Mild Drought Stress Research Articles

Exploiting High-Throughput Indoor Phenotyping to Characterize the Founders of a Structured B. napus Breeding Population.

Phenotyping is considered a significant bottleneck impeding fast and efficient crop improvement. Similar to many crops, Brassica napus, an internationally important oilseed crop, suffers from low genetic diversity, and will require exploitation of diverse genetic resources to develop locally adapted, high yielding and stress resistant cultivars. A pilot study was completed to assess the feasibility of using indoor high-throughput phenotyping (HTP), semi-automated image processing, and machine learning to capture the phenotypic diversity of agronomically important traits in a diverse B. napus breeding population, SKBnNAM, introduced here for the first time. The experiment comprised 50 spring-type B. napus lines, grown and phenotyped in six replicates under two treatment conditions (control and drought) over 38 days in a LemnaTec Scanalyzer 3D facility. Growth traits including plant height, width, projected leaf area, and estimated biovolume were extracted and derived through processing of RGB and NIR images. Anthesis was automatically and accurately scored (97% accuracy) and the number of flowers per plant and day was approximated alongside relevant canopy traits (width, angle). Further, supervised machine learning was used to predict the total number of raceme branches from flower attributes with 91% accuracy (linear regression and Huber regression algorithms) and to identify mild drought stress, a complex trait which typically has to be empirically scored (0.85 area under the receiver operating characteristic curve, random forest classifier algorithm). The study demonstrates the potential of HTP, image processing and computer vision for effective characterization of agronomic trait diversity in B. napus, although limitations of the platform did create significant variation that limited the utility of the data. However, the results underscore the value of machine learning for phenotyping studies, particularly for complex traits such as drought stress resistance.

干旱胁迫下柳枝稷在露天矿区土壤中的种子萌发和生长特性

PDF HTML阅读 XML下载 导出引用 引用提醒 干旱胁迫下柳枝稷在露天矿区土壤中的种子萌发和生长特性 DOI: 10.5846/stxb202107091854 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2016YFC0501108）；国家能源集团科技创新项目（HT（2020）2337号）；国家重点研发计划项目（2016YFC0503604） Effect of drought stress on the seed germination and growth characteristics of switchgrass Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:将能源植物用作矿区生态修复物种，对矿区的经济发展和生态环境具有重要意义。以能源植物柳枝稷为研究对象，通过盆栽试验，分析其在对照、轻度、中度以及重度干旱胁迫下柳枝稷幼苗在矿区土壤基质和非矿区土壤基质下的生长特性，并结合不同干旱胁迫下矿区土壤基质中种子萌发特征，揭示柳枝稷对干旱胁迫的响应机制和对矿区土壤的生态适应性。试验结果表明：（1）柳枝稷种子发芽总数、发芽率、发芽势以及发芽指数在轻度胁迫下达到最大值，活力指数在对照组最高，而在重度胁迫下，各项指标均达到最小值；种苗各生长指标在轻度胁迫下最小，幼苗根长和鲜重在重度胁迫下最高，芽长和芽重在其余三组胁迫下相差不大。（2）干旱胁迫使两种土壤基质下的柳枝稷株高降低，枯叶率增加，在对照、轻度胁迫和重度胁迫下能够保持叶片水分含量和分蘖数稳定；矿区土壤基质中，柳枝稷根体积在轻度胁迫下最大，中度胁迫下根长最长，重度胁迫下根数最多；根冠比随着干旱胁迫的加剧表现出先减后增的趋势，在轻度胁迫下最小，在重度胁迫下最大。（3）与非矿区土壤基质相比，柳枝稷在矿区土壤基质下根冠比更大，其余生长指标均更小；随着干旱胁迫的加剧，柳枝稷在矿区土壤基质下的株高、枯叶率、叶片相对含水量以及分蘖数与非矿区土壤基质下变化趋势一致。综上，柳枝稷在矿区土壤下的生长特性比在非矿区土壤下表现更差；在轻度干旱胁迫下各项生理指标表现更好，在中度和重度干旱胁迫下虽然其生长发育受到限制，但能通过调整生物量配比确保自身存活。因此，柳枝稷在矿区土壤环境下具有一定的抗旱性和抗贫瘠性，将其作为矿区生态修复品种具有可行性。 Abstract:Energy plant as one species for ecological restoration in mining areas is of great significance to the economic development and ecological environment of mining areas. Taking switchgrass, an energy plant, as the research object, through pot experiments, by analyzing the growth characteristics of seedlings in the soil matrix of the mining area and the non-mining area under the control, mild, moderate and severe drought stress, combining the seed germination characteristics in the soil matrix of the mining area, the response mechanism of switchgrass to drought stress and the ecological adaptability of the mining area soil were revealed. The test results showed that:(1) the total number of germinations, germination rate, germination potential and germination index of switchgrass seeds reached the maximum under mild stress, and the vitality index was the highest in the control group. Each index reached the minimum under severe stress. Each growth index of seedlings was minimal under mild stress, the root length and fresh weight of seedlings were the highest under severe stress, and the bud length and shoot weight were not much different under the other three groups of stress. (2) Drought stress reduced the plant height of switchgrass under the two soil substrates, and increased the rate of dead leaves. It could maintain the leaf relative water content and the number of tillers stable under the control, mild and severe stresses. In the soil matrix of the mining area, the root volume of switchgrass was the largest under mild stress, the longest root length under moderate stress, and the largest number of roots under severe stress. The root-shoot ratio showed a trend of first decrease and then increase with the intensification of drought stress, reaching the minimum value under mild stress and the maximum value under severe stress. (3) Compared with the soil substrate in the non-mining area, the root-to-shoot ratio of switchgrass under the soil substrate in the mining area was larger, and the other growth indicators were smaller. With the intensification of drought stress, the plant height, dead leaf rate, relative leaf water content and tiller number of switchgrass under the soil matrix in the mining area were consistent with those in the soil matrix in the non-mining area. In summary, the growth characteristics of switchgrass in mining soils were worse than those in non-mining soils. Physiological indicators performed better under mild drought stress, while the growth of switchgrass was restricted under moderate and severe drought stress. In arid and barren environments, switchgrass can ensure its own survival by adjusting the biomass ratio. Therefore, switchgrass had certain resistance to drought and barrenness and was feasible to use it as a variety of ecological restoration in the mining area. 参考文献 相似文献 引证文献

