Search

Plants face fluctuations in environmental conditions throughout their life cycles. Some of these conditions, such as CO2 concentration and increasing temperature, are closely linked to ongoing climate change. These conditions not only affect plant growth and development but also modify the response to sudden exposure to stressors through morphological, physiological, and biochemical acclimation. Understanding these responses is therefore important for defining adaptation strategies for future crop production. In this study, we tested the acclimation effect of light intensity (low, high) and CO2 concentration (low, ambient, elevated) on barley plants and its implications for subsequent responses to drought, heat, and their combination. The acclimation to the growth conditions induced numerous changes both in plant morphology and physiology. The whole-plant leaf area was stimulated by increasing light intensity and CO2 concentration. That led to increased whole-plant transpiration despite the trend of stomatal conductance was the opposite in comparison to leaf area. The increased whole-plant transpiration then increased the sensitivity of barley plants to the stress treatments. Similarly, the stimulatory effect of high light intensity on antioxidative capacity was not sufficient to improve barley performance under the stress treatments. The presented results show that for physiological or biochemical indicators of stress tolerance to be realistically used to evaluate the expected response to stress conditions, they must be related to the morphology of the whole plant, which influences both the severity of stress and the quantitative role of resistance mechanisms.

Abstract Background The availability of soil phosphorus (P) often limits the productivities of wet tropical lowland forests. Little is known, however, about the metabolomic profile of different chemical P compounds with potentially different uses and about the cycling of P and their variability across space under different tree species in highly diverse tropical rainforests. Results We hypothesised that the different strategies of the competing tree species to retranslocate, mineralise, mobilise, and take up P from the soil would promote distinct soil 31P profiles. We tested this hypothesis by performing a metabolomic analysis of the soils in two rainforests in French Guiana using 31P nuclear magnetic resonance (NMR). We analysed 31P NMR chemical shifts in soil solutions of model P compounds, including inorganic phosphates, orthophosphate mono- and diesters, phosphonates, and organic polyphosphates. The identity of the tree species (growing above the soil samples) explained > 53% of the total variance of the 31P NMR metabolomic profiles of the soils, suggesting species-specific ecological niches and/or species-specific interactions with the soil microbiome and soil trophic web structure and functionality determining the use and production of P compounds. Differences at regional and topographic levels also explained some part of the the total variance of the 31P NMR profiles, although less than the influence of the tree species. Multivariate analyses of soil 31P NMR metabolomics data indicated higher soil concentrations of P biomolecules involved in the active use of P (nucleic acids and molecules involved with energy and anabolism) in soils with lower concentrations of total soil P and higher concentrations of P-storing biomolecules in soils with higher concentrations of total P. Conclusions The results strongly suggest “niches” of soil P profiles associated with physical gradients, mostly topographic position, and with the specific distribution of species along this gradient, which is associated with species-specific strategies of soil P mineralisation, mobilisation, use, and uptake.

This study examined the effect of the interactions of key factors associated with predicted climate change (increased temperature, and drought) and elevated CO2 concentration on C3 and C4 crop representatives, barley and sorghum. The effect of two levels of atmospheric CO2 concentration (400 and 800 ppm), three levels of temperature regime (21/7, 26/12 and 33/19°C) and two regimes of water availability (simulation of drought by gradual reduction of irrigation and well-watered control) in all combinations was investigated in a pot experiment within growth chambers for barley variety Bojos and sorghum variety Ruby. Due to differences in photosynthetic metabolism in C3 barley and C4 sorghum, leading to different responses to elevated CO2 concentration, we hypothesized mitigation of the negative drought impact in barley under elevated CO2 concentration and, conversely, improved performance of sorghum at high temperatures. The results demonstrate the decoupling of photosynthetic CO2 assimilation and production parameters in sorghum. High temperatures and elevated CO2 concentration resulted in a significant increase in sorghum above- and below-ground biomass under sufficient water availability despite the enhanced sensitivity of photosynthesis to high temperatures. However, the negative effect of drought is amplified by the effect of high temperature, similarly for biomass and photosynthetic rates. Sorghum also showed a mitigating effect of elevated CO2 concentration on the negative drought impact, particularly in reducing the decrease of relative water content in leaves. In barley, no significant factor interactions were observed, indicating the absence of mitigating the negative drought effects by elevated CO2 concentration. These complex interactions imply that, unlike barley, sorghum can be predicted to have a much higher variability in response to climate change. However, under conditions combining elevated CO2 concentration, high temperature, and sufficient water availability, the outperforming of C4 crops can be expected. On the contrary, the C3 crops can be expected to perform even better under drought conditions when accompanied by lower temperatures.

