Duration Of Drought Stress Research Articles

Expression and Functional Identification of SPL6/7/9 Genes under Drought Stress in Sugarbeet Seedlings.

Sugar beet is a significant sugar crop in China, primarily cultivated in arid regions of the north. However, drought often affects sugar beet cultivation, leading to reduced yield and quality. Therefore, understanding the impact of drought on sugar beets and studying their drought tolerance is crucial. Previous research has examined the role of SPL (SQUAMOSA promoter-binding protein-like) transcription factors in plant stress response; however, the precise contribution of SPLs to the drought stress response in sugar beets has yet to be elucidated. In this study, we identified and examined the BvSPL6, BvSPL7, and BvSPL9 genes in sugar beets, investigating their performance during the seedling stage under drought stress. We explored their drought resistance characteristics using bioinformatics, quantitative analysis, physiological experiments, and molecular biology experiments. Drought stress and rehydration treatments were applied to sugar beet seedlings, and the expression levels of BvSPL6, BvSPL7, and BvSPL9 genes in leaves were quantitatively analyzed at 11 different time points to evaluate sugar beets' response and tolerance to drought stress. Results indicated that the expression level of the BvSPL6/9 genes in leaves was upregulated during the mid-stage of drought stress and downregulated during the early and late stages. Additionally, the expression level of the BvSPL7 gene gradually increased with the duration of drought stress. Through analyzing changes in physiological indicators during different time periods of drought stress and rehydration treatment, we speculated that the regulation of BvSPL6/7/9 genes is associated with sugar beet drought resistance and their participation in drought stress response. Furthermore, we cloned the CDS sequences of BvSPL6, BvSPL7, and BvSPL9 genes from sugar beets and conducted sequence alignment with the database to validate the results. Subsequently, we constructed overexpression vectors, named 35S::BvSPL6, 35S::BvSPL7, and 35S::BvSPL9, and introduced them into sugar beets using Agrobacterium-mediated methods. Real-time fluorescence quantitative analysis revealed that the expression levels of BvSPL6/7/9 genes in transgenic sugar beets increased by 40% to 80%. The drought resistance of transgenic sugar beets was significantly enhanced compared with the control group.

Silicon improves the drought tolerance in pepper plants through the induction of secondary metabolites, GA biosynthesis pathway, and suppression of chlorophyll degradation

Drought stress caused by the global climate considerably disturbs plant yield and growth. Here, we explored the putative roles of silicon in repressing drought mechanisms in pepper and the prominent involvement of secondary metabolites, GA pathway, and photosystem II. Our research revealed that the transcript level of the flavonoid biosynthesis-associated genes, including the PAL, 4-CL, CHS, FLS-1, F3H and DFR, progressively induced in the pepper leaves treated with silicon during the drought stress duration. Moreover, the phenolic and flavonoid compounds extensively induced in the pepper plants. Furthermore, the pepper plants markedly inhibited chlorophyll catabolic-allied genes, senescence-related marker gene, and the Rbohs gene. Silicon application also sustained the membrane stability, supported via fewer electrolyte leakage processes and minor, O2– H2O2 and MDA levels during drought. Apart from this, the pepper plants significantly induced the expression level of the photosystem II-related genes, osmoprotectants pathway-associated genes, and antioxidant defense genes. Moreover, the GA biosynthesis genes were prompted, while the ABA signaling and biosynthesis genes were suppressed in the silicon-supplemented plants. These consequences infer that the role of Si supplementation on enhancing drought tolerance could be elucidated through the activation of secondary metabolites, flavonoid biosynthesis, osmoprotectants, GA pathway, the efficiency of PSII, and the suppression of chlorophyll degradation. Our research outcomes unveil new and remarkable characteristics of silicon supplementation and offer a series of candidate targets for improving the tolerance of pepper plants to drought stress.

