Plant Physiological Traits Research Articles

Crassulacean acid metabolism (CAM) supersedes the turgor loss point (TLP) as an important adaptation across a precipitation gradient, in the genus Clusia.

As future climates continue to change, precipitation deficits are expected to become more severe across tropical ecosystems. As a result, it is important that we identify plant physiological traits that act as adaptations to drought, and determine whether these traits act synergistically or independently of each other. In this study, we assessed the role of three leaf-level putative adaptations to drought: crassulacean acid metabolism (CAM), the turgor loss point (TLPΨ) and water storage hydrenchyma tissue. Using the genus Clusia as a model, we were able to explore the extent to which these leaf physiological traits co-vary, and also how they contribute to species' distributions across a precipitation gradient in Central and South America. We found that CAM is independent of the TLPΨ and hydrenchyma depth in Clusia. In addition, we provide evidence that constitutive CAM is an adaptation to year-long water deficits, whereas facultative CAM appears to be more important for surviving acute dry seasons. Finally, we find that the other leaf traits tested did not correlate with environmental precipitation, suggesting that the reduced transpirational rates associated with CAM obviate the need to adapt the TLPΨ and hydrenchyma depth in this genus.

Genotype-dependent architectural and physiological responses regulate the strategies of two oregano cultivars to water excess and deficiency regimes

Plants can exhibit alternative strategies to cope with water stress regimes by reconfiguring different morphophysiological processes. Nonetheless, the physiological bases that define the response of oregano genotypes to water stress are still poorly understood. A pot experiment in a greenhouse was conducted to evaluate the changes in the configuration of plant architecture and physiological traits and the strategies displayed by two novel oregano cultivars (Origanum vulgare ssp. hirtum ‘Alpa Sumaj FCA-INTA’ and Origanum x majoricum Cambess. ‘Aguanda FCA-INTA’) in response to two water stress regimes (water excess and deficit) in vegetative phenological stages. To do this, water relations and morphological, developmental, and physiological traits were measured. The architectural and physiological responses were dependent upon stressful water regimes and oregano cultivars. Two strategies were found to face water excess regime: Alpa Sumaj remained quiescent whereas Aguanda followed an escape strategy. Biomass production of Alpa Sumaj was halved since physiological and architectural traits were mostly reduced, especially the leaf area. In contrast, Aguanda was more tolerant because of its altered biomass allocation pattern, leading to taller plants with mild reductions of the leaf area and transpiration rate. Therefore, relative water content and biomass yield were preserved. Contrastingly, the strategy to face water deficit regime in both cultivars was dehydration avoidance. All traits were reduced in a similar way, but interesting genotypic differences in water relation traits were observed. Thereby, leaf water potential decrease was highlighted in Alpa Sumaj cultivar, whereas the lessening in transpiration rate as the leaf area is reduced represented the outstanding physiological trait of Aguanda.

Hyperspectral retrieval of leaf physiological traits and their links to ecosystem productivity in grassland monocultures

Plant functional traits are closely associated with key ecological processes and ecosystem functions. Recent studies have demonstrated that plant functional traits, especially physiological traits, can be successfully derived from hyperspectral images. Plant physiological traits are frequently quantified either as area-based content [μg cm−2] or mass-based concentration [mg g−1 or %]. However, it remains unclear whether the two metrics of traits can be quantified using remote sensing approaches. We quantified area- and mass-based foliar physiological traits to compare the prediction accuracy of the two metrics based on leaf spectra using partial least squares regression (PLSR) at a grassland monoculture experiment. These two metrics were then scaled up to canopy traits, respectively, based on leaf area index (LAI) and biomass to test their performance at the canopy level. The canopy physiological traits with high prediction accuracy (R2 ≥ 0.60) were selected for mapping using the unmanned aerial vehicle (UAV)-based UHD185 spectrometer. Biomass and LAI were also estimated and mapped using the PLSR method. The mapped leaf traits (canopy traits divided by the corresponding LAI), were used to explore the relationships between the interspecific and intraspecific variations in leaf physiological traits and ecosystem productivity (i.e., aboveground biomass). The results showed that the retrieval of leaf physiological traits using leaf spectra and canopy spectra or remote sensing was better performed on an area basis rather than a mass basis, especially for the physiological traits related to photosynthesis. Model selection results also indicted that remotely sensed physiological traits (chlorophyll a, chlorophyll b, carotenoid, carbon, nitrogen, and leaf mass per area (LMA)) and their intraspecific variations (coefficient variation (CV) for a single trait and functional richness (FRic) for multiple traits) were significant predictors of community aboveground biomass across grassland monocultures. Our study highlights the potential of hyperspectral images for trait mapping and estimating ecosystem productivity at large scales. Our findings also provide a vital insight for disentangling the links of functional traits and intra- and interspecific trait variations to key ecological processes and functions.