One of the key challenges linked with future food and nutritional security is to evaluate the interactive effect of climate variables on plants’ growth, fitness, and yield parameters. These interactions may lead to unique shifts in the morphological, physiological, gene expression, or metabolite accumulation patterns, leading to an adaptation response that is specific to future climate scenarios. To understand such changes, we exposed spring wheat to 7 regimes (3 single and 4 combined climate treatments) composed of elevated temperature, the enhanced concentration of CO2, and progressive drought stress corresponding to the predicted climate of the year 2100. The physiological and metabolic responses were then compared with the current climate represented by the year 2020. We found that the elevated CO2 (eC) mitigated some of the effects of elevated temperature (eT) on physiological performance and metabolism. The metabolite profiling of leaves revealed 44 key metabolites, including saccharides, amino acids, and phenolics, accumulating contrastingly under individual regimes. These metabolites belong to the central metabolic pathways that are essential for cellular energy, production of biosynthetic pathways precursors, and oxidative balance. The interaction of eC alleviated the negative effect of eT possibly by maintaining the rate of carbon fixation and accumulation of key metabolites and intermediates linked with the Krebs cycle and synthesis of phenolics. Our study for the first time revealed the influence of a specific climate factor on the accumulation of metabolic compounds in wheat. The current work could assist in the understanding and development of climate resilient wheat by utilizing the identified metabolites as breeding targets for food and nutritional security.

To investigate the different responses of crops to drought stress under field conditions of Central European Climate for selected crop rotations, a field experiment was conducted at a test site in the Czech Republic from 2014 to 2021. Depending on the crop, rainout shelters were placed in late spring and early summer to study the effects of drought in the final stages of crop development. Due to these rainout shelters and the associated lower water availability for the crops during the summer, a reduction in leaf area index, biomass and yield was observed. For example, a yield decrease of more than 30% was observed for spring barley, winter rape and winter wheat compared to conditions without rainout shelters. The reduction was 25% and 18% for winter rye and silage maize, respectively, under rainout shelters. Soil moisture played a significant role in yield, where a predictive model based on monthly soil moisture explained up to 79% (winter rape) of the yield variance.

In the Czech Republic, soil moisture content during the growing season has been decreasing over the past six decades, and drought events have become significantly more frequent. In 2003, 2015, 2018 and 2019, drought affected almost the entire country, with droughts in 2000, 2004, 2007, 2012, 2014 and 2017 having smaller extents but still severe intensities in some regions. The current methods of visiting cadastral areas (approximately 13,000) to allocate compensation funds for the crop yield losses caused by drought or aggregating the losses to district areas (approximately 1000 km2) based on proxy data are both inappropriate. The former due to the required time and resources, the later due to low resolution, which leads to many falsely negative and falsely positive results. Therefore, the study presents a new method to combine ground survey, remotely sensed and model data for determining crop yield losses. The study shows that it is possible to estimate them at the cadastral area level in the Czech Republic and attribute those losses to drought. This can be done with remotely sensed vegetation, water stress and soil moisture conditions with modeled soil moisture anomalies coupled with near-real-time feedback from reporters and with crop status surveys. The newly developed approach allowed the achievement of a proportion of falsely positive errors of less than 10% (e.g., oat 2%, 8%; spring barley 4%, 3%; sugar beets 2%, 21%; and winter wheat 2%, 6% in years 2017, resp. 2018) and allowed for cutting the loss assessment time from eight months in 2017 to eight weeks in 2018.

Agricultural practices applied to increase crop production and secure future food demands can have a large negative impact on the environmental quality. They should be, therefore, also evaluated in terms of an impact on soil organic carbon (C) content and greenhouse gas emissions. In this study, we investigated the combined effects of adaptation technology (AT) based on no-till crop sowing into cover crop mulch, nitrogen (N) fertilization, and external C supply in the form of biochar, compost, and composted biochar on soil CO2 efflux (Rs). Rs was measured using a closed gas-exchange system in biweekly to monthly intervals during 2 consecutive years when winter wheat (first year) and spring barley (second year) were cultivated. Biochar, compost, and composted biochar had no significant effects on Rs. N fertilization with the medium fertilizer dose tended to increase Rs compared to the control at the beginning of the growing season, followed by Rs decrease later in the season. On the other hand, fertilization with the maximum fertilizer dose mostly decreased Rs throughout the whole growing season. AT affected the dynamics of Rs substantially, depending on the year, site, and N fertilization, resulting in significant interactions between technology and date of measurement and also between site and technology. However, the mean effect of AT across the whole season was insignificant. The results show that the C increase in the soil that occurs after the application of compost and the combination of composted biochar application with AT is not accompanied by an increase in Rs and, thus, leads to at least short-term C storage in the soil. The reduction in CO2 emissions from soil to the atmosphere under AT represents a positive aspect of such management practice for mitigating climate change.

A multifactorial field experiment in an open-top chamber facility at the experimental station Domaninek was conducted in 2014 to understand the potential effects of climate change factors on the malting quality of spring barely and to evaluate the interactions of these factors with nitrogen nutrition. The results showed a major effect of nitrogen nutrition on malting quality. Nitrogen increased the protein content and impaired the key malting quality parameters such as a relative extract or Kolbach index. Elevated CO2 concentration had a generally positive effect on malting quality and alleviated the negative impact of nitrogen nutrition particularly. Reduced water availability had only a minor impact on malting quality; however, these effects were predominantly positive.