Impact of Photosynthetic Efficiency on Watermelon Cultivation in the Face of Drought

Water availability is a limiting factor for plant production, especially in Brazilian semi-arid regions. The main aim of the study was to investigate the physiological effects of drought during the fruiting stage of watermelon cultivation. A completely randomized block design with four replications and six treatments varied by the number of lateral drip tapes (1 or 2) and the duration of drought stress (0, 4, and 8 days) was used. The following parameters were evaluated: relative chlorophyll content, relative leaf water content, electrolyte leakage, CO2 assimilation (A), stomatal conductance (gs), internal CO2 concentration, leaf temperature, transpiration (E), water use efficiency (WUE), carboxylation efficiency (CE), yield, thickness, diameter, length, and fruit °brix, at 4 and 8 days of drought. Drought negatively affected photosynthesis, particularly in treatments with a single dripper and 4 days of drought, resulting in reductions of up to 60% in A, 68% in gs, 44% in E, 58% in WUE, and 59% in CE, but did not have a significant effect on watermelon yield after 4 or 8 days of irrigation. It was concluded that drought influences the physiological responses of watermelon plants, mainly in reducing photosynthesis, but does not drastically affect fruit productivity in short periods of stress.

The key pathways for drought tolerance in Cerasus humilis were unveiled through transcriptome analysis.

Drought stress exerts a significant impact on the growth, development, and yield of fruit trees. Cerasus humilis is an endemic drought-resistant fruit tree in northern China. To elucidate the underlying mechanism of drought resistance in C. humilis, comprehensive physiological measurements and transcriptome analysis were conducted on the leaves of C. humilis subjected to 15- or 22-days of drought stress. We identified multiple GO terms and KEGG pathways associated with the drought stress response by performing GO and KEGG analysis on DEGs. Furthermore, through the prediction of transcription factors (TFs) and analysis of their expression levels, we observed differential expression patterns among most members of stress-responsive TF families as the duration of drought stress increased. WGCNA analysis was performed on the transcriptome to identify gene cluster modules that exhibited a strong correlation with the durations of drought. Subsequently, these modules underwent GO and KEGG enrichment analyses. The study revealed that the TF-mediated lignin biosynthesis pathway, along with the plant hormone signal transduction pathway, played a prominent role in responding to drought stress of C. humilis. Gene profiling analysis, qRT-PCR, and determination of phytohormone and lignin contents further supported this hypothesis. The hierarchical gene regulatory network was finally constructed based on DEGs from the aforementioned key enriched pathways to predict the gene regulatory mechanisms in response to stress for C. humilis. The findings from this study provide valuable insights into how C. humilis copes with drought stress while analyzing crucial gene pathways associated with its resistance from a TF perspective. This research is significant for the genetic breeding of economic forests.

Comparison of Morphological, Physiological, and Related Gene Expression Responses to Drought Stress in Five Camellia vietnamensis Cultivars

The main production area of Camellia vietnamensis (C. vietnamensis) is in the low mountain and hilly areas of southern China. The low survival rate of seedlings caused by drought is one of the main obstacles restricting the development of the C. vietnamensis industry. An exploration of the key adaptation mechanism of C. vietnamensis to drought stress is important in order to improve its drought resistance. We conducted a study on the morphological, physiological, biochemical, and drought resistance-related genes of five C. vietnamensis cultivars grown in Hainan province under varying degrees of drought stress. The results indicate that drought stress can lead to a decrease in the relative water content and photosynthetic capacity of C. vietnamensis leaves. Compared with the control, the drought damage index, malondialdehyde, relative electrical conductivity, soluble protein, soluble sugar and proline contents of the five C. vietnamensis cultivars increased with drought-stress duration and degree. With increasing drought-stress intensity, the activity of antioxidant enzymes and the content of related metabolites (total polyphenols, total flavonoids, tea saponins) gradually increased, and the expression levels of phenylpropanoid pathway-related genes (Cv4CL1, CvCAD1, CvCAD2, CvPOX1, CvPOX2, CvPOX3) were upregulated. Based on the results of the drought tolerance coefficients, principal component analysis, and hierarchical cluster analysis, we classified five C. vietnamensis cultivars into drought-tolerant cultivars (‘Haida 1’); moderately drought-tolerant cultivars (‘Haida 4’ and ‘Wanhai 4’); and drought-sensitive cultivars (‘Wanhai 3’ and ‘Wanhai 1’). The results of this study provide a theoretical basis for the promotion and cultivation of C. vietnamensis and the selection of drought-resistant cultivars.