不同水分条件下杨树-玉米复合系统凋落物分解特性

PDF HTML阅读 XML下载 导出引用 引用提醒 不同水分条件下杨树-玉米复合系统凋落物分解特性 DOI: 10.5846/stxb202104060884 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31960245）；甘肃农业大学公招博士科研启动基金项目（GAU-KYQD-2018-07）；甘肃农业大学学科建设基金项目（GAU-XKJS-2018-108，GAU-XKJS-2018-104） Litter decomposition characteristics of poplar-maize agroforestry system under different water conditions Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探讨水分变化对农林复合生态系统凋落物分解特性的影响，以河西走廊杨树（Populus）-玉米（Zea mays）凋落物为研究对象，设置正常水分（9200 m3/hm2，对照），轻度干旱胁迫（减少15%，7800 m3/hm2），中度干旱胁迫（减少30%，6400 m3/hm2）3种不同水分处理条件，采用分解袋法研究了不同水分条件下杨树叶和玉米秸秆的质量残留率、分解速率和养分含量变化特征。结果表明：（1）随着干旱胁迫的加剧，两种凋落物的质量残留率均增加，而分解速率降低。经过164 d的分解后，杨树叶和玉米秸秆的质量残留率分别为70.43%-77.49%、63.55%-68.29%。分析表明：水分和时间对各类型凋落物的质量残留率均有极显著的影响（P<0.001），但二者的交互作用不显著（P>0.05）；干旱胁迫显著降低了玉米秸秆的分解速率，但杨树叶的分解速率却只是在中度干旱胁迫下显著降低（P<0.05）。对于不同类型凋落物而言，分解速率表现为玉米秸秆>杨树叶。（2）两种类型凋落物的氮（N）残留率在分解过程中表现为降低的趋势，但随着干旱程度的加大，N的残留率增加，表明水分抑制了N的释放过程。分解164d后，同一类型凋落物不同水分条件下的N残留率均存在显著差异。对于同一水分条件下不同凋落物而言，玉米秸秆的N残留率最低，而杨树叶最高。总的来说，水分降低对干旱区农林复合系统内凋落物的分解和氮元素含量具有显著的抑制作用。 Abstract:Litter decomposition plays an important role in the carbon budget and nutrient cycling in terrestrial ecosystems, but the decomposition process and decomposition rate of litters were affected by environmental factors, especially the water condition. However, little attention has been paid to the effect of changing water condition at litter decomposition for the maize-poplar system in arid regions. Here the litters of poplar leaves and maize straws in the Hexi Corridor were selected as research objects, and there were three water treatments including normal water (9200 m3/hm2, CK), mild drought stress (irrigation reduced by 15%, 7800 m3/hm2), moderate drought stress(irrigation reduced by 30%, 6400 m3/hm2), which were designed in our experiment. The mass remaining, decomposition rate and nitrogen content for poplar leaves and maize straws were measured and analyzed under different water conditions using decomposing bag method, meanwhile the effects of water changes on the decomposition characteristics of two litter types were analyzed. The results showed that:(1) the mass remaining for two litter types were increasing with increasing drought stress, but the decomposition rates were decreasing. After 164 days of decomposition, the mass remaining for poplar leaves and maize straws litter were 70.43%-77.49%, 63.55%-68.29% under three water conditions, respectively. The analysis indicated that water and time extremely significant affected the mass remaining (P<0.001), but their interactive effects on mass remaining were not significant (P>0.05). Drought stress significantly reduced the decompoation rate of maize straws, but it was only significantly decreased under moderate drought stress for poplar leaves. For the different litter types, the decomposition rate of maize straw was higher than that of poplar leaf. (2) The N remaining of two litter types was decreasing trends in the decomposition process under three water conditions, this showed that the N remaining presented releasing mode in the study period, but the N remaining was increasing with increasing drought stress, it indicated that water reducing significantly inhibited the release process of N for the two litter types. After 164 days of decomposition, the N remaining had significant difference under three water conditions for the same litter, and the decomposition time also extremely significant affected N remaining, but the two interaction has no significant effect on N remaining. For the different litter types, the N remaining for maize straws was minimum and it was maximum for poplar leaves in the same water condition, this showed the N release of poplar leaf was greater than that of maize straw. As a whole, water reducing significantly inhibited the litter decomposition and N release for the two litter types in the agroforestry system in the arid region. 参考文献 相似文献 引证文献