The relict arctic–alpine tundra provides a natural laboratory to study the potential impacts of climate change and anthropogenic disturbance on tundra vegetation. The Nardus stricta-dominated relict tundra grasslands in the Krkonoše Mountains have experienced shifting species dynamics over the past few decades. Changes in species cover of the four competing grasses—Nardus stricta, Calamagrostis villosa, Molinia caerulea, and Deschampsia cespitosa—were successfully detected using orthophotos. Leaf functional traits (anatomy/morphology, element accumulation, leaf pigments, and phenolic compound profiles), were examined in combination with in situ chlorophyll fluorescence in order to shed light on their respective spatial expansions and retreats. Our results suggest a diverse phenolic profile in combination with early leaf expansion and pigment accumulation has aided the expansion of C. villosa, while microhabitats may drive the expansion and decline of D. cespitosa in different areas of the grassland. N. stricta—the dominant species—is retreating, while M. caerulea did not demonstrate significant changes in territory between 2012 and 2018. We propose that the seasonal dynamics of pigment accumulation and canopy formation are important factors when assessing potential “spreader” species and recommend that phenology be taken into account when monitoring grass species using remote sensing.

Abstract The functional adaptive responses of higher plants to biotic interactions with herbivores and fungi have long been topics of research. One constraint to obtaining a comprehensive understanding of the most general plant responses, however, has been the difficulty of studying all plant functional shifts simultaneously due to analytical limitations. Now this is possible with the advent of metabolomics. Using 151 records from the WEB of SCIENCE database, we have analyzed the development and application of metabolomic profiles to ecological studies in the last two decades. We have used meta‐analysis and pathway enrichment analyses to assess the whole set of constitutive and inducible defenses. Constitutive defenses against herbivores were mainly based on a significant high level of the metabolism of several amino acids with parallel increases in the concentrations of flavones (phenolics) and saponins (glycosides). Inducible defenses, though, were mainly based on the increases in concentration of methyl‐ketone, pantothenate, and Coenzyme A. Butyrate metabolism and the mitochondrial electron‐transport chain were upregulated, in agreement with previous reports that herbivory‐activated plant chemical defenses were mainly based on jasmonic acid, salicylic acid, and ethylene‐associated pathways. The metabolic responses/acclimations to pathogenic fungi were mainly linked with increases in aspartate and pyruvate metabolism, the transfer of acetyl groups within mitochondria, and the upregulation of branched‐chain amino acids degradation pathways. These responses/acclimations were accompanied by higher concentrations of the most important groups of secondary metabolites such as phenolics (anthocyanins, flavonoids), quinones, alkaloids, terpenoids, and polyamines and other compounds related to antistress mechanisms such as proline. The leaves of mycorrhized plants accumulated nucleotide sugars, sphingolipids, and methylhistidine. These responses were associated with maintaining the integrity of plant cell membranes under fungal hypha penetration. The responses were accompanied by increases in the concentrations of phenolics, blumenols, and alkaloids and decreases in the concentrations of polyamines, consistent with the mycorrhizal inhibition of polyamines. This summary provides a clear synthesis of the most successful plant strategies selected after millions of years of evolution and will be a very promising tool for the management of crops and ecosystems and for selecting the main lines in breeding studies for future research.

Abstract Plant community biomass production is co‐dependent on climatic and edaphic factors that are often covarying and non‐independent. Disentangling how these factors act in isolation is challenging, especially along large climatic gradients that can mask soil effects. As anthropogenic pressure increasingly alters local climate and soil resource supply unevenly across landscapes, our ability to predict concurrent changes in plant community processes requires clearer understandings of independent and interactive effects of climate and soil. To address this, we developed a multispecies phytometer (i.e., standardized plant community) for separating key drivers underlying plant productivity across gradients. Phytometers were composed of three globally cosmopolitan herbaceous perennials, Dactylis glomerata, Plantago lanceolata, and Trifolium pratense. In 2017, we grew phytometer communities in 18 sites across a pan‐European aridity gradient in local site soils and a standardized substrate and compared biomass production. Standard substrate phytometers succeeded in providing a standardized climate biomass response independent of local soil effects. This allowed us to factor out climate effects in local soil phytometers, establishing that nitrogen availability did not predict biomass production, while phosphorus availability exerted a strong, positive effect independent of climate. Additionally, we identified a negative relationship between biomass production and potassium and magnesium availability. Species‐specific biomass responses to the environment in the climate‐corrected biomass were asynchronous, demonstrating the importance of species interactions in vegetation responses to global change. Biomass production was co‐limited by climatic and soil drivers, with each species experiencing its own unique set of co‐limitations. Our study demonstrates the potential of phytometers for disentangling effects of climate and soil on plant biomass production and suggests an increasing role of P limitation in the temperate regions of Europe.

