Plant abiotic stress response and nutrient use efficiency

Abiotic stresses and soil nutrient limitations are major environmental conditions that reduce plant growth, productivity and quality.Plants have evolved mechanisms to perceive these environmental challenges, transmit the stress signals within cells as well as between cells and tissues, and make appropriate adjustments in their growth and development in order to survive and reproduce. In recent years, significant progress has been made on many fronts of the stress signaling research, particularly in understanding the downstream signaling events that culminate at the activation of stress-and nutrient limitation-responsive genes, cellular ion homeostasis, and growth adjustment. However, the revelation of the early events of stress signaling, particularly the identification of primary stress sensors, still lags behind. In this review, we summarize recent work on the genetic and molecular mechanisms of plant abiotic stress and nutrient limitation sensing and signaling and discuss new directions for future studies.     

Interplay between ethylene and nitrogen nutrition: How ethylene orchestrates nitrogen responses in plants

The stress hormone ethylene plays a key role in plant adaptation to adverse environmental conditions.Nitrogen(N) is the most quantitatively required mineral nutrient for plants,and its availability is a major determinant for crop production.Changes in N availability or N forms can alter ethylene biosynthesis and/or signaling.Ethylene serves as an important cellular signal to mediate root system architecture adaptation,N uptake and translocation,ammonium toxicity,anthocyanin accumulation,and prem...     

Signals Regulating Multiple Responses to Wounding and Herbivores

Damage inflicted by herbivore feeding necessitates multiple defense strategies in plants. The wound site must be sealed and defense responses mounted against the herbivore itself and against invading opportunistic pathogens. These defenses are controlled both in time and space by highly complex regulatory networks that themselves are modulated by interactions with other signaling pathways. In this review, we describe the signaling events that occur in individual wounded leaves, in systemic unwounded regions of the plant, and between the plant, and other organisms, and attempt to place these events in the context of a coordinated system. Key signals that are discussed include ion fluxes, active oxygen species, protein phosphorylation cascades, the plant hormones jasmonic acid, ethylene, abscisic acid and salicylic acid, peptide signals, glycans, volatile chemicals, and physical signals such as hydraulic and electrical signals. Themes that emerge after consideration of the published data are that glycans and peptide elicitors are likely primary triggers of wound-induced defense responses and that they function through the action of jasmonic acid, a central mediator of defense gene expression, whose effect is modulated by ethylene. In the field, wound signaling pathways are significantly impacted on by other stress response pathways, including pathogen responses that often operate through potentially antagonistic signals such as salicylic acid. However, gross generalisations are not possible because some wound and pathogen responses operate through common jasmonate- and ethylene-dependent pathways. Understanding the ways in which local and systemic wound signaling pathways are coordinated individually and in the context of the plants wider environment is a key challenge in the application of this science to crop-protection strategies.     

植物抗旱性中的补偿效应及其在农业节水中的应用

在论述植物补偿效应存在类型和研究范畴的基础上,详细评述了植物抗旱性中根系形态结构功能及地上部干物质积累、产量和水分利用效率方面的补偿效应及其影响因素,并对植物抗旱作用中补偿生长的可能生理学机制作了探讨。同时,对补偿效应在提高农业水分利用效率中的应用进行了讨论     

Chemical root to shoot signaling under drought

Chemical signals are important for plant adaptation to water stress. As soils become dry, root-sourced signals are transported via the xylem to leaves and result in reduced water loss and decreased leaf growth. The presence of chemical signals in xylem sap is accepted, but the identity of these signals is controversial. Abscisic acid (ABA), pH, cytokinins, a precursor of ethylene, malate and other unidentified factors have all been implicated in root to shoot signaling under drought. This review describes current knowledge of, and advances in, research on chemical signals that are sent from roots under drought. The contribution of these different potential signals is discussed within the context of their role in stress signaling.     

Electrical signals in avocado trees: Responses to light and water availability conditions

Plant responses to environmental changes are associated with electrical excitability and signaling; automatic and continuous measurements of electrical potential differences (ΔEP) between plant tissues can be effectively used to study information transport mechanisms and physiological responses that result from external stimuli on plants. The generation and conduction of electrochemical impulses within plant different tissues and organs, resulting from abiotic and biotic changes in environmental conditions is reported. In this work, electrical potential differences are monitored continuously using Ag/AgCl microelectrodes, inserted 5 mm deep into sapwood at two positions in the trunks of several Avocado trees. Electrodes are referenced to a non polarisable Ag/AgCl microelectrode installed 20 cm deep in the soil. Systematic patterns of ΔEP during absolute darkness, day-night cycles and different conditions of soil water availability are discussed as alternative tools to assess early plant stress conditions.Key words: plant electrical potential, light and dark cycles, water availability, plant signaling, avocado trees, plant sensors, irrigation automation     

