Tree drought physiology: critical research questions and strategies for mitigating climate change effects on forests.

Droughts of increasing severity and frequency are a primary cause of forest mortality associated with climate change. Yet, fundamental knowledge gaps regarding the complex physiology of trees limit the development of more effective management strategies to mitigate drought effects on forests. Here, we highlight some of the basic research needed to better understand tree drought physiology and how new technologies and interdisciplinary approaches can be used to address them.

Growing at the arid edge: Anatomical variations in leaves are more extensive than in stems of five Mediterranean species across contrasting moisture regimes.

Premise: Increasing aridity in the Mediterranean region affects ecosystems and plant life. Various anatomical changes in plants help them cope with dry conditions. This study focused on anatomical differences in leaves and xylem of five co-occurring Mediterranean plant species namely Quercus calliprinos, Pistacia palaestina, Pistacia lentiscus, Rhamnus lycioides, and Phillyrea latifolia in wet and dry sites.

Leaf membrane leakage and xylem hydraulic failure define the point of no return in drought-induced tree mortality in Cupressus sempervirens.

Measurements of resistance to embolism suggest that Cupressus sempervirens has a stem xylem that resists embolism at very negative water potentials, with 50% embolism (P) at water potentials of approximately -10 MPa. However, field observations in a semi-arid region suggest tree mortality occurs before 10% embolism. To explore the interplay between embolism and plant mortality, we conducted a controlled drought experiment involving two types of CS seedlings: a local seed source (S-type) and a drought-resistant clone propagated from a semi-arid forest (C-type).

Exploring interspecific hybridization dynamics in artificial forests of Pinus brutia and P. halepensis: Implications for sustainable afforestation.

Interspecific hybridization increases genetic diversity, which is essential for coping with changing environments. Hybrid zones, occurring naturally in overlapping habitats of closely related species, can be artificially established during afforestation. The resulting interspecific hybridization may promote sustainability in artificial forests, particularly in regions facing degradation due to climate change.

Carbohydrate dynamics in Populus trees under drought: An expression atlas of genes related to sensing, translocation, and metabolism across organs.

In trees, nonstructural carbohydrates (NSCs) serve as long-term carbon storage and long-distance carbon transport from source to sink. NSC management in response to drought stress is key to our understanding of drought acclimation. However, the molecular mechanisms underlying these processes remain unclear.

Guard cell activity of PIF4 and HY5 control transpiration.

Whole-plant transpiration, controlled by plant hydraulics and stomatal movement, is regulated by endogenous and environmental signals, with the light playing a dominant role. Stomatal pore size continuously adjusts to changes in light intensity and quality to ensure optimal CO intake for photosynthesis on the one hand, together with minimal water loss on the other. The link between light and transpiration is well established, but the genetic knowledge of how guard cells perceive those signals to affect stomatal conductance is still somewhat limited.

Analysis of seed coat development elucidates the genetic basis of metabolome and transcriptome underlying seed coat permeability characteristics.

The seed coat takes an important function in the life cycle of plants, especially seed growth and development. It promotes the accumulation of nutrients inside the seed and protects the seed embryo from mechanical damage. Seed coat permeability is an important characteristic of seeds, which not only affects seed germination, but also hinders the detection of seed vigor by electrical conductivity (EC) method.

Strategic roadmap to assess forest vulnerability under air pollution and climate change.

Although it is an integral part of global change, most of the research addressing the effects of climate change on forests have overlooked the role of environmental pollution. Similarly, most studies investigating the effects of air pollutants on forests have generally neglected the impacts of climate change. We review the current knowledge on combined air pollution and climate change effects on global forest ecosystems and identify several key research priorities as a roadmap for the future.

Transcriptome profiling reveals the effects of drought tolerance in Giant Juncao.

Background: Giant Juncao is often used as feed for livestock because of its huge biomass. However, drought stress reduces forage production by affecting the normal growth and development of plants. Therefore, investigating the molecular mechanisms of drought tolerance will provide important information for the improvement of drought tolerance in this grass.

Rapid starch degradation in the wood of olive trees under heat and drought is permitted by three stress-specific beta amylases.

Carbon reserve use is a major drought response in trees, enabling tree survival in conditions prohibiting photosynthesis. However, regulation of starch metabolism under drought at the whole-tree scale is still poorly understood. To this end, we combined measurements of nonstructural carbohydrates (NSCs), tree physiology and gene expression.

Sucrose-induced stomatal closure is conserved across evolution.

As plants evolved to function on land, they developed stomata for effective gas exchange, for photosynthesis and for controlling water loss. We have recently shown that sugars, as the end product of photosynthesis, close the stomata of various angiosperm species, to coordinate sugar production with water loss. In the current study, we examined the sugar responses of the stomata of phylogenetically different plant species and species that employ different photosynthetic mechanisms (i.

Transcriptome analysis of Pinus halepensis under drought stress and during recovery.