Abstract Understorey plant communities are crucial to maintain species diversity and ecosystem processes including nutrient cycling and regeneration of overstorey trees. Most studies exploring effects of elevated CO2 concentration ([CO2]) in forests have, however, been done on overstorey trees, while understorey communities received only limited attention. The hypothesis that understorey grass species differ in shade‐tolerance and development dynamics, and temporally exploit different niches under elevated [CO2], was tested during the fourth year of [CO2] treatment. We assumed stimulated carbon gain by elevated [CO2] even at low light conditions in strongly shade‐tolerant Luzula sylvatica, while its stimulation under elevated [CO2] in less shade‐tolerant Calamagrostis arundinacea was expected only in early spring when the tree canopy is not fully developed. We found evidence supporting this hypothesis. While elevated [CO2] stimulated photosynthesis in L. sylvatica mainly in the peak of the growing season (by 55%–57% in July and August), even at low light intensities (50 µmol m−2 s−1), stimulatory effect of [CO2] in C. arundinacea was found mainly under high light intensities (200 µmol m−2 s−1) at the beginning of the growing season (increase by 171% in May) and gradually declined during the season. Elevated [CO2] also substantially stimulated leaf mass area and root‐to‐shoot ratio in L. sylvatica, while only insignificant increases were observed in C. arundinacea. Our physiological and morphological analyses indicate that understorey species, differing in shade‐tolerance, under elevated [CO2] exploit distinct niches in light environment given by the dynamics of the tree canopy.

To ensure the selection of wheat genotypes that are resilient to future climatic conditions, with drought already being the most significant and acute problem in many areas, twenty winter wheat cultivars were tested for drought stress tolerance from the beginning of stem elongation (DC 30; Zadoks decimal codes) for 49 days (until the stage of grain development, DC 73–75) within an automatic phenotyping platform. The control plants were regularly irrigated to 70% of soil water capacity (SWC), while the drought-stressed plants were subjected to controlled drying until the permanent wilting point (15% of SWC) was reached. Then, the drought-stressed plants were rewatered again to 70% of the maximum SWC. After they recovered, the plants were again exposed to ambient weather conditions. The final yield formation parameters were assessed at the fully ripe stage. Our results showed that the genotypes originating in Western Europe manifested the highest response to the experimentally set drought in the grain number per spike measurement, while the genotypes originating in the warmer regions of southeastern Europe manifested the highest response to the experimental drought mainly in thousand grain weight measurement. Similar response patterns were evident for late- and early-maturing genotypes. The results indicate the potential of selecting genotypes with increased drought resistance even within the existing set of cultivars.

Malting barley requires sensitive methods for N status estimation during the vegetation period, as inadequate N nutrition can significantly limit yield formation, while overfertilization often leads to an increase in grain protein content above the limit for malting barley and also to excessive lodging. We hypothesized that the use of N nutrition index and N uptake combined with red-edge or green reflectance would provide extended linearity and higher accuracy in estimating N status across different years, genotypes, and densities, and the accuracy of N status estimation will be further improved by using artificial neural network based on multiple spectral reflectance wavelengths. Multifactorial field experiments on interactive effects of N nutrition, sowing density, and genotype were conducted in 2011–2013 to develop methods for estimation of N status and to reduce dependency on changing environmental conditions, genotype, or barley management. N nutrition index (NNI) and total N uptake were used to correct the effect of biomass accumulation and N dilution during plant development. We employed an artificial neural network to integrate data from multiple reflectance wavelengths and thereby eliminate the effects of such interfering factors as genotype, sowing density, and year. NNI and N uptake significantly reduced the interannual variation in relationships to vegetation indices documented for N content. The vegetation indices showing the best performance across years were mainly based on red-edge and carotenoid absorption bands. The use of an artificial neural network also significantly improved the estimation of all N status indicators, including N content. The critical reflectance wavelengths for neural network training were in spectral bands 400–490, 530–570, and 710–720 nm. In summary, combining NNI or N uptake and neural network increased the accuracy of N status estimation to up 94%, compared to less than 60% for N concentration.

Changes in stomatal conductance and density allow plants to acclimate to changing environmental conditions. In the present paper, the influence of atmospheric CO2 concentration and light intensity on stomata were investigated for two barley genotypes—Barke and Bojos, differing in their sensitivity to oxidative stress and phenolic acid profiles. A novel approach for stomatal density analysis was used—a pair of convolution neural networks were developed to automatically identify and count stomata on epidermal micrographs. Stomatal density in barley was influenced by genotype, as well as by light and CO2 conditions. Low CO2 conditions resulted in increased stomatal density, although differences between ambient and elevated CO2 were not significant. High light intensity increased stomatal density compared to low light intensity in both barley varieties and all CO2 treatments. Changes in stomatal conductance were also measured alongside the accumulation of pentoses, hexoses, disaccharides, and abscisic acid detected by liquid chromatography coupled with mass spectrometry. High light increased the accumulation of all sugars and reduced abscisic acid levels. Abscisic acid was influenced by all factors—light, CO2, and genotype—in combination. Differences were discovered between the two barley varieties: oxidative stress sensitive Barke demonstrated higher stomatal density, but lower conductance and better water use efficiency (WUE) than oxidative stress resistant Bojos at saturating light intensity. Barke also showed greater variability between treatments in measurements of stomatal density, sugar accumulation, and abscisic levels, implying that it may be more responsive to environmental drivers influencing water relations in the plant.