Reactive oxygen species signaling and stomatal movement in plant responses to drought stress and pathogen attack

Stomata, the pores formed by a pair of guard cells, are the main gateways for water transpiration and photosynthetic CO_2 exchange, as well as pathogen invasion in land plants. Guard cell movement is regulated by a combination of environmental factors, including water status, light, CO_2 levels and pathogen attack, as well as endogenous signals, such as abscisic acid and apoplastic reactive oxygen species(ROS). Under abiotic and bioticstress conditions, extracellular ROS are mainly produced by plasma membrane-localized NADPH oxidases, whereas intracellular ROS are produced in multiple organelles. These ROS form a sophisticated cellular signaling network, with the accumulation of apoplastic ROS an early hallmark of stomatal movement. Here, we review recent progress in understanding the molecular mechanisms of the ROS signaling network,primarily during drought stress and pathogen attack. We summarize the roles of apoplastic ROS in regulating stomatal movement, ABA and CO_2 signaling, and immunity responses.Finally, we discuss ROS accumulation and communication between organelles and cells. This information provides a conceptual framework for understanding how ROS signaling is integrated with various signaling pathways during plant responses to abiotic and biotic stress stimuli.     

Root-targeted biotechnology to mediate hormonal signalling and improve crop stress tolerance

Since plant root systems capture both water and nutrients essential for the formation of crop yield, there has been renewed biotechnological focus on root system improvement. Although water and nutrient uptake can be facilitated by membrane proteins known as aquaporins and nutrient transporters, respectively, there is a little evidence that root-localised overexpression of these proteins improves plant growth or stress tolerance. Recent work suggests that the major classes of phytohormones are involved not only in regulating aquaporin and nutrient transporter expression and activity, but also in sculpting root system architecture. Root-specific expression of plant and bacterial phytohormone-related genes, using either root-specific or root-inducible promoters or grafting non-transformed plants onto constitutive hormone producing rootstocks, has examined the role of root hormone production in mediating crop stress tolerance. Root-specific traits such as root system architecture, sensing of edaphic stress and root-to-shoot communication can be exploited to improve resource (water and nutrients) capture and plant development under resource-limited conditions. Thus, root system engineering provides new opportunities to maintain sustainable crop production under changing environmental conditions.     

The stomata frontline of plant interaction with the environment-perspectives from hormone regulation

Plants have evolved elaborate mechanisms to perceive and integrate signals from various environmental conditions.On leaf surface,stomata formed by pairs of guard cells mediate gas exchange,water transp...     

高等植物对环境胁迫的适应与其胁迫信号的转导

高等植物适应环境胁迫有多种水平与尺度的生理与生化方式,但其本质却是分子水平的基因时空表达与调控,它又受到胁迫信号转导途径的多重调控与影响。环境胁迫的主要形式是冷害、干旱、盐碱胁迫与UV-B辐射等,而它们又是影响高等植物生长、发育、繁殖等重要过程的生态因子,同时也是作物高效生产必需重视的因素,对其与植物相互作用的分子机理的认识有重要理论意义与实践意义。从细胞与组织和器官水平获得的分子生物学规律,只有应用到个体,群体,及生态系统中才会更有生命力。如何将这些数据资料成为宝贵的永续资源是21世纪植物系统生物学面临的主要挑战之一。主要从农业生态环境角度阐述环境胁迫信号转导的分子生物学作用方式,新进展资料的整合并建立起它们的可能联系及本领域中存在的相关问题和可能的解决途径,为高效的农业生态可持续发展提供分子生物学方面的理论基础。     

Understanding osmotic stress tolerance in leaves and nodules of two <Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> cultivars with contrasting drought tolerance

Drought and salinity are environmental constraints that affect crop yields worldwide. In nature, both stresses are multifaceted problems that are usually associated with other adverse circumstances which limit plant performance such as water shortage and nutrient deficits. In order to assess common features of both stresses, the effects of mannitol-induced osmotic stress were monitored using two Phaseolus vulgaris cultivars, Cv. ‘Flamingo’ (tolerant) and Cv. ‘Coco Blanc’ (sensitive) which differed in their drought and salinity tolerance. Growth, water relations, organic and inorganic compound accumulation and soluble protein contents were measured in leaves and nodules of these N₂-fixing plants. The aim of the present study was to check whether osmotic stress tolerance is associated with accumulation of some of these compounds either in leaves, nodules or both organs. At the whole-plant level, Cv. ‘Flamingo’ showed a better maintenance of plant biomass and shoot water status. At the cell level, this was related to a better osmotic adjustment ability both in leaves and nodules and also to a better adjustment of the cell wall elasticity. At the metabolic level, the contrasting accumulation of the different amino acids in nodules of each cultivar suggested that amino acids pathways can be regulated to different degrees under stress conditions. At the metabolic level, it seems that symbiosis in the sink organ (the nodule) plays a crucial role in conferring drought and salinity tolerance in the common bean.     

