Functional Plant Biology

It is uncertain how elevated CO₂ will affect photosynthesis during extreme events. Seven genotypes of Eucalyptus camaldulensis var. camaldulensis were grown in 400 or 640 parts per million CO₂, and photosynthetic electron transport, stomatal conductance and net CO₂ uptake were measured before, during and after a 4-day heatwave. The correlations between climate of origin and physiological responses depend on growth CO₂, which makes it difficult to predict species responses to episodic aspects of climate change.

Rice is a staple food in many countries and local production is carried out under unfavourable conditions, so effective and affordable alternatives to enhance local production are mandatory to palliate hunger. The underlying hypothesis is that certain beneficial bacterial strains can boost plant’s adaptive metabolism to overcome environmental limitations, so this study aimed to identify bacterial genes involved in beneficial effects on plants by creating random mutants of an effective Pseudomonas strain by evaluating loss of protection against salt stress in rice, and growth of tomato. Mutants were mapped and putative responsible genes sequenced. This study reveals the effectiveness of beneficial bacteria on two relevant crops, phylogenetically distant, so it appears as a challenging alternative to meet food security.

Leaf respiration (R) is an important determinant of tree and forest function, yet the impacts of rising atmospheric CO₂ on leaf R remain poorly understood. We found that leaf respiration is largely unaffected by elevated CO₂, and is relatively similar across seedlings of geographically and climatically diverse populations of Eucalyptus grandis. We conclude that elevated CO₂ is unlikely to change leaf R in E. grandis.

Soil water availability is a key factor limiting rates of carbon assimilation in plants. However, we found that as water availability declined, investment in foliar nitrogen, photosynthetic capacity and intrinsic water-use efficiency increased across eight co-occurring tree species in semiarid Australia. We conclude that differential access to water is an important factor driving variability of traits related to carbon gain.

The mechanism by which flowers regulate their function and structure to maintain water balance is unclear. We found that flowers of two Magnolia species consumed less than half the water that leaves did, and explored different hydraulic strategies in flowers and leaves to sustain hydraulic safety. This study contributes new knowledge to the field of floral hydraulics.

Photorespiration plays a positive role in coping with drought stress in plants. Here, the drought-tolerant plant Caragana korshinskii responded to drought with high photorespiration and strong antioxidative system that may improve the ability of coping with drought. These findings help us further understand how photorespiration and antioxidative systems co-ordinate to improve the tolerance to drought in plants.

Resurrection plants exposed to extreme dehydration are able to recover physiological functionality after rehydration, because of their ability to induce protection and repair mechanisms. We demonstrated that the Brazilian semiarid grass Tripogon spicatus is able to tolerate complete vegetative dehydration, maintaining chlorophyll content and increasing photosynthetic rates after rehydration.

The stable co-existence of a diversity of plant species within a single biome is possible if the species access different resources. In semiarid Australia we found that co-occurring tree species had differing access to water, resulting in multiple plant water-use strategies in this water-limited environment. These differing strategies have important implications for the survival of these species under drought.

Reproductive growth is very important for plant survival and population establishment under salinity. It remains unknown whether the reproductive process of Suaeda salsa is affected by salinity. NaCl markedly increased the reproductive growth of S. salsa by increasing flower number and fertility. Unravelling the mechanisms of plant salt tolerance will be helpful for improving agricultural production.

Ethylene-induced abscission of young cotton fruits is a major lint yield limiting factor in cotton crop production under stressed environments. Extreme weather events such as long-term soil waterlogging and elevated CO₂ can increase fruit loss caused by ethylene production in cotton. Our study showed that the physiological and yield performance of cotton crops under future environments can potentially be improved by mitigating ethylene action.

Salinity is a major factor affecting crop production worldwide. We identified enzymatic and genetic mechanisms in maize that confer tolerance against abiotic stresses when inoculated with plant growth-promoting bacteria. Inoculation with the elite strains identified in this study, of Azospirillum brasilense (Ab-V6) and Rhizobium tropici (CIAT 899) might represent a valuable and sustainable strategy to mitigate salinity stress.

In this work we tested the response of PEPC and NAD-ME in the C₄-NAD-ME subtype plant Salsola lanata (Chenopodiaceae) under drought stress. Only severe stress limited PEPC enzyme activity (at pH 8.0) significantly, and this was related with decreased PEPC mRNA. More phosphorylated status of PEPC enzyme in plants is under moderate stress compared with other treatments. The change of NAD-ME activity coincided with a change of leaf water content rather than the amount of α-NAD-ME mRNA and protein.