This study evaluates drought stress effect on winter wheat. Simultaneously, the ability of the HERMES crop growth model to reproduce the process correctly was tested. The field experiment was conducted at Domanínek station in 2014 and 2015, where mobile rain-out shelters were installed on plots of winter wheat (May 2015). Precipitation was reduced in three replications and the findings were compared with results from control plots with ambient precipitation. A precipitation reduction of 93 mm led to reduced growth and decrease in grain yields. The results of this study showed that the model was able to reproduce soil moisture content well and reproduce the drought stress for crop yields of winter wheat to a certain extent. When rain-out shelters were used, real winter wheat yields were reduced by 1.7 t/ha. The model underestimated the yields for the sheltered variant by 0.67 t/ha on average against observed yields and overestimated development of leaf area for both unsheltered and sheltered variants. This overestimation was partly explained by the effect of excluded UV radiation. The outcome of this paper may help to reduce uncertainty within simulated yields of winter wheat under extreme weather conditions through a better understanding of model behavior.

Tropical forests are biodiversity hotspots, but it is not well understood how this diversity is structured and maintained. One hypothesis rests on the generation of a range of metabolic niches, with varied composition, supporting a high species diversity. Characterizing soil metabolomes can reveal fine-scale differences in composition and potentially help explain variation across these habitats. In particular, little is known about canopy soils, which are unique habitats that are likely to be sources of additional biodiversity and biogeochemical cycling in tropical forests. We studied the effects of diverse tree species and epiphytes on soil metabolomic profiles of forest floor and canopy suspended soils in a French Guianese rainforest. We found that the metabolomic profiles of canopy suspended soils were distinct from those of forest floor soils, differing between epiphyte-associated and non-epiphyte suspended soils, and the metabolomic profiles of suspended soils varied with host tree species, regardless of association with epiphyte. Thus, tree species is a key driver of rainforest suspended soil metabolomics. We found greater abundance of metabolites in suspended soils, particularly in groups associated with plants, such as phenolic compounds, and with metabolic pathways related to amino acids, nucleotides, and energy metabolism, due to the greater relative proportion of tree and epiphyte organic material derived from litter and root exudates, indicating a strong legacy of parent biological material. Our study provides evidence for the role of tree and epiphyte species in canopy soil metabolomic composition and in maintaining the high levels of soil metabolome diversity in this tropical rainforest. It is likely that a wide array of canopy microsite-level environmental conditions, which reflect interactions between trees and epiphytes, increase the microscale diversity in suspended soil metabolomes.

Heat stress around anthesis is considered to have an increasing impact on wheat yield under the ongoing climate change. However, the effect of high temperatures and their duration on formation of individual yield parameters is still little understood. Within this study, the effect of high temperatures applied during anthesis for 3 and 7 days on yield formation parameters was analysed. The study was conducted in growth chambers under four temperature regimes (daily temperature maxima 26, 32, 35 and 38°C). In the periods preceding and following heat stress regimes the plants were cultivated under ambient weather conditions. The number of grains per spike was reduced under temperatures ≥ 35°C in cv. Bohemia and ≥ 38°C in cv. Tobak. This resulted in a similar response of spike productivity. Thousand grain weight showed no response to temperature regime in cv. Tobak, whereas in cv. Bohemia, a peak response to temperature with maximum at 35°C was observed. The duration of heat stress had only little effect on most yield formation parameters.

Light quality modulates plant growth, development, physiology, and metabolism through a series of photoreceptors perceiving light signal and related signaling pathways. Although the partial mechanisms of the responses to light quality are well understood, how plants orchestrate these impacts on the levels of above- and below-ground tissues and molecular, physiological, and morphological processes remains unclear. However, the re-allocation of plant resources can substantially adjust plant tolerance to stress conditions such as reduced water availability. In this study, we investigated in two spring barley genotypes the effect of ultraviolet-A (UV-A), blue, red, and far-red light on morphological, physiological, and metabolic responses in leaves and roots. The plants were grown in growth units where the root system develops on black filter paper, placed in growth chambers. While the growth of above-ground biomass and photosynthetic performance were enhanced mainly by the combined action of red, blue, far-red, and UV-A light, the root growth was stimulated particularly by supplementary far-red light to red light. Exposure of plants to the full light spectrum also stimulates the accumulation of numerous compounds related to stress tolerance such as proline, secondary metabolites with antioxidative functions or jasmonic acid. On the other hand, full light spectrum reduces the accumulation of abscisic acid, which is closely associated with stress responses. Addition of blue light induced accumulation of γ-aminobutyric acid (GABA), sorgolactone, or several secondary metabolites. Because these compounds play important roles as osmolytes, antioxidants, UV screening compounds, or growth regulators, the importance of light quality in stress tolerance is unequivocal.

Tropical plants are expected to have a higher variety of defensive traits, such as a more diverse array of secondary metabolic compounds in response to greater pressures of antagonistic interactions, than their temperate counterparts. We test this hypothesis using advanced metabolomics linked to a novel stoichiometric compound classification to analyze the complete foliar metabolomes of four tropical and four temperate tree species, which were selected so that each subset contained the same amount of phylogenetic diversity and evenness. We then built Bayesian phylogenetic multilevel models to test for tropical–temperate differences in metabolite diversity for the entire metabolome and for four major families of secondary compounds. We found strong evidence supporting that the leaves of tropical tree species have a higher phenolic diversity. The functionally closer group of polyphenolics also showed moderate evidence of higher diversity in tropical species, but there were no differences either for the entire metabolome or for the other major families of compounds analyzed. This supports the interpretation that this tropical–temperate contrast must be related to the functional role of phenolics and polyphenolics.