A systemic approach to the quantification of the phenotypic plasticity of plant physiological traits: the multivariate plasticity index.

The phenotype of an individual emerges from the interaction of its genotype with the environment in which it is located. Phenotypic plasticity (PP) is the ability of a specific genotype to present multiple phenotypes in response to the environment. Past and current methods for quantification of PP present limitations, mainly in what constitutes a systemic analysis of multiple traits. This research proposes an integrative index for quantifying and evaluating PP. The multivariate plasticity index (MVPi) was calculated based on the Euclidian distance between scores of a canonical variate analysis. It was evaluated for leaf physiological traits in two cases using Brazilian Cerrado species and sugarcane varieties, grown under diverse environmental conditions. The MVPi was sensitive to plant behaviour from simple to complex genotype-environment interactions and was able to inform coarse and fine changes in PP. It was correlated to biomass allocation, showing agreement between plant organizational levels. The new method proved to be elucidative of plant metabolic changes, mainly by explaining PP as an integrated process and emergent property. We recommend the MVPi method as a tool for analysis of phenotypic plasticity in the context of a systemic evaluation of plant phenotypic traits.

Angiosperms at the edge: Extremity, diversity, and phylogeny.

A hallmark of flowering plants is their ability to invade some of the most extreme and dynamic habitats, including cold and dry biomes, to a far greater extent than other land plants. Recent work has provided insight to the phylogenetic distribution and evolutionary mechanisms which have enabled this success, yet needed is a synthesis of evolutionary perspectives with plant physiological traits, morphology, and genomic diversity. Linking these disparate components will not only lead to better understand the evolutionary parallelism and diversification of plants with these two strategies, but also to provide the framework needed for directing future research. We summarize the primary physiological and structural traits involved in response to cold- and drought stress, outline the phylogenetic distribution of these adaptations, and describe the recurring association of these changes with rapid diversification events that occurred in multiple lineages over the past 15 million years. Across these threefold facets of dry-cold correlation (traits, phylogeny, and time) we stress the contrast between (a) the amazing diversity of solutions flowering plants have developed in the face of extreme environments and (b) a broad correlation between cold and dry adaptations that in some cases may hint at deep common origins.

Integration of UAV data with soil water balance models for evaluation/monitoring of maize water stress

UAV based photogrammetry and 3D mapping are gaining fast and wide applications around the world majorly due to the relatively low-cost advantage it offers in the acquisition of high resolution multispectral acquisitions, compared to Aerophotogrammetry and satellite acquisitions. This research seeks to demonstrate the applicability of UAV photogrammetry visible, multispectral and thermal in investigating some physiological indexes of plants, reflecting plant physiological traits. A maize field in Latina (Italy) was acquired using a Fly Novex drone and with different cameras for the various acquisitions and consequently for different flight heights. The obtained images were processed using different photogrammetric models and a variable number of Ground Control Points (GCPs) for the georeferencing and accuracy assessment as well. Subsequently, by combining hydrological simulation methods and the use of physical indicators of the state of water stress, a method is proposed for predicting crop water consumption. The study conducted on the agricultural land of test site has provided useful results in terms of water savings, with an estimated value of three quarters of the total cubic meters of water needed to bring the land to saturation.