By 2015 genetically modified (GM) crops had been commercialised for 20 years. This technology ranks amongst the most rapidly accepted by farmers, but are there downsides to these introductions? This review considers the advantages and potential disadvantages of GM crops.

Gibberellins (GAs) promote hypocotyl elongation by controlling the expression of many genes in plants. However, only a few target genes of GAs have been identified to date. The paper provides strong evidence that tonoplast aquaporin AtTIP5;1 mediates GA-stimulated hypocotyl cell elongation under excess boron condition in Arabidopsis. The finding highlights the essential roles of vacuoles and boron in GA signalling in plants.

Salinity is a global problem affecting agriculture. Here we show that overexpression of vacuolar ATPase subunit C is beneficial in improving barley performance under saline conditions. This effect is explained by transgenic lines being able to rely more on the use of Na⁺ and K⁺ for osmotic adjustment rather than spending energy for de novo synthesis of organic osmolytes.

Salinity reduces the grain yield of cereal crops. In this study, nondestructive and destructive phenotyping was used to evaluate 24 predominately Australian barley lines at 0, 150 and 250 mM NaCl. Lines with higher salinity tolerance were better able to maintain their growth rates shortly after salt treatment and exclude Na⁺ from their shoots. This study shows that variation in shoot tolerance mechanisms unrelated to ion toxicity exists in barley and suggests that breeding new varieties with increased shoot ion-independent tolerance is possible.

Rainfall pulses in water-limited regions significantly affect ecosystem structure and function. After comparing the effects of size and timing of stimulated rainfall pulses on dominant grassland species, we concluded that small pulses had a greater effect on leaf photosynthesis rather than biomass production, and the magnitude was correlated with species type and growth season. These results facilitate the regional eco-adaptability evaluation of species and prediction of vegetation succession under altered rainfall regimes.

Interspecific differences in photosynthetic attributes of Chardonnay and Merlot grapevines have been established. The cause of such differences were attributed to a higher carboxylation and regeneration capacity in the Merlot leaves, especially at high temperatures and cultivar differences were exacerbated as the season progressed. Differences in biochemical processes related to assimilation at high temperatures were measured between the cultivars, and these may relate to inherent differences in temperature tolerance between these closely related cultivars.

Rising atmospheric [CO₂] and temperature under projected climate change scenarios may have significant impacts on the physiology and yield of cotton. We quantified the response of cotton cultivars grown in elevated [CO₂] and temperature and found substantial potential to increase breeding selection in future climates. Understanding the implications of integrated environmental impacts on cotton is critical for developing cotton systems that are resilient to stresses induced by climate change.

Prolonged endoplasmic reticulum (ER) stress oxidises the cellular glutathione pool. To elucidate the role of glutathione during ER stress, biosynthesis and degradation of glutathione and activities of related enzymes were evaluated. Our data demonstrated that glutathione biosynthesis and an apoplastic but not cytoplasmic catabolic pathway was induced. In addition, the activities of enzymes that use glutathione as a substrate were increased by ER stress.

Heavy metals disrupt pollen germination in many species, but the mechanism of their action remained unstudied. Here we report that Cu²⁺ and Ni²⁺ affect H⁺ current and K⁺ current, respectively, in lily pollen protoplasts; Cu²⁺ as well enhances reactive oxygen species accumulation. Thus, we reveal the targets for heavy metals (Cu²⁺ and Ni²⁺) in the pollen grain plasma membrane.

Leaf respiration is an integral component of plant growth and the global carbon cycle, and it is typically lower during the day than at night. We investigated leaf respiration in Mediterranean holm oak woodland, and found that light inhibition was not strongly related to changes in soil water content or ambient temperature. The findings have implications for predictive models that seek to calculate plant carbon balance.

Horn-shaped gall is of great value in food, medicine and the industrial field, so the control of its formation will be helpful to increase the products. Vacuolar invertase is related to the rapid expansion of the galls, but ionically bound cell wall invertase is involved in the rapid growth of tissues. This might also be found in other kinds of galls.

Signalling is a central phenomenon in biology. It is crucial to all aspects of plant physiology including growth, development and interactions with the environment. Here, novel hypotheses and experimental data regarding signalling hubs, second messengers, programmed cell death and autophagy are presented from the Fourth Plant Signalling and Behaviour Symposium in Sankt Petersburg, Russia, June 2016).