Barley (Hordeum vulgare) accumulates phenolic compounds (PhCs), which play a key role in plant defense against environmental stressors as antioxidants or UV screening compounds. The influence of light and atmospheric CO2 concentration ([CO2]) on the accumulation and localization of PhCs in barley leaves was examined for two varieties with different tolerances to oxidative stress. PhC localization was visualized in vivo using fluorescence microscopy. Close relationships were found between fluorescence-determined localization of PhCs in barley leaves and PhC content estimated using liquid chromatography coupled with mass spectroscopy detection. Light intensity had the strongest effect on the accumulation of PhCs, but the total PhC content was similar at elevated [CO2], minimizing the differences between high and low light. PhCs localized preferentially near the surfaces of leaves, but under low light, an increasing allocation of PhCs in deeper mesophyll layers was observed. The PhC profile was significantly different between barley varieties. The relatively tolerant variety accumulated significantly more hydroxycinnamic acids, indicating that these PhCs may play a more prominent role in oxidative stress prevention. Our research presents novel evidence that [CO2] modulates the accumulation of PhCs in barley leaves. Mesophyll cells, rather than epidermal cells, were most responsive to environmental stimuli in terms of PhC accumulation.

Abstract Background Non-invasive and high-throughput monitoring of drought in plants from its initiation to visible symptoms is essential to quest drought tolerant varieties. Among the existing methods, chlorophyll a fluorescence (ChlF) imaging has the potential to probe systematic changes in photosynthetic reactions; however, prerequisite of dark-adaptation limits its use for high-throughput screening. Results To improve the throughput monitoring of plants, we have exploited their light-adaptive strategy, and investigated possibilities of measuring ChlF transients under low ambient irradiance. We found that the ChlF transients and associated parameters of two contrasting Arabidopsis thaliana accessions, Rsch and Co, give almost similar information, when measured either after ~20 min dark-adaptation or in the presence of half of the adaptive growth-irradiance. The fluorescence parameters, effective quantum yield of PSII photochemistry (ΦPSII) and fluorescence decrease ratio (R FD) resulting from this approach enabled us to differentiate accessions that is often not possible by well-established dark-adapted fluorescence parameter maximum quantum efficiency of PSII photochemistry (F V/F M). Further, we screened ChlF transients in rosettes of well-watered and drought-stressed six A. thaliana accessions, under half of the adaptive growth-irradiance, without any prior dark-adaptation. Relative water content (RWC) in leaves was also assayed and compared to the ChlF parameters. As expected, the RWC was significantly different in drought-stressed from that in well-watered plants in all the six investigated accessions on day-10 of induced drought; the maximum reduction in the RWC was obtained for Rsch (16%), whereas the minimum reduction was for Co (~7%). Drought induced changes were reflected in several features of ChlF transients; combinatorial images obtained from pattern recognition algorithms, trained on pixels of image sequence, improved the contrast among drought-stressed accessions, and the derived images were well-correlated with their RWC. Conclusions We demonstrate here that ChlF transients and associated parameters measured even in the presence of low ambient irradiance preserved its features comparable to that of measured after dark-adaptation and discriminated the accessions having differential geographical origin; further, in combination with combinatorial image analysis tools, these data may be readily employed for early sensing and mapping effects of drought on plant’s physiology via easy and fully non-invasive means.

Plant root system architecture (RSA) has an important role in crop production, particularly for water and nutrient uptake under limiting conditions. In the last few years, several root phenotyping methods have been developed. Here we present a new technique which has been developed for non-destructive, inexpensive and high-throughput root growth studies and RSA analyses. To illustrate the potential applications, this method was tested in an experiment with nitrogen and phosphorous deficiencies in a nutrient solution, affecting RSA parameters of two spring barley varieties (Bojos and Barke). This technique is based on root growth on vertically positioned black filter paper (30 × 60 cm) placed between two black plastic (PVC-P) foils and micro-irrigation systems providing the recirculation of nutrient solution. The pre-germinated seeds were placed in the slit between two plastic bars which carry the filter paper and plastic sheets and fix the plant in the vertical position. This system allows easy repeated non-invasive access to roots for their measuring and sampling. Eighteen days after transplanting the root imaging was done using an RGB digital camera. To evaluate the root architecture parameters the "SmartRoot" software was used. The results revealed that the system is able to detect changes in RSA which are caused mainly by P deficiency (particularly changes in lateral root length and total root area). It can be concluded that this technique has a great potential for non-destructive root growth studies, RSA measurement and root sampling.