Potential Effect of Horse Manure-green Waste and Olive Pomace-green Waste Composts on Physiology and Yield Of Garlic (Allium sativum L.) and Soil Fertility

The use of composts appears to be a promising strategy to promote plant growth performance and to enhance soil fertility under field conditions. The objective of the present study was to select the best organic amendment able to enhance garlic growth, yield, physiological and biochemical parameters, as well as to improve soil fertility. The experiment was carried out under field conditions using three treatments: Control (C), Compost 1: horse manure-green waste (C1) and Compost 2: olive pomace-green waste (C2). To evaluate the effects of the application of the two composts on garlic growth, soil fertility and plant physiological, biochemical and nutritional traits were measured. The results showed that C1 decreased soil pH compared to the control, while electrical conductivity increased considerably for C2. In addition, nitrogen (N), phosphorus (P), total organic carbon (TOC) were significantly increased in soil for C1 followed by C2. The increase percentages of shoots dry biomass with C1 and C2 compared to the control were 64.9% and 158%, respectively. Moreover, for bulbs yield, the composts C1 and C2 produced 46.5% and 41.9%, respectively. Besides, physiological and biochemical parameters of garlic were improved by C1 and C2 compared to control plants. Moreover, antioxidant enzymes such as PPO and POX, decreased significantly in treated plants. Furthermore, mineral analyses showed that C1 and C2 significantly improved minerals contents in leaves and bulbs compared to the control. The results demonstrate the potential of horse manure-green waste compost for the improvement and optimization of soil fertility and crop productivity. This organic amendment could be an efficient practice and a potential bio-fertilizer to improve growth and development as well as biological agriculture of garlic production.

Salicylic acid and thiourea mitigate the salinity and drought stress on physiological traits governing yield in pearl millet- wheat.

Plant growth is often affected with hampered physiological and cellular functioning due to salinity and drought stress. To assess the effectiveness of plant bioregulators (PBRs) in mitigating abiotic stresses, a double spilt plot field study was conducted with three replications at ICAR-CSSRI, research farm, Nain, Panipat. The study comprised of three deficit irrigation regimes viz., 100, 80 and 60% of crop evapo-transpiration (ETc) (I1, I2 and I3), four levels of irrigation water salinity i.e. 2, 4, 8, 12 dS m−1 (S0, S1, S2 and S3) and two PBRs salicylic acid (SA; G1) and thiourea (TU; G2). Irrigations, as per regimes and salinity, were applied at identified critical stages of wheat and if needed in pearl millet. PBRs were applied as seed priming and foliar sprays at two sensitive stages of respective crops. The trend of plant height, and physiological and biochemical traits was similar under different treatments at both stages, but differed significantly only at reproductive stage. Water deficit caused significant reduction in pearl millet (5.1%) and wheat (6.7%) grain yields. The reduction in grain yield under 8 and 12 dS m−1 was 12.90 and 22.43% in pearl millet and 7.68 and 32.93% in wheat, respectively compared to 2 dS m−1. Application of either SA (G1) or TU (G2) significantly enhanced plant height and grain yield, but magnitude of the increment was higher with SA in pearl millet and with TU in wheat. Application of SA and TU increased grain yield by 14.42 and 12.98 in pearl millet, and 12.90 and 17.36% in wheat, respectively. The plant height, RWC, TC, MI, LP, proline, Fv/Fm and Na/K ratio significantly reduced by salinity stress in pearl millet and both water and salinity stress in wheat. Application of both PBRs proved beneficial to mitigate adverse effect of water deficit and salt stress by significantly improving physiological traits, biochemical traits and ultimately grain yield in both crops.