Arabidopsis myotubularins AtMTM1 and AtMTM2 control stomata movements via reactive oxygen species (ROS) homeostasis under drought stress. Acting as a secondary messenger in the ABA-induced ROS production in guard cells, PtdIns5P emerges as an evolutionarily conserved signalling molecule downstream of AtMTMs calibrating cellular ROS levels under stress. AtMTM1 and AtMTM2 activities balance ABA-induced ROS and cellular homeostasis under dehydration stress.

Peroxisomes balance the cellular levels of reactive oxygen species (ROS) and therefore should modulate ROS-regulated programs like autophagy or cell death. We used tobacco suspension cultures to show that degradation of peroxisomes via autophagy was a prerequisite for cell death and depended on the levels of the major peroxisomal protein, catalase. This suggests a role of plant catalase in the regulation of peroxisome turnover and autophagic cell death.

The electrophysiological response pattern of Nitellopsis obtusa cell can be assessed to evaluate the effect of many biologically active compounds. We illustrate a variety of electrophysiological approaches for the investigations of electrical signaling after chemical treatment in vivo. The insights about the Characean model system are likely to hold for plants in general and even deepen the understanding of the plant evolution.

Although many studies established nitric oxide (NO) as a signaling molecule in plants, the identification of target molecules of NO has remained elusive due to the lack of in depth molecular studies. Our quantitative proteome analysis suggests the differential regulation of 248 proteins and dynamic regulation of metabolic pathways by exogenous NO donor in chickpea. This is the first report in legumes pointing at the potential candidates that attribute the reported functions of NO in plants.

We studied the dynamics of photochemical activity in seed coats and cotyledons during development of yellow- and green-seeded pea cultivars by using the pulse amplitude modulation fluorometric analysis. The fast transients of the chlorophyll a fluorescence revealed higher photochemical activity in the coats of yellow-seeded cultivar at the early- and middle cotyledon stages of seed development in comparison to those observed in the green-seeded ones. Photochemical activity in the cotyledons of both cultivars could not be any more detected at the late cotyledon stage. This process was triggered by dehydration of seed tissues.

Root growth is controlled by phytohormones, but what cellular processes are regulated and how it occurs is still an open question. Here it is shown that cytokinin affects root growth mainly through its effect on cell proliferation, and does not initiate the transition of cells to differentiation as previously thought. Cellular analysis performed could be applied for the analysis of how any plant hormone influences developmental processes in plant roots.

Intracellular communications in plant cells of large dimensions rely primarily on cytoplasmic streaming, because diffusion is too slow for the transport on mm-scale distances. Illumination of a small cell spot at a various distances from the point of chlorophyll fluorescence measurements revealed the wave-like propagation of the fluorescence response along the cell length. The results show that the photosynthetic function of immobile chloroplasts under constant light can be affected by long-distance transmission of a photosynthetically active metabolite from the remote cell parts.

Understanding the molecular mechanisms of plant development constitutes an important field of investigations in the current era of plant biology research. Nitric oxide signalling regulates a variety of biochemical processes in plants. Present review provides an in-depth analysis of our current understanding on the subject, particularly with reference to plant growth under stress conditions.

Melatonin is an important hormone and signalling molecule in all forms of life including humans, plants and bacteria. Recent plant physiology and genomic experiments have described the redirection of plant growth and metabolism, and demonstrated a diversity of genes involved in response to melatonin, however, the exact metabolic cascades that translate melatonin signals into physiological responses is not fully understood. This review provides an overview of melatonin mediated signalling manifested as behaviours and its roles in basic and industrial research.

Memristors, or resistors with memory, exist in vivo as components of plasma membranes in plants, fruits, roots and seeds. Authors found memristors in an androecium, spur, petals and pedicel in Sunpatiens flowers. The discovery of memristors in Sunpatiens (Impatiens spp.) creates a new direction in the modelling and understanding of electrophysiological phenomena and memory elements in flowers.

Plant fibres with a tertiary cell wall (G-layer) may function as plant ‘muscles’. Large-scale transcriptome profiling of isolated flax phloem fibres permitted to identify the major players and regulatory elements that operate during graviresponce specifically in the fibres of the pulling stem side. The suggested mechanisms of phloem fibre involvement in tropisms may considerably renew the concept of herbaceous plant behaviour upon gravistimulation.

Clarifying herbivory-induced plant cellular signalling is a critical step to push the research of plant-herbivore interaction forward. We review the role of ion channels/transporters in modulating herbivory-induced early signalling events and rapid systemic signal transmission in plants. This work provides a comprehensive source of information about plant defensive strategies upon attack.