Responses of radial growth to climate change for two dominant artificial coniferous trees

The adaptability of plantation ecosystems to climate change has become an important issue in many drylands worldwide. The plantation forests of the Loess Plateau, one of the driest areas in China, have greatly increased, and Picea crassifolia and Pinus tabuliformis are the dominant artificial coniferous species in this region. However, quantitative evaluations of the responses of radial growth to climate change for these two dominant artificial coniferous trees are rare. In this study, we collected tree-ring sample data from four sampling sites in Huajialing and Chankou in the arid Loess Plateau and analysed the radial growth of two artificial conifers and their climate response characteristics (precipitation, temperature, and standardised precipitation evaporation index (SPEI)) using Pearson correlation and the Climwin model. The results showed that (1) low precipitation during the growing season (April-August) and the resulting drought stress were major growth-limiting factors for plantation forests in the arid Loess Plateau, and this impact increased with the duration of drought stress. (2) P. tabuliformis was more susceptible to drought stress than P. crassifolia, and its soil water content at the 0–200 cm depth was already close to the wilting point. (3) The site conditions of planted areas, including initial planting density, elevation, and stand structure (canopy cover), significantly influenced the response of the same tree species to drought stress. (e.g., P. tabuliformis in high-density and low-elevation areas was more susceptible to drought stress than trees in low-density and high-elevation areas). We concluded that forest managers should select appropriate initial planting densities and altitudes and implement pruning and thinning measures at specific ages (15 years for P. crassifolia and 20 years for P. tabuliformis) based on basal area growth curves. Our results provide valuable information for the sustainable management of plantations against the background of climate warming.

Genome-wide analysis of the NAC gene family and functional verification of the DcNAC043s in Dendrobium catenatum

The NAC (NAM, ATAF1/2 and CUC2) domain protein plays an important role in plant growth and development. The function of members of NAC gene family has been deeply studied in many plants. However, the evolutionary relationships and characteristics of NAC family genes in Dendrobium catenatum (D. candidum) unclear. In this study, we identified 33 NAC genes in D.catenatum, all contain NAM conservative domain. Subcellular localization predictions indicated that all the DcNAC proteins are localized to the nucleus. Phylogenetic analysis suggested that the DcNAC gene family could be divided into four groups. Then, the amino-acid composition, physicochemical properties, gene structure, motif, and promoter cis-acting elements were analyzed, the evolutionarily conservative gene DcNAC043-1 and DcNAC043-2 were found. Using qRT-PCR and phloroglucinol staining experiments, it was demonstrated that DcNAC043s can respond to drought stress in Dendrobium. Within a certain range, the longer the duration of drought stress, the higher the expression level of DcNAC043s, and the stronger the degree of plant lignification. We supplemented the relevant information of NAC gene family in D. catenatum. At the same time, the gene function of DcNAC043s and its contribution to the response of Dendrobium to drought stress were verified. These results provide a comprehensive evolutionary history of NAC genes in D. catenatum, and insight into the biological functions of DcNAC043s genes in response to drought stress.

