Functional Plant Biology

Reversible shrinking of the vacuole (vacuolar convolution) has been suggested as an adaptive mechanism of plants against high soil salinity and drought. Mechanisms of vacuolar convolution are poorly understood, mainly because of difficulties in examining the vacuole in its native environment. Elucidating these mechanisms may help in obtaining better drought and salinity resistance in crops in the face of climatic changes.

We urgently need to find solutions to the increasing problem of saline soils, which reduce crop productivity and lead to desertification. Atriplex halimus (salt brush) is a highly salt tolerant plant: we find populations from contrasting salinity environments switch on internal coping mechanisms at different times. Understanding how salt tolerant plants cope with salt stress will help us select the best plants for re-introduction into saline-affected areas.

Acclimation of leaf structure and photosynthesis are important responses to light availability but have not been widely investigated in plants with tall, linear leaves. Here, the tall wetland plant Typha latifolia acclimated to high light with high photosynthesis rates and investment in pigments that avoid damage by excess light. These findings help explain why these plants are more highly productive than many other species.

The survival strategies of bamboo species are driven by the changed precipitation pattern and seasonal drought. In this paper, we demonstrate the anisohydric behavior of Bambusa chungii stomata to maximize carbon assimilation, and show that that they exhibit structural compensation to maintain the hydraulic safety during the whole period of senescence. These results suggest that bamboo species could be dominant in the forest ecosystems in the future.

Sucrose transport within a plant involves the uploading of sucrose in the source tissue and unloading in sink tissue. The production of transgenic plants assisted with identifying the role of a sugarcane sucrose transporter in the sucrose mobilisation pathway. This sugarcane sucrose transporter does not directly load sucrose for transport but likely retrieves sucrose from intercellular spaces in both source and sink tissue.

Leaf photosynthesis is intimately associated with plant biomass production, yield development and the global carbon cycle. Biotic carbon sequestration is being considered a viable option for mitigating increasing atmospheric carbon dioxide emission, where photosynthesis plays a significant role. The wheat variety; WH-1021 with higher photosynthetic efficiency, δ¹³C isotopic discrimination, stomatal frequency and grain yield can be recommended for climate smart agriculture.

The machinery to synthesise the most abundant component of the biosphere – cellulose, is considered to involve distinct sets of CESA proteins to form primary versus secondary cell walls. Analysis of gene co-expression revealed that cellulosic fibres harbour both CESA sets while depositing tertiary cell wall. Thus, the original dogma needs refining and the mechanism to fine-tune cellulose synthesis organisation needs further elucidation.

Root system architecture is the spatial arrangement of roots that impact the capacity of plants to access nutrients and water. We employed pharmacologically generated morphological and molecular phenotypes and used in situ ¹⁵N isotope labelling to test the hypothesis that the contrasting root traits were functionally related to N acquisition. We demonstrated that root proliferation in response to external nitrate is a behaviour which integrates local N availability and the systemic N status of the plant.

A new approach to monitoring leaf photosynthesis in situ using 30 ms chlorophyll fluorescence transients at ~ 2 s intervals at distances up to 2 m is described. By monitoring fluorescence with near full reduction of Q_A (the primary quinone acceptor of PSII) these transients deliver parameters not directly available from other methods (relative functional absorption cross section of photosystem II, rates of intersystem electron transport and relative oxidation state the plastoquinone (PQ) pool). These permit non-intrusive evaluation of brief sun flecks in shade canopies whereas calibration against traditional PAM methods is obtained in longer protocols achieving full reduction of PQ.

Elongation-induced leaf emergence (escape strategy) is hypothesised to be more beneficial under single long-term submergence than under repeated short-term submergence. We tested this idea in Chloris gayana Kunth. grass. We found that under a single 2-week submergence event, plants accumulated a 2.9-fold higher dry mass than when experiencing the same submergence duration in separate events along 1 week, validating our hypothesis.

Ozone has been proposed as a convenient elicitor against pathogens. We hypothesised that ozone treatment may elicit defence against Blumeria graminis f. sp. tritici (Bgt) by inducing ROS signalling or other defence routes in wheat. We found that ozone treatment was effective in diminishing Bgt invasion in the susceptible cultivar, which was plausibly related to the SA pathway.

Mineral transport in plants is typically studied using chemical tracer compounds. However, after grape berries begin to ripen, xylem mobile tracers are often constrained to the vasculature near the proximal end. Here we show it is possible to observe the transport of important minerals, such as Mn, using magnetic resonance imaging.

Floranthene (FLT), a polycyclic aromatic hydrocarbons (PAH) poses a potential ecological risk to plants by damaging their photosynthetic machinery. It inhibits PSII while PSI protects itself from the damaging effects of FLT by initiating cyclic electron flow. This important information was provided using a very quick, noninvasive and simple technique of chlorophyll a fluorescence measurement.