Quality indices of tomato plant as affected by water stress conditions and chitosan application

Plants show physiological, morphological and chemical responses to microbial, physical or chemical factors which are known as elicitors. Water deficit stress is one of the most important abiotic stresses that affects plant physiological and morphological traits. Chitosan is a natural, less toxic and economical compound that is biodegradable and eco-friendly with various applications in agriculture. The present experiment was carried out to evaluate the effect of pre-harvest foliar application of chitosan on quality indices of tomato plant under different water stress conditions. Tomato (Cv. Rio Grande) plants were subjected chitosan concentrations (0, 50, 100,150 mg L-1) and water stress intervals (3, 6, 9 and 12 days) after 15 days of transplantation. Tomato plants treated with 6 days water stress interval recorded maximum fruit firmness, fruit juice content, total soluble solids, titratable acidity and ascorbic acid content and minimum of fruit juice pH. Similarly, chitosan application @ 100 mg L-1 attained highest fruit firmness, percent juice content, total soluble solid, titratable acidity, ascorbic acid content and minimum fruit juice pH. It is concluded that 100 mg L-1 chitosan application along with 6 days water interval had positive impact on quality indices of tomato. Keywords: Chitin, Chitosan; Drought Stress; Quality; Stress tolerance; Tomato http://dx.doi.org/10.19045/bspab.2020.90143

Enhancing resistance of Sesamum indicum against Alternaria sesami through Bacillus velezensis AR1.

Considerable yield loss and poor quality of sesame seed are attributed to fungal pathogens including Alternaria sesami. The use of agrochemicals and few biocontrol agents have been employed to at least minimize the problem. Thus, this research work was initiated to mitigate the impact of the disease using Bacillus velezensis AR1. A total of four treatments, A. sesami alone, sole fungicide, AR1, and alternate application of AR1 with dithianon (fungicide) were applied with six replications. The results indicate that the sole and alternate application of AR1 with fungicide reduced disease severity to less than 10%. Plant physiological traits also improved due to the plant growth promoting AR1. Induced plant defense-related biochemicals, i.e. total phenolic and flavonoid contents, were maximum in the plant subjected to AR1 and alternate application with a fungicide. In addition, the concentration of leaf amino acid proline was doubled due to AR1 compared to the control. The concentration of the plant growth-regulating hormones gibberellic acid and indole acetic acid (IAA), as well as leaf chlorophyll, total nitrogen and phosphorus contents were also significantly increased by 203.86, 7.79, 0.31 mg gFW-1 , 0.15 and 0.13%, respectively, due to the treatments. Furthermore, postharvest soil chitinase, cellulase and 1,3-β-glucanase activity results indicated the biological control and rapid soil colonization trends of AR1. From these in vitro and in vivo experiment findings, B. velezensis AR1 can be recommended for biological control of plant fungal diseases for environmentally safe and quality crop production. © 2020 Society of Chemical Industry.

Effects of exogenous manganese on its plant growth, subcellular distribution, chemical forms, physiological and biochemical traits in Cleome viscosa L.

Cleome viscosa L. is a promising species for the phytoremediation of Mn-contaminanted soil. To reveal the adaptive mechanisms of species to Mn stress, plant growth, Mn subcellular distribution, Mn chemical forms, and plant physiological and biochemical traits were characterized in plants grown under different concentrations of Mn2+ (0, 1000, 5000, 10000, 15000 and 20000μM). The results showed that C. viscosa plant biomass initially increased and then decreased with rising Mn treatment concentration. C. viscosa plants can accumulate high levels of Mn in roots and leaves, and both the bioconcentration factor (BCF) and the translocation factor (TF) exhibited values higher than one. Mn was primarily retained in the cell wall and soluble fractions. Predominant chemical forms of Mn were pectate and protein, phosphates, and oxalates-integrated Mn. The activities of antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and the contents of proline, soluble sugar, and soluble protein initially increased and then decreased with enhancing Mn treatment concentration, whereas the malondialdehyde (MDA) content simultaneously displayed a gradual increase. Combined, these results indicate that C. viscosa can tolerate Mn-stress conditions by increasing antioxidant enzyme activities and non-enzymatic metabolites contents. In addition, Mn immobilization in the cell wall and soluble fractions, alongside the storage of Mn in low-activity chemical forms are further important mechanisms to cope with high environmental Mn concentration. This study reveals the adaptive mechanisms of plants to Mn stress, and provides a theoretical basis for the use of C. viscosa as a candidate phytoremediation plant for Mn-contaminated soil.