Fertilisation of cereal crops with nitrogen (N) has increased in the last five decades. In particular, the fertilisation of wheat crops increased by nearly one order of magnitude from 1961 to 2010, from 9.84 to 93.8 kg N ha−1 y−1. We hypothesized that this intensification of N fertilisation would increase the content of allergenic proteins in wheat which could likely be associated with the increased pathology of coeliac disease in human populations. An increase in the per capita intake of gliadin proteins, the group of gluten proteins principally responsible for the development of coeliac disease, would be the responsible factor. We conducted a global meta-analysis of available reports that supported our hypothesis: wheat plants growing in soils receiving higher doses of N fertilizer have higher total gluten, total gliadin, α/β-gliadin, γ-gliadin and ω-gliadin contents and higher gliadin transcription in their grain. We thereafter calculated the per capita annual average intake of gliadins from wheat and derived foods and found that it increased from 1961 to 2010 from approximately 2.4 to 3.8 kg y−1 per capita (+1.4 ± 0.18 kg y−1 per capita, mean ± SE), i.e., increased by 58 ± 7.5%. Finally, we found that this increase was positively correlated with the increase in the rates of coeliac disease in all the available studies with temporal series of coeliac disease. The impacts and damage of over-fertilisation have been observed at an environmental scale (e.g., eutrophication and acid rain), but a potential direct effect of over-fertilisation is thus also possible on human health (coeliac disease).

The number of ecometabolomic studies, which use metabolomic analyses to disentangle organisms’ metabolic responses and acclimation to a changing environment, has grown exponentially in recent years. Here, we review the results and conclusions of ecometabolomic studies on the impacts of four main drivers of global change (increasing frequencies of drought episodes, heat stress, increasing atmospheric carbon dioxide (CO2) concentrations and increasing nitrogen (N) loads) on plant metabolism. Ecometabolomic studies of drought effects confirmed findings of previous target studies, in which most changes in metabolism are characterized by increased concentrations of soluble sugars and carbohydrate derivatives and frequently also by elevated concentrations of free amino acids. Secondary metabolites, especially flavonoids and terpenes, also commonly exhibited increased concentrations when drought intensified. Under heat and increasing N loads, soluble amino acids derived from glutamate and glutamine were the most responsive metabolites. Foliar metabolic responses to elevated atmospheric CO2 concentrations were dominated by greater production of monosaccharides and associated synthesis of secondary metabolites, such as terpenes, rather than secondary metabolites synthesized along longer sugar pathways involving N-rich precursor molecules, such as those formed from cyclic amino acids and along the shikimate pathway. We suggest that breeding for crop genotypes tolerant to drought and heat stress should be based on their capacity to increase the concentrations of C-rich compounds more than the concentrations of smaller N-rich molecules, such as amino acids. This could facilitate rapid and efficient stress response by reducing protein catabolism without compromising enzymatic capacity or increasing the requirement for re-transcription and de novo biosynthesis of proteins.

The use of photosystem II (PSII) inhibitors allows simulating cascade of defense and damage responses, including the oxidative stress. In our study, PSII inhibiting herbicide metribuzin was applied to the leaf of the model plant species Chenopodium album. The temporally and spatially resolved cascade of defense responses was studied noninvasively at the leaf level by combining three imaging approaches: Raman spectroscopy as a principal method, corroborated by chlorophyll a fluorescence (ChlF) and infrared thermal imaging. ChlF imaging show time-dependent transport in acropetal direction through veins and increase of area affected by metribuzin and demonstrated the ability to distinguish between fast processes at the level of electron transport (1 − Vj) from slow processes at the level of non-photochemical energy dissipation (NPQ) or maximum efficiency of PSII photochemistry (Fv/Fm). The high-resolution resonance Raman images show zones of local increase of carotenoid signal 72 h after the herbicide application, surrounding the damaged tissue, which points to the activation of defense mechanisms. The shift in the carotenoid band indicates structural changes in carotenoids. Finally, the increase of leaf temperature in the region surrounding the spot of herbicide application and expanding in the direction to the leaf tip proves the metribuzin effect on slow stomata closure.

Retrieving information on the plant physiological status from spectral reflectance is a challenging task in many ways. The easiest way to get the information is through normalized vegetation indices, that are based on a normalization of reflectance in specific wavebands. Beside the most common spectral indices such as Photochemical Reflectance Index PRI or Normalized Difference Vegetation Index NDVI, several new indices has been proposed during the past decade as potential physiological indicators. In this paper, the performance of several of them for determining the physiological status of the foliage is evaluated on an experimental Norway spruce needles (Picea abies (L.) Karst) plot. Four needle classess of 27 years old spruce have been sampled throughout cloudy and sunny day. Needle classes were represented by the needles of the branchlets of the 4th, 7th, 9th and 12th whorls. Study was conducted on one-year old needles and sampling ran over several times a day to separate influence of dynamic processess on parameters. Results show that the ratio of reflectance in the green and red region (presented as ratio of reflectance at 560 nm and 694 nm) outperforms the others examinated vegetation indices, and suggest that it would be best suited for the characterization of the leaf status. Being always the highest in the uppermost part of the crown and the lowest in shaded part of the crown, parameter is strictly stratificated throughout the crown. Furthermore, parameter values correspond with intensity of physiological processess ongoing in needles during midday. The values of the other indicators seem to be affected by leaf pigment content and morphology too much. Neither PRI nor NDVI were able to distinguish differences in needle properties sufficiently.