The Art of Being Flexible: How to Escape from Shade,Salt, and Drought

Environmental stresses, such as shading of the shoot, drought, and soil salinity, threaten plant growth, yield, and survival. Plants can alleviate the impact of these stresses through various modes of phenotypic plasticity, such as shade avoidance and halotropism. Here, we review the current state of knowledge regarding the mechanisms that control plant developmental responses to shade, salt, and drought stress. We discuss plant hormones and cellular signaling pathways that control shoot branching and elongation responses to shade and root architecture modulation in response to drought and salinity. Because belowground stresses also result in aboveground changes and vice versa, we then outline how a wider palette of plant phenotypic traits is affected by the individual stresses. Consequently, we argue for a research agenda that integrates multiple plant organs, responses, and stresses. This will generate the scientific understanding needed for future crop improvement programs aiming at crops that can maintain yields under variable and suboptimal conditions.A fundamental difference between plant and animal development is the plasticity in organ formation after germination. Whereas animals are born with a complete set of organs, a germinating seedling has just one embryonic root and one or two embryonic leaves, the cotyledons. All other organs are formed postembryonically, by the interplay of developmental programs and environmental conditions. So, although each plant has a basic body plan, its final size and shape are largely determined by the specific conditions that the plant experiences, and its growth can be adjusted to suit those conditions. This interplay is crucial in both natural and agricultural settings where plants forage for resources and often avoid/escape from stress.Examples of how plants adjust to environmental conditions include phototropism (Darwin, 1880) to bring the photosynthesizing leaves into well-lit microsites such as canopy gaps and root proliferation toward moisture- or nutrient-rich areas to enhance water uptake and nutrient acquisition (Comas et al., 2013). Examples of stress escape include shoot elongation away from the shade of neighbor plants (shade avoidance; Pierik and de Wit, 2014), escape from submerged conditions to reach the air (Bailey-Serres and Voesenek, 2008), and root growth away from saline soil microsites (halotropism; Galvan-Ampudia et al., 2013). Although some of these responses are termed escape from stress (e.g. shade avoidance), others are considered as attraction to more favorable conditions (e.g. hydrotropism). In the case of directional growth responses, the most unifying way is probably to consider these as responses to gradients of stresses (e.g. salt) or resources (e.g. water).The molecular, biochemical, and physiological pathways that underlie these responses have been intensively researched, and this has provided substantial knowledge on the regulatory mechanisms. However, relatively little research has been devoted to studying these modes of plasticity in combination. For example, dense plantings of crops growing on irrigated soils in arid conditions likely need to deal with drought, soil salinity, and shading by neighbor crops and weeds simultaneously. Above ground, plants use light cues, particularly enrichment of far-red light (FR) through reflection by nearby vegetation, to detect neighboring vegetation and respond with shade avoidance responses (Casal, 2013; Pierik and de Wit, 2014). Below ground, plants can sense neighbors and their abiotic environment through a variety of putative cues. Some of these result from selective changes made to the rhizospheres by root absorption of minerals and water and excretion of organic compounds. Plants respond to these cues in various ways, including growth toward or away from neighbors, nutrient hotspots, water, and more (Fang et al., 2013; Pierik et al., 2013).Importantly, the global crop production chain is anticipating intensification of various abiotic stresses: increased temperatures, progressive salinization of highly water-limited production grounds, and more extreme situations of drought and flood (Tubiello et al., 2007; Bailey-Serres and Voesenek, 2008; Munns and Tester, 2008). At the same time, agricultural productivity must be increased to feed the ever-expanding global population, calling for high-density cropping systems with potentially severe mutual shading among plants. Therefore, it is of great importance to understand how plants respond to high-density and abiotic stress(es) simultaneously.Here, we will review the current molecular and physiological understanding of both shoot developmental plasticity in response to high plant density-derived light signals (shade avoidance) and root developmental plasticity in response to the widely occurring abiotic stresses salt and drought. We will then implement this mechanistic knowledge to generate ideas about (1) how these different modes of plasticity may interact to modulate the known stress response phenotypes and (2) how responses to one stress may affect responses to a second. Addressing these ideas experimentally will generate the knowledge needed to guide crop improvement programs under suboptimal agricultural conditions.     