Stronger intra-specific competition aggravates negative effects of drought on the growth of Cunninghamia lanceolata

Plant-plant competition is a dynamic and complicated process that is strongly influenced by abiotic conditions. Drought is a critical threat to forests, particularly to young plantation forests. Temporal changes in competition combined with the effects of drought may dramatically influence the physiological traits of plants. Cunninghamia lanceolata plants exposed to intra-specific competition and no-competition conditions were investigated under two soil water levels (well-watered and drought). Changes in plant-plant competition relationships and nitrogen uptake rates were measured at different harvest times. The effects of drought and plant competition on physiological traits, for example, leaf nitrogen allocation, δ13C, and levels of abscisic acid (ABA), indole acetic acid (IAA) and jasmonic acid (JA), were also explored. Our results indicated that C. lanceolata shifted from intense neighbor competition to facilitation under well-watered conditions, whereas under drought neighbor competition became much stronger at the second harvest compared to the first harvest. Strong competition significantly decreased N uptake under drought. Leaf NH4+, NO3− and N allocation to water-soluble proteins increased under drought at the first harvest, but significantly declined under prolonged drought. Leaf, stem and root starch concentrations were enhanced by drought. However, during prolonged drought, the root starch concentrations, leaf δ13C, leaf ABA and starch content of C. lanceolata were much lower under strong neighbor competition than in no-competition conditions, which demonstrated that the combined effects of drought and strong competition were more harmful to plant growth and survival compared to single effects. Our study demonstrated that drought combined with competition strongly affected the N uptake, N allocation and physiological traits of plants. Intense competition imposed by neighbors is a great threat to the growth and survival of young C. lanceolata plantations under prolonged drought.

Phytoextraction of cobalt (Co)-contaminated soils by sweet alyssum (Lobularia maritima (L.) Desv.) is enhanced by biodegradable chelating agents

Combining biodegradable chelating agents with phytoextraction is an efficient technique to amend metal-contaminated soils, but most studies have addressed remediation efficiency rather than a comprehensive understanding of the interactions among plant stress, metal accumulation, and metal bioavailability. This study aimed to investigate the effects of biodegradable chelating agents on improving the efficiency of phytoextraction for cobalt (Co)-contaminated soil by sweet alyssum (Lobularia maritima (L.)) and to explore the interrelationships among plant stress, Co accumulation, and Co bioavailability. Sweet alyssum (three plants per pot) was grown in pots containing soil with Co added at 0, 40, and 60 mg kg−1, respectively. After 70 days of growth, we added four biodegradable chelating agents (EDDS, NTA, CA, and OA) at various concentrations (0, 2.5, 5.0, and 7.5 mmol kg−1). The plants were harvested after 7 days, and the biomass, reactive oxygen species (ROS) parameters, Co concentrations of the shoot and root, and available Co content in the soil were analyzed. The results demonstrate that chelating agents significantly (p < 0.05) improved the phytoextraction capability of sweet alyssum and influenced plant growth and stress. The capability of EDDS to activate Co was higher than that of other chelating agents at identical concentrations in Co-contaminated soils. Furthermore, we observed that a moderate concentration (40 mg kg−1) of Co could promote plant growth and that high concentrations of Co (60 mg kg−1) and EDDS (7.5 mmol kg−1) cause enhanced stress to plant growth, even resulting in lower shoot Co accumulation than that in the moderate EDDS treatment (5.0 mmol kg−1). The present study demonstrates that the application of EDDS may be a better choice for Co phytoextraction than NTA, CA, and OA; nevertheless, a high concentration of EDDS may enhance the negative effects on plant growth, physiological traits, and Co accumulation.