Hyperspectral reflectance is becoming more frequently used for measuring the functions and productivity of ecosystems. The purpose of this study was to re-evaluate the potential of the photochemical reflectance index (PRI) for evaluating physiological status of plants. This is needed because the reasons for variation in PRI and its relationships to physiological traits remain poorly understood. We examined the relationships between PRI and photosynthetic parameters in evergreen Norway spruce and deciduous European beech grown in controlled conditions during several consecutive periods of 10–12 days between which the irradiance and air temperature were changed stepwise. These regime changes induced significant changes in foliar biochemistry and physiology. The responses of PRI corresponded particularly to alterations in the actual quantum yield of photosystem II photochemistry (ΦPSII). Acclimation responses of both species led to loss of PRI sensitivity to light use efficiency (LUE). The procedure of measuring PRI at multiple irradiance-temperature conditions has been designed also for testing accuracy of ΔPRI in estimating LUE. A correction mechanism of subtracting daily measured PRI from early morning PRI has been performed to account for differences in photosynthetic pigments between irradiance-temperature regimes. Introducing ΔPRI, which provided a better estimate of non-photochemical quenching (NPQ) compared to PRI, also improved the accuracy of LUE estimation. Furthermore, ΔPRI was able to detect the effect of drought, which is poorly observable from PRI.

Mugwort (Artemisia vulgaris L.) extremely spreads on uncultivated agricultural land and expands to arable land. Three sites were chosen in the local area of Uherské Hradiště: field (arable land), balk (adjacent to arable land) and rubble heap (distant from arable land). At each site, 50 plants were selected from which mature achenes were collected in 2002 and 2003. The achenes germinated in a laboratory at a room temperature and were subjected to various germination conditions. A part of them was exposed to the temperature of – 20 °C in a freezer, the other part was stored at a room temperature. The germination was carried out either on filter paper in Petri dishes or in 30 mm layer of siliceous sand. One part of the achenes germinated in daylight, the other part in Petri dishes in the dark. The achenes cultivated in siliceous sand were covered with a 5 mm layer of the sand. The results were statistically assessed using Unistat software, analysis of variance and methods of least significant differences (LSD). Total average germinability of mugwort achenes was 67,7 %. The differences in germinability of frozen (66,7 %) and non-frozen (72,6 %) achenes were not statistically significant. Germinability of the achenes that matured in 2003 (69,9 %) was highly significantly higher than that of the achenes matured in 2002 (65,4 %). The achenes germinated highly significantly more (77,9 %) in daylight as compared with those germinated in the dark (57,4 %). Germinability of the achenes that germinated in siliceous sand was highly significantly higher (70,7 %) than of those that germinated in Petri dishes (64,7 %). Germinability of the achenes matured in the field (64,1 %) was significantly lower in comparison with the germinability of the achenes from a balk (69,7 %) and rubble heap (69,2 %). The results of germinability of the achenes that matured in a rubble heap and balk did not significantly differ.

In 1995-1998, the frequency of selected virulences in the powdery mildew ( Blumeria graminis f. sp. tritici ) population on wheat in the Czech Republic was investigated. Samples of conidia were collected by a mobile version of a spore-trap. A total of 1739 one-colony isolates were analysed on a set of five varieties as differentials. High frequencies (> 50%) were found for virulences Vm2, Vm3a, Vm5 and Vml7, lower frequencies(< 50%) for combinations Vm9,2,1 and Vm2,6 and for Vm4b. There were no significant changes in virulence frequencies except for genes Vm5 and Vm9,2,1 that showed one-year variations. Differences between the eastern part (Moravia) and western part (Bohemia) of the Czech Republic were mostly insignificant for most exam­ ined genes. A significantly higher virulence frequency was found in Moravia for genes Vm3a (in 1995) and Vml7 (in 1996), and in Bohemia for the combination Vm9,2,1 (in 1995). A significant correlation (tested by Kendall's tau B values) existed between Vm2 and Vm5 in 1997 and 1998, and between Vm4b and Vm5 in 1995 and 1998. Values of gametic disequilibrium were also studied. Changes in the complexity of isolate virulence were determined to be small and showed no definite trend.

Environmental factors influence the growth, survival, dissemination and hence the incidence of Fusarium fungi and the disease severity. The knowledge of the quantitative and qualitative effects of environmental factors and growing practices on initial infection, disease development and mycotoxin production is important for prediction of disease severity, yield impact and grain contamination with mycotoxins. The objective of this study was to design a model for prediction of deoxynivalenol (DON) content in winter wheat grain based on weather conditions, preceding crop and soil cultivation. The grain samples from winter wheat field experiments conducted in 2002-2005 to determine the effect of preceding crop in combination with soil cultivation on Fusarium head blight infection were analysed for the DON content. Average daily weather data (temperature, rainfall, relative humidity) were collected using an automated meteorological station and analysed separately for April, May and a 5 days period prior to the beginning of flowering and 5 days after the beginning of flowering. The correlation coefficients of DON content to weather data were calculated for monthly data prior to heading and 5 days data prior to and after the beginning of anthesis. Highest positive correlation coefficients were found for sum of precipitation in April, average temperature in April, and sum of precipitation 5 days prior to anthesis. Significant negative correlation was found for average temperature in May and average relative humidity 5 days prior to anthesis. Using the data from this experiment, we trained neural networks for prediction of deoxynivalenol content on the basis of weather data and preceding crop. The most appropriate neural network model was then coupled with AgriClim model to simulate spatial and temporal variation of DON content in wheat samples for south Moravia and north-east Austria area.