Phylogenetic and growth form variation in the scaling of nitrogen and phosphorus in the seed plants

Plant biomass and nutrient allocation explicitly links the evolved strategies of plant species to the material and energy cycles of ecosystems. Allocation of nitrogen (N) and phosphorus (P) is of particular interest because N and P play pivotal roles in many aspects of plant biology, and their availability frequently limits plant growth. Here we present a comparative scaling analysis of a global data compilation detailing the N and P contents of leaves, stems, roots, and reproductive structures of 1,287 species in 152 seed plant families. We find that P and N contents (as well as N : P) are generally highly correlated both within and across organs and that differences exist between woody and herbaceous taxa. Between plant organs, the quantitative form of the scaling relationship changes systematically, depending on whether the organs considered are primarily structural (i.e., stems, roots) or metabolically active (i.e., leaves, reproductive structures). While we find significant phylogenetic signals in the data, similar scaling relationships occur in independently evolving plant lineages, which implies that both the contingencies of evolutionary history and some degree of environmental convergence have led to a common set of rules that constrain the partitioning of nutrients among plant organs.     

Physiological roles of plastid terminal oxidase in plant stress responses

The plastid terminal oxidase (PTOX) is a plastoquinol oxidase localized in the plastids of plants. It is able to transfer electrons from plastoquinone (PQ) to molecular oxygen with the formation of water. Recent studies have suggested that PTOX is beneficial for plants under environmental stresses, since it is involved in the synthesis of photoprotective carotenoids and chlororespiration, which could potentially protect the chloroplast electron transport chain (ETC) from over-reduction. The absence of PTOX in plants usually results in photo-bleached variegated leaves and impaired adaptation to environment alteration. Although PTOX level and activity has been found to increase under a wide range of stress conditions, the functions of plant PTOX in stress responses are still disputed now. In this paper, the possible physiological roles of PTOX in plant stress responses are discussed based on the recent progress.     

Increased precipitation modulates the influence of nitrogen and litter inputs on the nutrient resorption proficiency rather than efficiency of <Emphasis Type="Italic">Leymus chinensis</Emphasis>

Resorption of nutrients from senescing organs is an important conservation mechanism that is usually influenced by the supply of soil nutrients and plant growth requirements. Therefore, it is likely that increases in nitrogen (N), precipitation, and litter could lead to changes in nutrient resorption because of changes in nutrients in the soil and accelerated plant growth in response to the alleviation of water limitations in arid and semiarid environments. In the current study, we investigated the effects of water, N, and litter addition on the nutrient resorption efficiency and proficiency of N and phosphorus (P) in leaves and stems of Leymus chinensis in Inner Mongolia, China. Our results showed that N addition significantly decreased the N resorption efficiency in leaves under water addition, and increased P resorption efficiency under ambient precipitation conditions. There was no apparent influence of either litter or water addition on N and P resorption efficiencies. However, N and litter addition significantly altered N and P resorption proficiencies, and these effects were modulated by water availability. Furthermore, changes in resorption proficiencies were mainly associated with alterations in the nutritional status of green organs in response to water, N and litter addition, except for leaf P. Our findings highlight the importance of increased precipitation in modulating the nutrient resorption proficiency of plants under potentially increased nutrient availability in semiarid grasslands. Therefore, global changes in precipitation and N, and corresponding litter changes could result in complex effects on plant nutrient economies and, in turn, could influence the return of nutrients to the soil.     

干热河谷草本植物生物量分配及其对环境因子的响应

以干热河谷6种草本植物为对象,研究了水分、养分、刈割对生物量在根、茎、叶的分配及异速生长关系的影响.结果表明:刈割处理叶生物量质量分数从25.1%显著增加到31.2%,茎生物量质量分数从43.7%显著降低到34.2%;养分添加处理根生物量质量分数从34.0%显著降低到30.8%;水分处理对生物量分配没有显著影响.物种对根、茎、叶生物量分配有显著影响,适应贫瘠土壤的物种将更多生物量分配给叶和根,对茎生物量的分配相对较低.物种与环境因子存在显著的互作效应,表明环境因子对不同物种的生物量分配影响不同.适应贫瘠土壤的物种叶-茎标度指数和异速生长常数大于其他物种,而茎-根标度指数和异速生长常数小于其他物种.养分显著增加了叶-茎和叶-根的异速生长常数,刈割显著降低了茎-根的标度指数,水分处理则没有显著效应.环境因素对器官间异速生长关系的影响存在种间差异.生物量分配的种间差异及其对环境因素的响应特征可能对植物适应环境变化产生重要影响.     

Retrograde signaling and plant stress: plastid signals initiate cellular stress responses

Retrograde signaling coordinates the expression of nuclear genes encoding organellar proteins with the metabolic and developmental state of the organelle. These plastid signals are essential not only for coordinating photosynthetic gene expression in both the nucleus and in the chloroplasts but also for mediating plant stress responses. The chloroplasts therefore act as sensors of environmental changes and complex networks of plastid signals coordinate cellular activities and assist the cell during plant stress responses. Recent work suggests that information from both cytosolic-signaling and plastid-signaling networks must be integrated for the plant cell to respond optimally to environmental stress.