Extending the range of applicability of the semi-empirical ecosystem flux model PRELES for varying forest types and climate.

Applications of ecosystem flux models on large geographical scales are often limited by model complexity and data availability. Here we calibrated and evaluated a semi-empirical ecosystem flux model, PREdict Light-use efficiency, Evapotranspiration and Soil water (PRELES), for various forest types and climate conditions, based on eddy covariance data from 55 sites. A Bayesian approach was adopted for model calibration and uncertainty quantification. We applied the site-specific calibrations and multisite calibrations to nine plant functional types (PFTs) to obtain the site-specific and PFT-specific parameter vectors for PRELES. A systematically designed cross-validation was implemented to evaluate calibration strategies and the risks in extrapolation. The combination of plant physiological traits and climate patterns generated significant variation in vegetation responses and model parameters across but not within PFTs, implying that applying the model without PFT-specific parameters is risky. But within PFT, the multisite calibrations performed as accurately as the site-specific calibrations in predicting gross primary production (GPP) and evapotranspiration (ET). Moreover, the variations among sites within one PFT could be effectively simulated by simply adjusting the parameter of potential light-use efficiency (LUE), implying significant convergence of simulated vegetation processes within PFT. The hierarchical modelling of PRELES provides a compromise between satellite-driven LUE and physiologically oriented approaches for extrapolating the geographical variation of ecosystem productivity. Although measurement errors of eddy covariance and remotely sensed data propagated a substantial proportion of uncertainty or potential biases, the results illustrated that PRELES could reliably capture daily variations of GPP and ET for contrasting forest types on large geographical scales if PFT-specific parameterizations were applied.

Comparative proteomic analysis reveals that exogenous 6-benzyladenine (6-BA) improves the defense system activity of waterlogged summer maize

BackgroundExogenous 6-benzyladenine (6-BA) could improve leaf defense system activity. In order to better understand the regulation mechanism of exogenous 6-benzyladenine (6-BA) on waterlogged summer maize, three treatments including control (CK), waterlogging at the third leaf stage for 6 days (V3–6), and application of 100 mg dm− 3 6-BA after waterlogging for 6 days (V3–6-B), were employed using summer maize hybrid DengHai 605 (DH605) as the experimental material. We used a labeling liquid chromatography-based quantitative proteomics approach with tandem mass tags to determine the changes in leaf protein abundance level at the tasseling stage.ResultsWaterlogging significantly hindered plant growth and decreased the activities of SOD, POD and CAT. In addition, the activity of LOX was significantly increased after waterlogging. As a result, the content of MDA and H2O2 was significantly increased which incurred serious damages on cell membrane and cellular metabolism of summer maize. And, the leaf emergence rate, plant height and grain yield were significantly decreased by waterlogging. However, application of 6-BA effectively mitigated these adverse effects induced by waterlogging. Compared with V3–6, SOD, POD and CAT activity of V3–6-B were increased by 6.9, 12.4, and 18.5%, LOX were decreased by 13.6%. As a consequence, the contents of MDA and H2O2 in V3–6-B were decreased by 22.1 and 17.2%, respectively, compared to that of V3–6. In addition, the leaf emergence rate, plant height and grain yield were significantly increased by application of 6-BA. Based on proteomics profiling, the proteins involved in protein metabolism, ROS scavenging and fatty acid metabolism were significantly regulated by 6-BA, which suggested that application of 6-BA exaggerated the defensive response of summer maize at proteomic level.ConclusionsThese results demonstrated that 6-BA had contrastive effects on waterlogged summer maize. By regulating key proteins related to ROS scavenging and fatty acid metabolism, 6-BA effectively increased the defense system activity of waterlogged summer maize, then balanced the protein metabolism and improved the plant physiological traits and grain yield.