Proline concentrations in seedlings of woody plants change with drought stress duration and are mediated by seed characteristics: a meta-analysis

Proline accumulation represents one of mechanisms used by plants to prevent the adverse consequences of water stress. The effects of increased proline levels in response to drought differ among species. Trees are exposed to the long-term effects of climate change. The reproductive success of species in a specific environment depends on the functional trait of tree seeds. We conducted a meta-analysis to evaluate the effects of drought stress on the proline concentrations in seedling leaf tissues of woody plant species and their relationships to drought duration, seed mass, seed category and coniferous/deciduous classification. Drought duration exhibited a nonlinear effect on proline accumulations. The drought effect on proline accumulations is greater for deciduous than for coniferous species and is higher for orthodox seed species than for recalcitrant. The seedlings of large-seeded species showed greater effect sizes than those of small-seeded species. Our results suggest that there is an optimum level at which proline accumulations under the influence of drought are the highest. A link between seed functional traits, as well as the coniferous/deciduous classification, and proline concentrations in tree seedlings during water stress were determined for the first time. Proline may help to identify high-quality seeds of trees used for reforestation.

Expression profiling of yield related genes in rice cultivars under terminal drought stress.

Rice crop may experience a significant reduction in yield-up to 50%-due to two occurrences during drought stress: unsuccessful peduncle elongation in panicle exertion and ineffective grain filling. The comprehension of mechanisms that promote drought tolerance during these growth phases is crucial for the production of rice that can withstand drought conditions, thus averting a decrease in crop yield. The expression of two xyloglucan endo transhydrolase/glucosylase genes (OsXTH 5 and 19) in peduncle tissue and a sucrose transporter gene (OsSUT1) in flag leaf sheath were assessed. An experiment was carried out in a factorial arrangement based on completely randomized design in which, factor A was two rice cultivars (Vandana as tolerant and Tarom mahalli as local susceptible to drought) and factor B was five drought stress treatments (full irrigation, drought stress duration in 72 and 96h, re-watering after 120 and 192h). Results showed that expression of OsXTH19 and OsXTH5 genes were upregulated in both Vandana and Tarom mahalli cultivars due to stress treatments. OsXTH19 expression was found to decrease while OsXTH5 expression increased during re-watering treatments. It is likely that the persistence of peduncle growth in the drought-tolerant Vandana cultivar can be attributed to the presence of OsXTH19 under drought conditions and OsXTH5 after re-watering. The expression of OsSUT1 in flag leaf sheath of Vandana in re-watering treatments was reached 8-60-fold re-watering. Peduncle elongation was attributed to two XTH genes under drought stress condition. Panicle exertion may be promoted by sustaining peduncle growth despite drought stress. Consequently, this may led to reduce in non fertile florets and decrease in grain yield by 50%. As grain filling depend to expression of OsSUT1 in flag leaf sheath under drought stress, to improve rice cultivars under aerobic production system and drought stress, it is advised to apply these findings in rice breeding programs.

Effect of Water Stress Duration on the Growth Characteristics and Yield Components of Upland Rice Varieties in Kenya

Drought stress is a major problem in upland rice grown areas under rainfed conditions. It affects plant growth and development, and eventually leads to a considerable yield reduction. The study was carried out with the aim of evaluating the effect of drought stress duration on the growth characteristics and yield components of upland rice varieties. The experiment was conducted at the University of Eldoret with Sixteen upland commercial and local rice varieties were used in the study obtained from Kenya and Liberia. Rice plants were subjected to drought stress treatments at tillering and flowering stages in the green house. The experiment was layout in a complete randomized design (CRD) in a split plot arrangement with five treatments and replicated three times. The results of leaf rolling, plant height, days to 50% flowering, days to maturity, panicle number, spikelet sterility, biological yield, leaf relative water content,1000-grain weight, harvest index and grain yield revealed that there were significant differences as a result of water stress on the treatments (p≤0.001) and rice varieties (p≤0.05). All the sixteen varieties were significantly affected by the treatments when compared with the control. The results also revealed that MWUR, Dourado, L-22, Komboka, Jaowo, LAC-23, Kpatawee, MWUR, White rice and Red Youmo varieties were significantly affected by the water stress treatments at leaf rolling, flowering and maturity then that of NERICA 1,2 ,3, 4, 10,11 and 14 at tillering and flowering stages. The findings of this study indicated that NERICA 1, 2, 3, 4, 10 varieties were less affected by soil water stress treatments amongst the tested varieties, followed by NERICA 11 and14 respectively. Thus, NERICA varieties had the best performance in most of the parameters that were measured. Therefore, these varieties can thus be used by breeders to develop varieties adapted to areas with limited rain fall and insufficient soil moisture for rice production.

