. We observe shifts toward herbaceous-dominated communities but shifts within both woody and herbaceous functional groups follow community-level patterns for most traits. Patterns are remarkably similar across desert, grassland, and forest ecosystems. Our results demonstrate that the establishment and spread of naturalized species, likely in combination with underlying environmental shifts, leads to predictable and consistent changes in community-level traits that can alter ecosystem functions.

Weak link or strong foundation? Vulnerability of fine root networks and stems to xylem embolism.

Resolving the position of roots in the whole-plant hierarchy of drought-induced xylem embolism resistance is fundamental for predicting when species become isolated from soil water resources. Published research generally suggests that roots are the most vulnerable organ of the plant vascular system, although estimates vary significantly. However, our knowledge of root embolism excludes the fine roots (< 2 mm diameter) that form the bulk of total absorptive surface area of the root network for water and nutrient uptake. We measured fine root and stem xylem vulnerability in 10 vascular plant species from the major land plant clades (five angiosperms, three conifers, a fern and lycophyte), using standardised in situ methods (Optical Methods and MicroCT). Mean fine root embolism resistance across the network matched or exceeded stems in all study species. In six of these species (one fern, one lycophyte, three conifers and one angiosperm), fine roots were significantly more embolism resistant than stems. No clear relationship was found between root xylem conduit diameter and vulnerability. These results provide insight into the resistance of the plant hydraulic pathway at the site of water and nutrient uptake, and challenge the long-standing assumption that fine roots are more vulnerable than stems.

Emerging roles of the C-to-U RNA editing in plant stress responses.

RNA editing is an important post-transcriptional event in all living cells. Within chloroplasts and mitochondria of higher plants, RNA editing involves the deamination of specific cytosine (C) residues in precursor RNAs to uracil (U). An increasing number of recent studies detail specificity of C-to-U RNA editing as an essential prerequisite for several plant stress-related responses. In this review, we summarize the current understanding of responses and functions of C-to-U RNA editing in plants under various stress conditions to provide theoretical reference for future research.