Quercus leaf extracts display curative effects against Candidatus Liberibacter asiaticus that restore leaf physiological parameters in HLB-affected citrus trees

Citrus greening, also called Huanglongbing (HLB), is one of the most destructive citrus diseases worldwide. It is caused by the fastidious gram-negative α-proteobacteria bacterium Candidatus Liberibacter asiaticus (CLas) and vectored by the Asian citrus psyllid (ACP), Diaphorina citri. Currently, there is no cure for HLB, no compounds have been successful in controlling HLB, and no sustainable management practices have been established for the disease. Thus, searching for alternative citrus greening disease mitigation strategies is considered an urgent priority for a sustainable citrus industry. The aim of this study was to use compounds extracted from oak, Quercus hemisphaerica, and to assess the antibacterial effects of these against CLas-infected citrus plants. The application of aqueous oak leaf extracts showed substantial inhibitory effects against CLas in citrus plants and the activity of genes related to starch. Significant differences were also observed in plant phenotypic and physiological traits after treatments. Citrus plants treated with oak extracts displayed an increase in stomatal conductance, chlorophyll content and nutrient uptake concurrently with a reduction of CLas titer, when compared to citrus plants treated with just water. The information provided from this study suggests a new management treatment program to effectively deal with the HLB disease.

Environmental and physiological controls on diurnal and seasonal patterns of biogenic volatile organic compound emissions from five dominant woody species under field conditions

Biogenic volatile organic compounds (BVOCs) play essential roles in tropospheric chemistry, on both regional and global scales. The emissions of large quantities of species-specific BVOC depend not only on environmental (temperature, T; photosynthetically active radiation, PAR), but also physiological parameters (i.e. net photosynthetic rate, Pn; transpiration rate, Tr; stomatal conductance, gs and intercellular CO2 concentration, Ci). Here, isoprene, monoterpene and sesquiterpene emissions were determined from five dominant mature woody tree species in northern China, which are two evergreen conifers (Pinus tabuliformis and Platycladus orientalis) and three broad-leaved deciduous trees (Quercus variabilis, Populus tomentosa and Robinia pseudoacacia). A dynamic enclosure technique combined with GC-MS was used to sample BVOCs and analyse their fractional composition at daily and annual scales. The diurnal data showed that both isoprene and monoterpene emissions increased with increasing temperature, and reached their maximum emission rates in the peak of growing season for both coniferous and broad-leaved species. The emissions of individual compound within the monoterpenes and sesquiterpenes were statistically correlated with each other for all species. Furthermore, some oxygenated monoterpene emissions were highly correlated to sesquiterpenes in all tree species. Linking BVOC emissions to environmental and leaf physiological parameters exhibited that monoterpene emissions were linearly and positively correlated to the variation of T, PAR, Pn and Tr, while their relationship to gs and Ci is more complex. Collectively, these findings provided important information for improving current model estimations in terms of the linkage between BVOC emissions and plant physiological traits. The data presented in this study can be used to update emission capacity used in models, as this is the first time of reporting BVOC emissions from five dominant species in this region. The whole-year measurement of leaf-level BVOCs can also advance our understanding of seasonal variation in BVOC emissions.

Comparative Transcriptome Analyses of Gene Response to Different Light Conditions of Camellia oleifera Leaf Using Illumina and Single-Molecule Real-Time-Based RNA-Sequencing