Effects of Drought Stress on Non-Structural Carbohydrates in Different Organs of Cunninghamia lanceolata.

The Chinese fir Cunninghamia lanceolata (Lamb.) Hook. is an important timber conifer species in China. Much has been studied about Chinese fir, but the distribution of non-structural carbohydrates (NSCs) among different organs (needles, branch, stem, and roots) under drought stress remains poorly understood. In this study, we used one-year-old C. lanceolata plantlets to evaluate the effects of simulated drought under four water regimes, i.e., adequate water or control, light drought, moderate drought, and severe drought stress corresponding to 80%, 60%, 50%, and 40%, respectively of soil field maximum capacity on various NSCs in the needles, branch, stem and roots. The degree and duration of drought stress had significant effects on fructose, glucose, sucrose, soluble sugar, starch, and NSC content in various organs (p < 0.05). Fructose content increased in stem xylem, stem phloem, and leaves. Glucose and sucrose content declined in stem and branch xylem under light drought stress and moderate drought stress, and increased under severe drought stress conditions. Soluble sugars content declined, and starch content increased in leaf and branch phloem, but the latter could not compensate for soluble sugar consumption in the whole plant, and therefore, total NSCs decreased. Correlation analysis showed that a significant positive correlation existed in the soluble sugar content between leaves and roots, and between xylem and phloem in the stems and branches. Chinese fir appears to have different NSCs distribution strategies in response to drought stress, viz., allocating more soluble sugars to fine roots and increasing starch content in the needles, as well as ensuring osmosis to prevent xylem embolism. Our study may broaden the understanding of the various mechanisms that Chinese fir and other plants have to enhance their tolerance to drought stress.

Effect of changes in soil moisture on agriculture soils: response of microbial community, enzymatic and physiological diversity

Global warming-induced drought stress and the duration of changes in soil moisture content may reshape or complicate these ecological relations. Biological activity could be affected severely by the impact of drought on agricultural ecosystems. In this study, 4 agricultural different soils were collected, and analyzed at each time gradient (0, 1, 2, 4, 8th week) to determine the physicochemical parameters, microbial abundance, enzyme activities (dehydrogenases (DH), phosphatases (acid ACP and alkaline ALP) and urease (UR)), and physiological diversity. We found that soil physicochemical properties fluctuated within the time gradient in all sites, but significantly decreased in total organic carbon, available phosphorus (P2O5 Olsena), nitrate (NO3-), ammonium (NH4+) (except for S site) and calcium carbonate (CaCO3) content (except for L site). Overall, ALP activity was higher compared to ACP activity. The DH activity was highest at sampling day (high moisture content) in G and N sites, and at 2nd week for L and S sites, but significantly decreased at the end of the experiment. The UR activity decreased significantly in G, L and N sites but increased in S site at the end of our experiment compared to the sampling day. Overall, the physiological diversity of the microbial community was strongly affected by water stress in the utilization of carbohydrates, carboxylic and acetic acids, amino acids, polymers, and amines, in all sites. Our findings highlighted that the short-term duration of drought stress had a significant influence on soil biological activity. This may improve the understanding of impact of soil moisture changes on soil nutrient cycling and biological activities in agricultural ecosystems.