Cytokinin is an important plant hormone and its mode of action has been extensively studied; however, to date, the subcellular localisation of cytokinin perception and signal transduction remains a matter of debate. This study describes cytokinin receptor–phosphotransmitter interaction and its subcellular localisation in living plant cells and it provides several experimental evidences for receptor activity at the endoplasmic reticulum (ER) membrane. It is concluded that intracellular cytokinins within the ER lumen may play an important role in cytokinin signalling, at least in some cell types.

Rhizobium bacteria, which live within the root nodules of legumes, allow plants to capture nitrogen gas from the atmosphere and use it for their own growth. Central to this symbiosis is an intracellular structure, called the symbiosome, in which nitrogen-fixing bacterial cells exchange components with the host cells that harbor them. Recent research on the differentiation of symbiosomes and of the infected cells that accommodate them has helped to decipher some general molecular mechanisms of cell differentiation.

Plants, like animals, produce electrical signals in response to various external influences. In this study we raised a question whether the electrical signals transmit information about the nature of the stimulus, and found out that different stimuli induce signals of varied parameters. The obtained results explain how plants adapt to changing environment.

Environmental stresses are main causes for low agricultural productivity. At the cellular level, stresses induce generation of reactive oxygen species (ROS), ion disequilibrium, autophagy and programmed cell death (PCD). Here we propose that these processes interact and that ROS and ion disequilibrium are triggers of autophagy and PCD. Overall, presented data contribute to understanding plant stress physiology.

Transient elevation of cytosolic Ca²⁺, also referred as a Ca²⁺signal, is as central phenomenon of plant signalling. Plants evolved sophisticated systems to initiate, amplify and terminate Ca²⁺ signals. Structure and properties of these systems, including Ca²⁺-permeable ion channels, Ca²⁺-ATPases, Ca²⁺/H⁺ exchangers and ‘ROS-Ca²⁺ hub’ are discussed here. They provide a fine-tuned mechanism for encoding diverse external and internal stimuli.

Focussed ion bean scanning electron microscopy (FIB-SEM) is a technique that can be used to generate 3D renderings of cells and their contents. Although FIB-SEM has been regularly used to investigate animal cells and tissues, it has rarely been deployed to study plant structures. Here we demonstrate that FIB-SEM can easily be used to study plant samples and have discovered previously unknown arrangements of organelles and membranes in those samples.

Photosynthetic electron transport chain is not only source of ATP and NADPH for photosynthesis; it is a sensor, informing adaptation systems of plant about environmental changes. An important transmitter of this information is hydrogen peroxide whose mechanisms of formation are presented, laying special emphasis on the formation outside and within thylakoid membrane. It is discussed, that the formation place can ensure definite signal about the specific environmental change.

Although plant proteases of the phytaspase family are important contributors to stress-induced plant cell death, phytaspase of a classical model plant Arabidopsis thaliana has escaped identification thus far. We identified the Arabidopsis phytaspase-encoding gene and characterised the recombinant enzyme. Substrate specificity and properties of the Arabidopsis phytaspase display both important similarities with and distinctions from the already characterised phytaspases.

Cyclic GMP (cGMP) signalling in plants is crucial for many physiological processes. Recent analytical and genomic developments now allow detailed studies into the biochemistry and physiological role of cGMP in plants, and the latest findings are reviewed in this article.

Large conductance SV/TPC1 channels are ubiquitously and abundantly expressed in the vacuolar membranes of higher plants. They are unique established Ca²⁺-permeable channels in vacuoles, but their activity is strongly negatively controlled, so that they were believed to be inactive or to act only locally. Recent evidence suggests the key role of SV/TPC1 channels in the long-distance Ca²⁺ signalling.

Plants adapt to environmental light conditions with the use of the sophisticated phytochrome system. In this work, polymorphism of its major component – phytochrome A– was investigated. With the use of transgenic Arabidopsis and fluorescence technique, it was shown that two molecular types of the photoreceptor differ by the state of phosphorylation and their existence accounts for its complex functions.

The ABA-deficient barley mutant Az34 and wild type (WT) were exposed to air warming. Although transpiration rate of both genotypes increased, leaf water potential decreased in the mutant but was maintained in WT plants. Only WT plants showed increased root ABA accumulation, which increased root hydraulic conductivity and aquaporin abundance, which seems important in maintaining leaf hydration.