Camellia oleifera Abel. is a critical oil tree species. Camellia oil, which is extracted from the seeds, is widely regarded as a premium cooking oil, with the content of oleic acid being over 80%. Light is thought to be one of the largest essential natural components in the regulation of plant developmental processes, and different light qualities can considerably influence plant physiological and phenotypic traits. In this research, we examined the growth and physiological responses of C. oleifera “MIN 43” cultivar plantlets to three different wavelengths of light, containing white, red, and blue light, and we utilized the combination of the PacBio single-molecule real-time (SMRT) and Illumina HiSeq RNA sequencing to obtain the mRNA expression profiles. The results showed that plantlets growing under blue light conditions displayed superior growth performance, including stimulated enhancement of the leaf area, increased leaf number, increased chlorophyll synthesis, and improved photosynthesis. Furthermore, SMAT sequencing created 429,955 reads of inserts, where 406,722 of them were full-length non-chimeric reads, and 131,357 non-redundant isoforms were produced. Abundant differentially expressed genes were found in leaves under different light qualities by RNA-sequencing. Gene expression profiles of actin, dynein, tubulin, defectively organized tributaries 3 (DOT3), and ADP ribosylation factor 5 (ARF5) were associated with the greatest leaf performance occurring under blue light conditions. Moreover, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis identified hundreds of pathways involved in different light conditions. The pathways of the plant circadian rhythm and hormone signal transduction were associated with different light quality responses in C. oleifera. Phytochrome B (PHYB), constitutively photomorphogenic 1 (COP1), long hypocotyl 5 (HY5), auxin/indole-3-acetic acid (AUX/IAA), Gretchen Hagen 3 (GH3), and small auxin-up RNA (SAUR), which were differentially expressed genes involved in these two pathways, play a vital role in responses to different wavelengths of light in C. oleifera. In addition, blue light significantly promotes flavonoid biosynthesis via changing expression of related genes.

Infection with an asymptomatic virus in rice results in a delayed drought response.

Infection of viruses in plants often modifies plant responses to biotic and abiotic stresses. In the present study we examined the effects of Rice tungro spherical virus (RTSV) infection on drought response in rice. RTSV infection delayed the onset of leaf rolling by 1-2 days. During the delay in drought response, plants infected with RTSV showed higher stomatal conductance and less negative leaf water potential under drought than those of uninfected plants, indicating that RTSV-infected leaves were more hydrated. Other growth and physiological traits of plants under drought were not altered by infection with RTSV. An expression analysis of genes for drought response-related transcription factors showed that the expression of OsNAC6 and OsDREB2a was less activated by drought in RTSV-infected plants than in uninfected plants, further suggesting improved water status of the plants due to RTSV infection. RTSV accumulated more in plants under drought than in well-watered plants, indicating the increased susceptibility of rice plants to RTSV infection by drought. Collectively, these results indicated that infection with RTSV can transiently mitigate the influence of drought stress on rice plants by increasing leaf hydration, while drought increased the susceptibility of rice plants to RTSV.

Fluctuated water depth with high nutrient concentrations promote the invasiveness of Wedelia trilobata in Wetland.

The distribution of invasive and native species in wetlands is determined by hydrological conditions; whereas conditions such as water depth fluctuations, variations in the nutrient concentrations are expected to affect the growth and physiological traits of plants. For the assessment of such effects, we conduct greenhouse experiment with three factors; 1) water depth of 5 cm and 15 cm (static and fluctuated); 2) three levels of nutrient concentrations (i) full‐strength Hoagland solution (N1), (ii) ¼‐strength Hoagland solution (N2), and (iii) 1/8‐strength Hoagland solution (N3); and 3) species, invasive Wedelia trilobata (L.) and its congener, native Wedelia chinensis (Osbeck.) under mono and mixed culture. Water depth of 5 cm combined with any of the nutrient treatments significantly restrained the photosynthesis, intracellular CO2 concentration and leaf chlorophyll of both W. trilobata and W. chinensis. Increase in the water depth to 15 cm with low‐nutrient treatment N3 did not sustain the physiological traits of W. chinensis under mono and mixed planting. A great loss was noted in the growth of W. chinensis at 15 cm static and fluctuated water depth with low‐nutrient treatment (N3) and under mixed culture. In addition, water depth fluctuations with both low‐ and high‐nutrient treatments significantly affected the root‐shoot ratio, relative growth rate, and interspecific interaction among these two species. W. trilobata benefited more from competitive interaction index (CII) under fluctuated water depth at 15 cm with high nutrients, and the value of CII was clearly positive. Therefore, higher competitive ability may contribute to the invasiveness of W. trilobata in wetlands.