Responses of Trollius chinensis to drought stress and rehydration: From photosynthetic physiology to gene expression

Drought stress occurs more frequently in recent years due to the global climate change. Widely distributed in northern China, Mongolia, and Russia, Trollius chinensis Bunge has high medicinal and ornamental values and is often exposed to drought stress, while the mechanism underlying its drought response is still unclear. In this study, we applied 74–76% (control, CK), 49–51% (mild drought), 34–36% (moderate drought), and 19–21% (severe drought, SD) of the soil gravimetric water content to T. chinensis, and measured leaf physiological characteristics on the 0, 5th, 10th, 15th day after the soil reaching the set drought severities, and on the 10th day after rehydration. The results showed that many physiological parameters, such as chlorophyll contents, Fv/Fm, ΦPSⅡ, Pn, and gs decreased with the deepening of severity and duration of drought stress and recovered to some extent after rehydration. On the 10th day of drought stress, leaves in SD and CK were selected for RNA-Seq, and 1649 differentially expressed genes (DEGs) were found, including 548 up-regulated and 1101 down-regulated DEGs. Gene Ontology enrichment found that the DEGs were mainly enriched in catalytic activity and thylakoid. Koyto Encyclopedia of Genes and Genomes enrichment found that DEGs were enriched in some metabolic pathways such as carbon fixation and photosynthesis. Among them, the differential expression of genes related to photosynthesis process, ABA biosynthesis and signaling pathway, such as NCED, SnRK2, PsaD, PsbQ, and PetE, might explain why T. chinensis could tolerate and recover from as long as 15 days of severe drought conditions.

Hydric Behavior: Insights into Primary Metabolites in Leaves and Roots of Cabernet Sauvignon and Grenache Grapevine Varieties under Drought Stress

The classification of grapevine cultivars into isohydric and anisohydric categories depends on their ability to close stomata under conditions of low soil water availability or high atmospheric demand. This study aimed to compare the responses of Grenache, classified as isohydric, and Cabernet Sauvignon, classified as anisohydric, both grafted onto Richter 110 rootstock, and subjected to severe drought stress. Three cycles of drought stress were applied, followed by watering, while a well-watered treatment served as the control. Stomatal conductance and stem water potential were measured at predawn and midday during the drought cycles, and primary metabolites were analyzed in leaves and roots using gas chromatography. We found that Grenache had significantly higher stomatal conductance than Cabernet Sauvignon under both well-watered and water-stressed conditions. There were no significant differences in stem water potential between the two varieties, but the control treatment maintained a higher stem water potential at predawn and midday for both varieties. Primary metabolite analysis showed that both varieties accumulated sugars and polyols in their leaves and roots under drought stress, while organic acids were more abundant in leaves than in roots. Overall, the results suggest that the hydric behavior of grapevines depends on the intensity and duration of drought stress. In this study, both varieties exhibited near-isohydric behavior by regulating stomatal closure under drought stress. The metabolites identified in this study may serve as potential biomarkers of water drought stress in Grenache and Cabernet Sauvignon grapevines under the conditions of this experiment.

The effects of heading time on yield performance and HvGAMYB expression in spring barley subjected to drought

In the lifetime of a plant, flowering is not only an essential part of the reproductive process but also a critical developmental stage that can be vulnerable to environmental stresses. To ensure survival during drought, plants accelerate the flowering process, and this response is known as “drought escape.” HvGAMYB—transcription factor associated, among others, with flowering process and anther development in barley—has also an important role in developmental modification and yield performance in plants subjected to stressed conditions. Due to the fact that information about the mechanisms associated both with the flowering acceleration and the anther or pollen disruption is limited, the exploration of the potential HvGAMYB role in flower development may shed light on pollen and spike morphology formations in plants grown under unfavorable water conditions. The aim of this study was to characterize differences in responses to drought among early- and late-heading barley genotypes. These two subgroups of plants—differentiated in terms of phenology—were analyzed, and traits linked to plant phenotype, physiology, and yield were investigated. In our study, the drought stress reactions of two barley subgroups showed a wide range of diversity in terms of yield performance, anther morphology, chlorophyll fluorescence kinetics, and pollen viability. The studied plants exhibited different yield performances under control and drought conditions. Moreover, the random distribution of genotypes on the biplot showing variability of OJIP parameters in the second developmental point of our investigation revealed that prolonged drought stress caused that among early- and late-heading plants, the studied genotypes exhibited different responses to applied stress conditions. The results of this study also showed that the HvGAMYB expression level was correlated positively with traits associated with lateral spike morphology in the second developmental point of this investigation, which showed that this association occurred only under prolonged drought and highlighted the drought stress duration effect on the HvGAMYB expression level.