Salicylic acid mitigates the effects of mild drought stress on radish (Raphanus sativus) growth.

Water deficit is the most critical factor limiting plant growth and production and salicylic acid (SA) has potential for stress mitigation in plants; therefore, we evaluated the effect of SA on radish (Raphanus sativus L.) growth and ecophysiology under water deficit. Plants were sprayed with SA (100μM) or water (control), and irrigated at 80% (W80), 60% (W60), 40% (W40), and 20% (W20) of field capacity. The SA treatments and drought stress started 7days after sowing and lasted until the end of the cycle (30days after sowing). The morphophysiological analyses showed that radish plants had impaired growth at the lower water supply levels, but the treatment with SA reversed these growth restraints under moderate stress, leading to increases in shoot mass at W40 and storage root mass at W60 and W40. SA treatment also reversed the reduction of storage root volume at W60. The tendency of water deficit to increase F O and reduce F V /F M suggests possible damage to the photosystem II of drought-stressed plants. The parameters of gas exchange and photosynthetic pigments showed maintained photosynthetic efficiency, but total photosynthesis decreased due the lower shoot dry mass. Overall, exogenously applied SA reversed the growth restraints at W60 and W40, which revealed that SA was effective in mitigating the effects of moderate water deficit on biomass accumulation and partitioning in radish plants.

Exogenous salicylic acid-induced drought stress tolerance in wheat (Triticum aestivum L.) grown under hydroponic culture.

Wheat is an important cereal crop, which is adversely affected by water deficit stress. The effect of induced stress can be reduced by the application of salicylic acid (SA). With the objective to combat drought stress in wheat, an experiment was conducted in greenhouse under hydroponic conditions. The treatments consisted of (a) no drought (DD0 = 0 MPa), mild drought (DD1 = -0.40 MPa) and severe drought (DD2 = -0.60 MPa) by applying PEG-8000, (b) two contrasting wheat varieties Barani-17 (drought tolerant) and Anaj-17 (drought-sensitive), and (c) foliar treatments of salicylic acid (0, 50 mM, 75 mM, and 100 mM). Evaluation of wheat plants regarding biochemical, physiological, and morphological attributes were rendered after harvesting of plants. Statistically, maximum shoot and root fresh and dry weights (18.77, 11.15 and 1.99, 1.81 g, respectively) were recorded in cultivar Barani-17 under no drought condition with the application of SA (100 mM). While, minimum shoot and root fresh and dry weights (6.65, 3.14 and 0.73, 0.61 g, respectively) were recorded in cultivar Anaj-2017 under mild drought stress without SA application. The maximum shoot length (68.0 cm) was observed in cultivar Barani-2017 under no drought condition with the application of SA (100 mM). While, maximum root length (59.67 cm) was recorded in cultivar Anaj-17 under moderate drought stress without application of SA. Further, minimum shoot length (28.67 cm) was recorded in Anaj-17 under moderate drought stress without SA application. Minimum root length (38.67 cm) was recorded in cultivar Barani-17 under no drought condition without SA application. Furthermore, maximum physio-biochemical traits, including membrane stability index (MSI), chlorophyl content, photosynthetic rates, stomatal conductance, antioxidant enzymatic activities and relative water content (RWC) were found highest in cultivar Barani-17 under no drought stress and SA application at 100 mM. However, minimum values of these traits were recorded in cultivar Anaj-17 under severe drought stress without SA application. Our results also demonstrated that under severe drought, application of SA at 100 mM significantly increased leaf nitrogen (N), phosphrus (P) and potassium (K) contents and cultivar Barani-17 demonstrated significantly higher values than Anaj-17. The obtained results also indicated that the cultivation of wheat under drought stress conditions noticeably declines the morphological, physiological, and biochemical attributes of the plants. However, the exogenous application of SA had a positive impact on wheat crop for enhancing its productivity.