Both phosphatidic acid (PA) and guanine nucleotide exchange factors (GEFs) are essential signalling molecules in adaptive response to various external stresses. Here we show that PA binds specifically to GEF8, thus regulating the activity of small GTPase ROPs in Arabidopsis. Our findings identify a direct functional regulation of lipid-mediation of GEFs activity and small GTPase signalling in cells.

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).

Drought and cold are two major factors limiting the growth of cool-season grasses and cause declines in grassland and forage quality. This study investigated the physiological and biochemical responses of one native grass species – Festuca sinensis – in China to temperature and water stress. Our results showed this grass could adapt to certain changes in the ecological environment by regulating their physiological and biochemical reactions.

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.

This work investigated physiological mechanisms conferring barley adaptation to combined waterlogging and salinity stress. Plants exposed to combined stress showed a negative correlation between shoot Na⁺ accumulation and the extent of salinity damage. Overall, the reported results indicated that K⁺ reduction in the plants but not stress-induced Na⁺ accumulation in the shoot was the most critical feature determining the overall plant performance under combined stress conditions.

Rice seeds are able to germinate under water, also thanks to their ability to produce α-amylase under O₂ shortage, thus allowing starch degradation. Calcineurin B-like interacting protein kinase 15 (CIPK15) was previously identified as a positive regulator of α-amylase induction during anaerobic germination. In this study, we describe calcineurin B-like proteins 4 (CBL4) as a CIPK15 partner under low O₂.

Aluminium (Al) toxicity is a significant problem for plant growth and production on acidic soils, which cover over 40% of the world’s arable land. In this study, we investigated the role of melatonin in soybean resistance to Al toxicity. The application of melatonin alleviated Al toxicity through enhancement of antioxidant enzymes activities and organic acid anions exudation.

Potassium (K) is one of the limiting factors that influenced rice growth and yield in submergence prone soils. Here we show that application of K at a higher dose (40 kg K₂O ha^–1 (basal) + one foliar spray at 0.5% K at panicle initiation stage) was beneficial in improving rice survival and grain yield. This finding will aid in boosting rice productivity in submergence prone rainfed ecology of Eastern Indo-Gangetic Plain.

Leaf gas exchange is commonly manipulated using low O₂ to suppress photorespiration but the detailed effects of this condition on leaf metabolism have often been disregarded. In this study, we used metabolomics to show metabolic alterations typical of a hypoxic response and that the aspartate pathway, including methionine synthesis, is sensitive to the O₂ mole fraction. These results provide evidence that, contrary to common belief, leaf catabolism and biosyntheses are sensitive to gaseous conditions.

Halophytes represent extraordinary strategies of flooding tolerance, most of them poorly understood. Traits associated with internal tissue aeration are often essential to submergence tolerance but the present study shows that other traits may also be relevant in order to sustain growth under recurrent submergence. Understanding traits that confer flooding tolerance is important in times with global climate changes that worldwide are predicted to result in more frequent flooding events.

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.

Climate changes result in more floods also in regions where the mean precipitation is predicted to decline. Dryland crops such as wheat and barley are particularly vulnerable to submergence stress. Here, we show that superhydrophobic leaf surfaces enhance survival of completely submerged wheat by formation of thin leaf gas films that helps wheat to ‘breathe’ under water.

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.

A barrier to radial oxygen loss (ROL) in roots is an important adaptation of many wetland plants growing in waterlogged, anoxic soils; however, knowledge of the nature of the barrier is sparse. The ROL barrier enhances longitudinal oxygen diffusion through aerenchyma to the root tip. Our comparison of two Hordeum marinum accessions differing in ROL barrier strength showed that the deposition of suberin into walls of the root exodermis is associated with reduction in loss of oxygen from basal root zones to the external medium.

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.

Flooding generally poses a threat to terrestrial plants, but wetland species display adaptations that prevent damage by the adverse conditions imposed by floods. One of these adaptations – formation of adventitious roots that replace the original non-adapted root system – may be severely constrained if insufficient light or contact of leaves with the atmosphere is present during the flooding event. This results in significantly fewer adventitious roots growing out of the stem, and thus poor performance in these stressful conditions.

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.

Some terrestrial plants, including wheat (Triticum aestivum), possess superhydrophobic leaf surfaces that retain a thin gas film when submerged. We tested gas film retention time of 14 different wheat cultivars and found that wheat could retain the gas films for a minimum of 2 days. We suggest that leaf gas film is a relevant trait to use as a selection criterion to improve the flood tolerance of crops that become temporarily submerged.

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.