Water stress responses of Saba senegalensis provenances during the seedling stage

Saba senegalensis is a multi-purpose liana from sub-Saharan Africa that is under threat from over-exploitation of its fruits and from land degradation and erratic rainfall affecting its regeneration. This research aims to assess survival, growth and dry matter distribution in the responses to water regimes of S. senegalensis seedlings of nine provenances from slightly, moderately and severely dry zones in Burkina Faso. The study parameters were provenance, water regimes and duration of drought stress. A total of 567 seedlings (63 per provenance) were grown using a factorial design. Five months after germination, three water regimes were applied: high, medium and low soil water content, corresponding respectively to 100, 75 and 50% of soil pot capacity. The experiments lasted for 6, 9 and 12 months after water stress began. Survival rates, growth parameters, biomass production, stress tolerance and stress sensitivity indexes were calculated and the data analyzed using a linear mixed model. Drought stress reduced seedling survival and biomass production, while the relative growth rate in collar diameter increased. Concerning the duration of drought stress, the relative growth rate of seedlings in collar diameter decreased and the shoot-to-root ratio increased. After six months under stress, the seedlings had invested more in roots, whereas after nine and twelve months the reverse trend was observed. Furthermore, seedlings from the slightly dry zone produced more biomass when watered under a low soil water content regime, and were more drought-tolerant than those from severely and moderately dry zones. This could indicate that the seedlings originating from these zones are well adapted to growth under severe water stress. For S. senegalensis domestication programs, seedlings originating from the slightly dry zones can be successfully propagated in agroforestry systems where water is a limiting factor.

Leaf-transcriptome profiles of phoebe bournei provide insights into temporal drought stress responses.

Phoebe bournei (Hemsl.) Yang is used as a commercial wood in China and is enlisted as a near-threatened species. Prolonged droughts pose a serious threat to young seedlings (1-2 years old). A transcriptome sequencing approach, together with the measurement of growth parameters and biochemical analyses were used to understand P. bournei's drought responses on 15d, 30d, and 45d of drought stress treatment. The stem and root dry weights decreased significantly with drought stress duration. Activities of antioxidative enzymes i.e., peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) increased significantly with the increase in drought stress duration. A total of 13,274, 15,648, and 9,949 genes were differentially expressed in CKvs15d, CKvs30d, and CKvs45d, respectively. The differential expression analyses showed that photosystem I and II underwent structural changes, chlorophyll biosynthesis, and photosynthesis were reduced. The genes annotated as POD, SOD, and CAT were upregulated in drought-treated leaves as compared to control. Additionally, plant-hormone signal transduction, MAPK signaling-plant, phenylpropanoid biosynthesis, flavonoid biosynthesis, and starch and sucrose metabolism pathways showed large-scale expression changes in major genes. We also found that members of 25 transcription factor families were differentially expressed. Our study presents and discusses these transcriptome signatures. Overall, our findings represent key data for breeding towards drought stress tolerance in P. bournei.