Relationship Between Soil Moisture Content and Superoxide Dismutase Activity in Soybean Leaves in Northeast China

Soybean is a crucial source of plant protein and oil; However, a decline in yield has been observed. In this study, spring soybean varieties (Heinong 44 and Heinong 65) were selected to determine the effects of different soil moisture levels on changes in superoxide dismutase (SOD) enzyme activity. A water-cut treatment was conducted on potted soybean plants from the beginning of their flowering stage. The soil moisture content under different water-cut days was recorded, and the SOD activity of soybean leaves was determined. The results showed that the SOD activity of soybean leaves first increased and then decreased with a decrease in soil relative water content. The SOD activity under moderate drought stress was significantly higher than that under suitable water and mild drought conditions, and there was no significant difference between suitable water and mild drought conditions. The relationship between soil moisture content and SOD activity of the two soybean varieties was consistent with the Gaussian curve. When the relative soil moisture content was 34.7%–49.8%, the SOD activity was higher than that under suitable water and mild drought stress conditions. The SOD activity of soybean leaves was highest when the relative soil water content was 42.1%–42.8% under moderate drought stress. This research provides a theoretical basis for the rapid diagnosis of soybean drought stress.

Genetic progress in physiological and biochemical traits related to grain yield in Moroccan durum wheat varieties from 1984 to 2007

AbstractKnowledge of the key physiological and biochemical traits related to genetic progress is essential to identify yield‐limiting factors and guide future breeding strategies. The aim of this research was to determine the rate of genetic gain in grain yield and physiological and biochemical traits in Moroccan durum wheat cultivars released from 1984 to 2007. Plants were subjected to two water regimes (irrigated and rainfed) during three growing seasons in order to identify those physiological and biochemical traits associated with grain yield. Grain yield (GY) and diverse physiological and biochemical traits known to be linked to mild drought stress were evaluated at anthesis and postanthesis. Physiological traits included stomatal conductance (gs), transpiration rate (E), chlorophyll fluorescence (Fv/Fm), chlorophyll content in flag leaf (SPAD), canopy temperature depression (CTD), and relative water content (RWC), whereas biochemical characteristics were leaf proline and water‐soluble carbohydrates (WSC) content. Grain yield tends to increase linearly under irrigated conditions with a genetic gain of 1.75% yr−1, in contrast, no significant change was observed under rainfed conditions. Traits that significantly increased over time were leaf proline content, gs, E, CTD, and SPAD. The changes in GY under irrigated conditions were largely explained by increases in gs during anthesis and postanthesis, CTD at postanthesis, and by leaf proline content at anthesis. Although genetic gains in GY under rainfed conditions could not be detected, leaf proline content and E were strongly associated to GY under these conditions, suggesting their usefulness as selection criteria for GY in water‐limited environments.

English plantain deploys stress tolerance mechanisms at various organization levels across an altitudinal gradient in the Pyrenees.

High-mountain plants must withstand high solar irradiation and low temperatures during winter. Furthermore, climate change is increasing drought events, which pose an additional threat to plants. Here, we studied the stress tolerance mechanisms at various levels of biological organization in English plantain (Plantago lanceolata L.), focusing on photoprotective and antioxidant responses. The response of populations from three different altitudes in the Eastern Pyrenees (1030, 1380, and 1660 m. a.s.l.) was compared during both autumn and winter. Results showed that plants not only suffered from photoinhibition due to very low temperatures at the highest elevation during winter, but also from mild drought stress at the lowest altitude during autumn. Individuals growing at the highest elevation showed reductions in the maximum photochemical efficiency of PSII (Fv /Fm ratio), which might be caused by the lack of an increased induction of tolerance mechanisms at the highest elevation compared to the intermediate one. Although most leaves died at the highest elevation, plants could withstand stress at the organism level by generating new leaves once the stress ceased. Drought at the lowest elevation during autumn caused mild stress with small decreases in the Fv /Fm ratio, along with an increase in abscisic acid and jasmonic acid content. This study underlines the great capacity of English plantain to adapt to high elevation by activating not only photo- and antioxidant protection mechanisms and adjustments in stress-related phytohormones, but also by fully regenerating its aboveground biomass through renewed growth once the stress has ceased.

Assessment of biochemical compounds and antioxidant enzyme activity in barley and wheatgrass under water-deficit condition.

Wheatgrass and barley grass are freshly sprouted leaves of wheat and barley seeds and are rich sources of phytochemicals. This study was conducted to investigate the effects of drought stress on the biochemical compounds and antioxidant activities of barley grass and wheatgrass extracts. The grass was cultivated in an organic soil growing medium with different levels of drought stress (a control with 100% water holding capacity (WHC), mild drought stress with 75% WHC, moderate drought stress with 50% WHC, and severe drought stress with 25% WHC) in a growth chamber by controlling temperature (20/15 °C, day/night), light (12/12 h, light/dark; intensity 150 μmol m-2 s-1 with quantum dot light-emitting diodes), and relative humidity (60%) for 7 days. The drought stress showed increased levels of biochemical compounds, especially phenolics, flavonoids, and vitamin C, in both barley grass and wheatgrass extracts. The wheatgrass extracts showed 1.38-1.67 times higher phenolics, flavonoids, and vitamin C contents than the barley grass extracts did. The antioxidant (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity, and nitrite-scavenging activity) and antioxidant enzymes (guaiacol peroxidase, catalase, and glutathione reductase) were the highest under severe drought stress in both barley grass and wheatgrass extracts; and the wheatgrass extracts showed 1.20-5.70 times higher antioxidant enzyme activities than the barley grass extracts did. Proper drought-stress treatment of barley grass and wheatgrass may be a convenient and efficient method to increase biochemical compounds and antioxidants in our diet to exploit the related health benefits. © 2021 Society of Chemical Industry.