Forest trees use various strategies to cope with drought stress and these strategies involve complex molecular mechanisms. Pinus halepensis Miller (Aleppo pine) is found throughout the Mediterranean basin and is one of the most drought-tolerant pine species. In order to decipher the molecular mechanisms that P.

Suppression of sucrose synthase affects auxin signaling and leaf morphology in tomato.

Metabolic enzymes have been found to play roles in plant development. Sucrose synthase (SUS) is one of the two enzyme families involved in sucrose cleavage in plants. In tomato, six SUS genes have been found.

The Solanum tuberosum KST1 partial promoter as a tool for guard cell expression in multiple plant species.

To date, guard cell promoters have been examined in only a few species, primarily annual dicots. A partial segment of the potato (Solanum tuberosum) KST1 promoter (KST1 partial promoter, KST1ppro) has previously been shown to confer guard cell expression in potato, tomato (Solanum lycopersicum), citrus [Troyer citrange (C. sinensis×Poncirus trifoliata)], and Arabidopsis (Arabidopsis thaliana).

Grapevine acclimation to water deficit: the adjustment of stomatal and hydraulic conductance differs from petiole embolism vulnerability.

Drought-acclimated vines maintained higher gas exchange compared to irrigated controls under water deficit; this effect is associated with modified leaf turgor but not with improved petiole vulnerability to cavitation. A key feature for the prosperity of plants under changing environments is the plasticity of their hydraulic system. In the present research we studied the hydraulic regulation in grapevines (Vitis vinifera L.

Indirect Evidence for Genetic Differentiation in Vulnerability to Embolism in Pinus halepensis.

Climate change is increasing mean temperatures and in the eastern Mediterranean is expected to decrease annual precipitation. The resulting increase in aridity may be too rapid for adaptation of tree species unless their gene pool already possesses variation in drought resistance. Vulnerability to embolism, estimated by the pressure inducing 50% loss of xylem hydraulic conductivity (P 50), is strongly associated with drought stress resistance in trees.

Grapevine petioles are more sensitive to drought induced embolism than stems: evidence from in vivo MRI and microcomputed tomography observations of hydraulic vulnerability segmentation.

The 'hydraulic vulnerability segmentation' hypothesis predicts that expendable distal organs are more susceptible to water stress-induced embolism than the main stem of the plant. In the current work, we present the first in vivo visualization of this phenomenon. In two separate experiments, using magnetic resonance imaging or synchrotron-based microcomputed tomography, grapevines (Vitis vinifera) were dehydrated while simultaneously scanning the main stems and petioles for the occurrence of emboli at different xylem pressures (Ψx ).

Capsicum annuum S (CaS) promotes reproductive transition and is required for flower formation in pepper (Capsicum annuum).

The genetic control of the transition to flowering has mainly been studied in model species, while few data are available in crop species such as pepper (Capsicum spp.). To elucidate the genetic control of the transition to flowering in pepper, mutants that lack flowers were isolated and characterized.

De novo assembly and characterization of the transcriptome of the parasitic weed dodder identifies genes associated with plant parasitism.

Parasitic flowering plants are one of the most destructive agricultural pests and have major impact on crop yields throughout the world. Being dependent on finding a host plant for growth, parasitic plants penetrate their host using specialized organs called haustoria. Haustoria establish vascular connections with the host, which enable the parasite to steal nutrients and water.

Substantial roles of hexokinase and fructokinase in the effects of sugars on plant physiology and development.

The basic requirements for plant growth are light, CO2, water, and minerals. However, the absorption and utilization of each of these requires investment on the part of the plant. The primary products of plants are sugars, and the hexose sugars glucose and fructose are the raw material for most of the metabolic pathways and organic matter in plants.

Hexokinase mediates stomatal closure.

Stomata, composed of two guard cells, are the gates whose controlled movement allows the plant to balance the demand for CO2 for photosynthesis with the loss of water through transpiration. Increased guard-cell osmolarity leads to the opening of the stomata and decreased osmolarity causes the stomata to close. The role of sugars in the regulation of stomata is not yet clear.

Hexose kinases and their role in sugar-sensing and plant development.

Hexose sugars, such as glucose and fructose produced in plants, are ubiquitous in most organisms and are the origin of most of the organic matter found in nature. To be utilized, hexose sugars must first be phosphorylated. The central role of hexose-phosphorylating enzymes has attracted the attention of many researchers, leading to novel discoveries.

CaHAM is autoregulated and regulates CaSTM expression and is required for shoot apical meristem organization in pepper.

The angiosperm shoot apical meristem (SAM) is characterized by tightly organized cell layers and zones. The SAM's organization allows it to maintain its indeterminate nature while producing determinate lateral organs. Alterations in SAM gene expression partly account for the immense diversity in plant architecture.

The SlFRK4 promoter is active only during late stages of pollen and anther development.

Carbohydrates are essential for male gametophyte development. However, our understanding of the mechanism by which the sugar supply is controlled in the stamen is still in its infancy. We previously reported on the stamen-specific expression of the tomato (Solanum lycopersicum) sugar metabolic gene, fructokinase 4 (SlFRK4).