Application Paclobutrazol and Duration of Drought Stress to Flowering Induction in Chokun Orange

Induction of flowering is one of the efforts that can extend the production period of Chokun oranges. This study aims to determine the effect of the dose of paclobutrazol (PBZ), duration of drought stress and the combination of treatments that gives the best results on the Chokun orange (&lt;em&gt;Citrus&lt;/em&gt; sp.). The research design used was randomized complete block design (RCBD), consisting of 3 replications. The treatment in this study was a combination of the dose of PBZ (control, active ingredient 0.75 g plant&lt;sup&gt;-1&lt;/sup&gt; and active ingredient 1.5 g plant&lt;sup&gt;-1&lt;/sup&gt;) and duration of drought stress (control, 1, 2 and 3 weeks). The results show that the application of PBZ and duration of drought stress can induce the flowering of citrus plants as seen from the generative shoot variables with a quadratic model on the equation y = -17.778x&lt;sup&gt;2&lt;/sup&gt; + 31.556x + 26.667 at the optimum dose of 0.89 g plant&lt;sup&gt;-1&lt;/sup&gt; of active ingredient and 1 week of drought. The dry period of 3 weeks gives the best results seen from variables of the number of flowers and number of fruits. In general, the results suggest that the application of PBZ and duration of drought stress can transfer from the vegetative phase to the generative phase which in turn could induce the flowering of citrus plants.

Dehydration stress influences the expression of brevis radix gene family members in sorghum (Sorghum bicolor)

Brevis radix (BRX) constitutes a small gene family in angiosperms. It was first identified in Arabidopsis thaliana where it contributed to cell proliferation and root elongation. New roles of BRX family members in plant developmental processes and abiotic stress tolerance are getting revealed lately. In this study, we have identified six members belonging to the BRX gene family from Sorghum bicolor. Based on similarity analysis, two each of these members were found to be belonging to BRXL1 (Sobic.007G151500, Sobic.002G218600) and BRXL2 (Sobic.006G203200, Sobic.004G270100) classes and one was of BRXL4 (Sobic.001G008400) class. The sixth member (Sobic.006G117900) with a partial amino acid sequence was a pseudogene. All members except Sobic.006G117900 and Sobic.006G203200 had three conserved BRX domains. The number of exons of the members ranged from 3 to 6 and protein length from 313 to 469aa. All proteins had nuclear localization signals in them. Drought stress imposed on M35-1 genotype of sorghum for a duration of 7 days and 14 days brought about observable changes in root morphology. Mean root length per seedling significantly increased in the drought stressed seedlings. Expression analysis of sorghum BRX members using quantitative PCR showed enhanced expression of all members in drought stressed leaf as well as root tissues. While in leaves the expression of all BRX genes were up-regulated as duration of drought stress increased, only Sobic.007G151500 and Sobic.002G218600 showed enhanced expression in 14-day drought in the roots. Members of BRX gene family may be involved in drought tolerance in sorghum.

Improved drought tolerance of EMS mutagenized Alfalfa (Medicago sativa L.) mutants by in vitro screening at germination stage

The objectives of this study were to determine drought tolerant novel mutant of alfalfa (Medicago sativa L.) genotypes by screening EMS mutagenized 340675 M3 seeds at germination stages in the presence of osmotic stress of 35% PEG6000. Root growth assay provided several drought tolerant candidate mutants. Of those, 4 mutants were further evaluated at water deficit conditions applied for 24 days after the first cutting at flowering bud stage. The results revealed that mutants determined as drought tolerant at germination stage were also tolerant to water deficit conditions. Protein content and superoxide dismutase values were found to be higher in all mutants than controls. Ascorbate peroxides, glutton reductase and lipid peroxidase values varied based on the mutant genotype and duration of drought stress. Drought stress significantly changed transcriptional levels of MtP5CS, MtDehyd, MseIF-2, MtRD2 and MsNAC genes. These results indicated that in vitro screening of alfalfa mutant seeds for osmatic tolerance at germination and early seedling growth stages was successfully able to determine the drought tolerant alfalfa mutants which were also tolerant to water deficit conditions after the first cutting at flowering bud stage.