The Role of Nano-Silicon and Other Soil Conditioners in Improving Physiology and Yield of Drought Stressed Barley Crop

Abstract A field experiment was conducted in sandy soil to assess the effect of different sources of soil conditioners on barley (Hordeum vulgare L. cv. Giza 137) growth and its yield under drought stress. Plants were exposed to two levels of drought stress until grain maturity: (A) drought at 75% available water (AW) with NPK as control (treatment, T1); (B) mild drought stress at 50% AW with foliar spray of nano-silicon at 75 ppm (treatment, T2), foliar spray of nano-zeolite at 75 ppm (treatment, T3), perlite at 4 tons/h (treatment, T4), natural zeolite at 600 kg/ha (treatment, T5), bentonite at 4 tons/h (treatment, T6), and a combined treatment of T2+T3+T4+T5+T6 at the half amount of each material (T7). All the treatments received the recommended doses of organic matter. Vegetative growth and yield characters as well as anatomical characters were recorded. The physical and chemical soil properties were significantly improved by both foliar and soil conditioners application. The nutrients content of the barley crop were augmented under combined treatment (T7) as compared to other treatments. Under that treatment, barley crop chemical components, i.e. protein, ash, chlorophylls, amino acids, vitamins, and fibre were significantly higher compared to other treatments. In addition, gibberellic acid (GA3) and abscisic acid (ABA) content besides antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD) activities were significantly affected by all treatments. The economical profits were achieved, as reflected by an investment factor value equal to or higher than 3, and this was achieved for all tested nanosilicon, zeolite, and soil conditioners indicated the effectiveness and profitability of studied treatments.

Physiological Mechanism of Drought-Resistant Rice Coping With Drought Stress

Drought stress is one of the major threats to rice production. The weakening of leaf photosynthesis due to drought is the main reason for the reduction of grain yield, but its mechanism is still obscure. The objectives of this study were to reveal the physiological mechanism of drought stress affecting photosynthetic capacity and grain yield. Pot experiments were conducted with drought-tolerant cultivars Hanyou113 (HY113) and Zhonghan3 (ZH3) and drought-sensitive cultivar Huanghuazhan (HHZ) under four water management treatments (traditional flooding (CK), mild drought stress (LD), moderate drought stress (MD) and severe drought stress (HD)) at heading stage in 2013 and 2014. Compared with CK, grain yield was significantly reduced by 14.9%, 30.8%, and 12.8% in HY113, HHZ, and ZH3 under LD, 32.9%, 33.7%, and 22.9% in HY113, HHZ and ZH3 under MD and 53.6%, 45.6%, and 30.7% in HY113, HHZ, and ZH3 under HD, respectively. The photosynthetic rate (Pn) decreased by 49.0% from 20.0 to 10.2 µmol m−2 s−1 in HY113, and 67.6% from 23.4 to 7.58 µmol m−2 s−1 in HHZ, and 39.3% from 23.4 to 14.2 µmol m−2 s−1 in ZH3 under HD. The Pn of HHZ was similar to that of ZH3 under CK conditions. During the drought periods from LD to HD at heading stage, the leaf water potential (LWP) reduced 31.9%, 54.8%, and 15.7% in HY113, HHZ, and ZH3, respectively. The non-photochemical quenching (NPQ) of HY113, HHZ, and ZH3 flag leaves increased by 150%, 97.6%, and 218%, respectively. The effective quantum yield of PSII photochemistry (ΦPSII) of flag leaves reduced by 20.3%, 11.9%, and 22.1% in HY113, HHZ, and ZH3, respectively. The enzymatic activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) increased by 11.4%, 18.0%, and 21.8% in HY113, and 13.2%, 14.3%, and 30.9% in HHZ, and 13.4% 21.7%, and 17.6% in ZH3 under MD on average across two seasons. The yield reduction of drought-resistant cultivars (HY113, ZH3) was smaller than that of conventional cultivars (HHZ). Maintaining leaf water potential (LWP), Pn, photosystem II (PSII) original light energy conversion efficiency, non–photochemical quenching coefficient (NPQ), and increasing in the ratio of photochemical reaction energy in fluorescence and antioxidant enzyme activity is the physiological basis to achieve a relatively high photosynthesis. These traits could be the target for breeder to develop drought-tolerant varieties.

Transcriptomic analyses provide new insights into jujube fruit quality affected by water deficit stress

Water availability is a crucial factor affecting fruit quality and productivity. A period of mild drought stress can increase fruit sweetness and improve fruit quality. However, the mechanism underlying the transcriptional regulation in Chinese jujube under water deficit conditions remains relatively uncharacterized. In this study, we analyzed the protein and sugar contents, the average weight, and transcript expression (RNA sequencing) of jujube fruit at different ripening stages (i.e., white mature and half-red fruit) under mild and severe water deficit conditions. The sucrose and protein contents increased significantly under water deficit conditions. The increase in water deficit stress from mild to severe did not significantly alter the sugar accumulation, but it decreased the average fruit weight. The sugar- and amino acid-related pathways, flavonoid biosynthesis, xyloglucan metabolism, and phenylpropanoid biosynthesis were affected by water deficit stress. Gene co-expression analyses identified many ABA- and ethylene-related genes with expression levels modulated by water deficit conditions, especially in the half-red stage. Additionally, we identified the key genes affecting fruit sugars, pigments, cell wall polysaccharides, and phenylpropanoids, which influence fruit quality. Notably, genes related to sugar transporters rather than sugar metabolism contributed to the sucrose accumulation. Flavonoid synthesis-related gene expression contributed to the earlier coloration of the stressed fruit than of the control fruit. Severe water deficit stress up-regulated the expression of pectinesterase and endotransglucosylase/hydrolase genes, which accelerated fruit ripening and softening. Regarding the phenylpropanoid biosynthesis pathway, the exposure to mild water deficit stress promoted the synthesis of secondary metabolites useful to humans (e.g., coniferin and syringin), whereas the severe water deficit treatment increased lignin accumulation. Considered together, these findings revealed the transcriptional regulatory mechanism that improved jujube fruit quality under mild drought conditions. Furthermore, the results of this study may be useful for optimizing the irrigation during jujube cultivation.

Drought Stress Alleviation by Potassium-Nitrate-Containing Chitosan/Montmorillonite Microparticles Confers Changes in Spinacia oleracea L.

Drought and low amounts of mineral nutrients in the soil are the two leading global constraints in arid and semiarid regions. Their detrimental effects on soils and crops can be alleviated by applying controlled release and biodegradable fertilizers to better and sustain the crops. On a global scale, spinach (Spinacia oleracea L.) is an essential leafy green vegetable that is biologically considered a reliable source of essential nutrients and minerals for human health. A comprehensive approach is needed to manage water stress to mitigate the impacts of stress-caused damage and to examine this for better and increased plant production. An experiment was conducted using potassium-nitrate-containing chitosan/montmorillonite microparticles (150 mg) under mild and severe drought stress (MDS: 50% and SDS: 35% FC, respectively). The treatments include control (no KNO3 and 70% FC as normal irrigation (NI)), KNO3 + NI, 50% FC as mild drought stress (MDS), KNO3 + MDS, 35% FC as severe drought stress (SDS) and KNO3 + SDS. Results revealed that drought stress decreased all studied physiological parameters and increased oxidative stress indicators in spinach. Applying KN significantly increased root (122%) and shoot length (4%), shoot fresh weight (32%) and shoot dry weight (71%), chlorophyll a (88%), carotenoids (39%), total soluble proteins (50%), soluble sugars (51%), potassium (80%), and phosphorous (32%) concentrations over No KN at severe drought. While stress indicators, like glycine betaine, malondialdehyde, hydrogen peroxide, electrolyte leakage, peroxidase, superoxide dismutase, and ascorbic acid levels, were increased in stress. Treatment KN was proved efficient and effective in improving spinach physiological status in both MDS and SDS.

Elevated [CO2] Mitigates Drought Effects and Increases Leaf 5-O-Caffeoylquinic Acid and Caffeine Concentrations During the Early Growth of Coffea Arabica Plants

Increasing atmospheric [CO2] is thought to contribute to changes in precipitation patterns, increasing heatwaves and severe drought scenarios. However, how the combination of elevated [CO2] and progressive drought affect plant metabolism is poorly understood. Aiming to investigate the effects of this environmental condition on photosynthesis and specialized metabolites in leaves ofCoffea arabicaduring the early growth, plants fertilized with ambient (a[CO2]-400 ppm) and elevated (e[CO2]-800 ppm) [CO2] were exposed to well-watered (WW) or water-deficit (WD) regimes for 40 days. Over the 40-day-water-withdrawal, soil moisture, and leaf water potential decreased compared to WW-condition. Elevated [CO2] stimulates CO2assimilation (A) and intrinsic water use efficiency (iWUE) even under WD. Drought condition slightly changed stomatal conductance, transpiration rate and maximum quantum efficiency of photosystem II (PSII) regardless of [CO2] compared to WW-plants. Total soluble amino acid concentration did not change significantly, while total phenolic compounds concentration decreased under e[CO2] regardless of water regimes. The combination of e[CO2]+WD increased the 5-O-caffeoylquinic acid (5-CQA) and caffeine amounts by 40-day when compared to a[CO2]+WD plants. Altogether, these results suggest that e[CO2] buffers mild-drought stress in youngC. arabicaby increasing A, iWUE and stimulating changes in the leaf contents of 5-CQA and caffeine.

Improving quantity and quality of Thymus daenensis Celak. essential oil with application of Myco-Root biofertilizer under different irrigation levels

To determine the effects of Myco-Root biofertilizer and different irrigation levels on the content and essential oil compounds of thyme (Thymus daenensis Celak.), a factorial experiment was conducted in a completely randomized design with eight treatments and three replications in the greenhouse of Plant Production and Genetics department, Faculty of Agriculture, University of Maragheh, Iran, in 2020. The factors included drought stress at four levels of without stress (irrigation at field capacity (FC) as a control), mild (irrigation at 75% FC), moderate (irrigation at 55% FC), and severe (irrigation at 35% FC) stresses and biofertilizer at two levels of inoculation and non-inoculation with Myco-Root. The results demonstrated that the fresh and dry weight of leaves, stem dry weight, total dry weight, leaf relative water content, chlorophylls a and b and total chlorophyll content, and root colonization percentage decreased significantly with increasing the water deficit level. However, the carotenoid content and essential oil percentage showed an increasing trend with increasing drought stress. The highest carotenoid content and essential oil percentage was obtained by using Myco-Root under moderate drought stress. Thymol, carvacrol, p -cymene, 1,8-cineole, (E)-caryophyllene, borneol, γ-terpinene, and α-pinene were identified as the major constituents of essential oil in the all treatments. The highest content of thymol was obtained under mild drought stress with the Myco-Root application. Furthermore, the highest content of carvacrol was recorded under mild, moderate, and severe drought stresses, respectively with the Myco-Root application. On average, the application of Myco-Root biofertilizer increased the content of thymol, carvacrol, 1,8-cineole, E-caryophyllene, borneol, and α-pinene by 4.19, 48.28, 15.93, 16.33, 14.15, and 3.78%, respectively compared to not using this biofertilizer. Overall, the results showed that some morphological and physiological traits of thyme decreased significantly with increasing the water deficit levels, but the application of Myco-Root biofertilizer could amend drought stress and improve the growth, percentage and essential oil quality of the plant. Thus, the use of Myco-Root biofertilizer instead of chemical fertilizers could be recommended to achieve the sustainable agriculture in the thyme cultivation.

Leaf Age-Dependent Photosystem II Photochemistry and Oxidative Stress Responses to Drought Stress in Arabidopsis thaliana Are Modulated by Flavonoid Accumulation.

We investigated flavonoid accumulation and lipid peroxidation in young leaves (YL) and mature leaves (ML) of Arabidopsis thaliana plants, whose watering stopped 24 h before sampling, characterized as onset of drought stress (OnDS), six days before sampling, characterized as mild drought stress (MiDS), and ten days before sampling, characterized as moderate drought stress (MoDS). The response to drought stress (DS) of photosystem II (PSII) photochemistry, in both leaf types, was evaluated by estimating the allocation of absorbed light to photochemistry (ΦPSII), to heat dissipation by regulated non-photochemical energy loss (ΦNPQ) and to non-regulated energy dissipated in PSII (ΦNO). Young leaves were better protected at MoDS than ML leaves, by having higher concentration of flavonoids that promote acclimation of YL PSII photochemistry to MoDS, showing lower lipid peroxidation and excitation pressure (1 − qp). Young leaves at MoDS possessed lower 1 − qp values and lower excess excitation energy (EXC), not only compared to MoDS ML, but even to MiDS YL. They also possessed a higher capacity to maintain low ΦNO, suggesting a lower singlet oxygen (1O2) generation. Our results highlight that leaves of different developmental stage may display different responses to DS, due to differential accumulation of metabolites, and imply that PSII photochemistry in Arabidopsis thaliana may not show a dose dependent DS response.

Drought resistance mechanisms of Phedimus aizoon L.

Phedimus aizoon L. is a drought-resistant Chinese herbal medicine and vegetable. However, its drought tolerant limit and the mechanism of drought tolerance are unknown, which restricts the promotion of water-saving cultivation of Phedimus aizoon L. in arid areas. To solve the above problem, we carried out a 30-day-long drought stress experiment in pots that presented different soil water contents and were divided into four groups: control check, 75–80% of the maximum water-holding capacity (MWHC); mild drought, 55–60%; moderate drought, 40–45%; and severe drought, 20–25%. The dynamic changes in both plant physiological indexes from 10 to 30 days and leaf anatomical structure on the 30th day of stress were recorded. The results show that Phedimus aizoon L. grew normally under mild drought stress for 30 days, but the growth of the plants became inhibited after 20 days of severe drought and after 30 days of moderate drought. At the same time, Phedimus aizoon L. physiologically responded to cope with drought stress: the growth of the root system accelerated, the waxy layer of the leaves thickened, and the dark reactions of the plants transformed from those of the C3 cycle to CAM. The activity of antioxidant enzymes (SOD, POD and CAT) continuously increased to alleviate the damage caused by drought stress. To ensure the relative stability of the osmotic potential, the contents of osmoregulatory substances such as proline, soluble sugars, soluble protein and trehalose increased correspondingly. Although Phedimus aizoon L. has strong drought stress resistance, our experimental results show that the soil available water content should not be less than 27% during cultivation.

Is there any relationship between agronomic traits, soil properties and essential oil profile of peppermint (Mentha piperita L.) treated by fertiliser treatments and irrigation regimes?

AbstractOne of the greatest challenges in recent years is providing enough food to feed the increasing world population, with limited freshwater resources. However, effective fertiliser management also has a fundamental role to improve yield quality and quantity. Organic fertiliser not only supplements nutrients but also improves physicochemical and biological soil properties. A 2‐year field experiment was conducted to examine the influence of urea and vermicompost fertiliser on oil phytochemical properties of peppermint pH, soil cation exchange capacity (CEC) and organic carbon of experimental site under three irrigation regimes in 2018 and 2019. The experiments had three water deficit regimes (no stress, moderate, and severe drought stress) as a main plot. The subplot division consisted of six fertiliser treatments: unfertilised (control); 140 kg urea ha−1; 105 kg urea ha−1 + 3.3 ton vermicompost ha−1; 70 kg urea ha−1 + 6.6 ton vermicompost ha−1; 35 kg urea ha−1 + 10 ton vermicompost ha−1; and 13.5 ton vermicompost ha−1. The maximum leaf area index (4.29) and dry matter weight (3,803 kg ha−1) were observed in control irrigation, while the highest essential oil content (0.97%) could be seen under mild water deficit stress. Additionally, the highest organic carbon and CEC were obtained under well‐watered conditions at 1.20% and 6.41 (meq 100 g soil−1), respectively. Dry matter weight and essential oil content increased considerably in response to increasing vermicompost in fertiliser treatments, and the highest content of these traits were observed in 2019 and with 13.5 ton vermicompost ha−1. The menthol content increases in response to deficit irrigation and integrated fertiliser. These data indicate that mild drought stress can increase the synthesis of medical compounds and vermicomposting can alleviate the impact of drought by conserving soil moisture as an acclimation mechanism to improve nutrient uptake and avoid yield losses.

Crop yield and irrigation water productivity of silage maize under two water stress strategies in semi-arid environment: Two different pot and field experiments

Research on water stress strategies (WSS) and crop response to water stress is important to improve irrigation water productivity (WPI) and crop production especially for regions where water is a limited resource. This study was conducted to assess (i) the response of silage maize to water stress at different growth stages for contrasting water stress strategies in the semi-arid environment under pot and field experiments irrigated by a drip-tape system, (ii) to determine the relationship between applied water and total biomass (TB) in different WSS in both experiments. The hybrid 704-single-cross of maize was assessed at pot experiment during 2009 and 2010 and field experiment was conducted in 2017 under two WSS including WS1 (same irrigation event with different applied water depth) and WS2 (same applied water depth in different irrigation event) at three growth stages. Each WSS consisted of four different irrigation levels, including severe, moderate, and mild drought stress and a full irrigation. In both pot and field experiments, severe drought stress under WS1 and WS2 strategies led to a depression in LA and TB at tassel (S2) and silage harvest (S3) stages. At each growth stage, WPI values decreased with increasing water-deficit levels in both WSS’s and experiments. We found a linear relationship between TB and applied water for WS1 and WS2 in both experiments. However, the yield performance per unit of water used was higher for WS1 than for WS2. The yield response factor to stress (Ky) values for LA and TB were higher under WS2 than WS1 in both experiments, indicating that WS1 can be employed as an effective deficit irrigation management under the drip-tape irrigation system for maize in an arid area with shortage of water.

EMS Derived Wheat Mutant BIG8-1 (Triticum aestivum L.)-A New Drought Tolerant Mutant Wheat Line.

Drought response in wheat is considered a highly complex process, since it is a multigenic trait; nevertheless, breeding programs are continuously searching for new wheat varieties with characteristics for drought tolerance. In a previous study, we demonstrated the effectiveness of a mutant known as RYNO3936 that could survive 14 days without water. In this study, we reveal another mutant known as BIG8-1 that can endure severe water deficit stress (21 days without water) with superior drought response characteristics. Phenotypically, the mutant plants had broader leaves, including a densely packed fibrous root architecture that was not visible in the WT parent plants. During mild (day 7) drought stress, the mutant could maintain its relative water content, chlorophyll content, maximum quantum yield of PSII (Fv/Fm) and stomatal conductance, with no phenotypic symptoms such as wilting or senescence despite a decrease in soil moisture content. It was only during moderate (day 14) and severe (day 21) water deficit stress that a decline in those variables was evident. Furthermore, the mutant plants also displayed a unique preservation of metabolic activity, which was confirmed by assessing the accumulation of free amino acids and increase of antioxidative enzymes (peroxidases and glutathione S-transferase). Proteome reshuffling was also observed, allowing slow degradation of essential proteins such as RuBisCO during water deficit stress. The LC-MS/MS data revealed a high abundance of proteins involved in energy and photosynthesis under well-watered conditions, particularly Serpin-Z2A and Z2B, SGT1 and Calnexin-like protein. However, after 21 days of water stress, the mutants expressed ABC transporter permeases and xylanase inhibitor protein, which are involved in the transport of amino acids and protecting cells, respectively. This study characterizes a new mutant BIG8-1 with drought-tolerant characteristics suited for breeding programs.