Mild Drought Research Articles

Transcriptomic and Metabolomic Analyses Reveal Key Metabolites, Pathways and Candidate Genes in Sophora davidii (Franch.) Skeels Seedlings Under Drought Stress.

Soil aridification and desertification are particularly prominent in China’s karst areas, severely limiting crop yields and vegetation restoration. Therefore, it is very important to identify naturally drought-tolerant plant species. Sophora davidii (Franch.) Skeels is resistant to drought and soil infertility, is deeply rooted and is an excellent plant material for soil and water conservation. We studied the transcriptomic and metabolomic changes in S. davidii in response to drought stress (CK, control; LD, mild drought stress; MD, moderate drought stress; and SD, severe drought stress). Sophora davidii grew normally under LD and MD stress but was inhibited under SD stress; the malondialdehyde (MDA), hydrogen peroxide (H2O2), soluble sugar, proline, chlorophyll a, chlorophyll b and carotenoid contents and ascorbate peroxidase (APX) activity significantly increased, while the superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities and soluble protein content significantly decreased. In the LD/CK, MD/CK and SD/CK comparison groups, there were 318, 734 and 1779 DEGs, respectively, and 100, 168 and 281 differentially accumulated metabolites, respectively. Combined analysis of the transcriptomic and metabolomic data revealed the metabolic regulation of S. davidii in response to drought stress. First, key candidate genes such as PRR7, PRR5, GI, ELF3, PsbQ, PsaK, INV, AMY, E2.4.1.13, E3.2.1.2, NCED, PP2C, PYL, ABF, WRKY33, P5CS, PRODH, AOC3, HPD, GPX, GST, CAT and SOD1 may govern the drought resistance of S. davidii. Second, three metabolites (oxidised glutathione, abscisic acid and phenylalanine) were found to be related to drought tolerance. Third, several key candidate genes and metabolites involved in 10 metabolic pathways were identified, indicating that these metabolic pathways play an important role in the response to drought in S. davidii and possibly other plant species.

Plant growth-promoting rhizobacteria Shewanella putrefaciens and Cronobacter dublinensis enhance drought tolerance of pearl millet by modulating hormones and stress-responsive genes.

Drought is a major abiotic stress that affects crop productivity. Endophytic bacteria have been found to alleviate the adverse effects of drought on plants. In the present study, we evaluated the effects of two endophytic bacteria Shewanella putrefaciens strain MCL-1 and Cronobacter dublinensis strain MKS-1 on pearl millet (Pennisetum glaucum (L.) R. Br.) under drought stress conditions. Pearl millet plants were grown under three water levels: field capacity (FC), mild drought stress (MD), and severe drought stress (SD). The effects of inoculation on plant growth, physiological attributes, phytohormone content, and drought stress-responsive genes were assessed. The inoculation of pearl millet seeds with endophytes significantly improved shoot and root dry weight and root architecture of plants grown under FC and drought stress conditions. There was a significant increase in relative water content and proline accumulation in the inoculated plants. Among the phytohormones analyzed, the content of ABA and IAA was significantly higher in endophyte-treated plants under all moisture regimes than in uninoculated plants. C. dublinensis-inoculated plants had higher GA content than uninoculated plants under all moisture regimes. The expression level of genes involved in phytohormone biosynthesis (SbNCED, SbGA20oX, and SbYUC) and coding drought-responsive transcription factors (SbAP2, SbSNAC1 and PgDREB2A) was significantly higher under SD in endophyte-inoculated plants than in uninoculated plants. Thus, these endophytic bacteria presumably enhanced the tolerance of pearl millet to drought stress by modulating root growth, plant hormones, physiology and the expression of genes involved in drought tolerance.

Overexpression of Arabidopsis nucleolar GTP-binding 1 (NOG1) proteins confers drought tolerance in rice.

As a major adverse environmental factor in most parts of the world, drought causes substantial crop yield losses. Rice (Oryza sativa) is one of the staple foods for more than one-half of the world's population. Rice plants are sensitive to even mild drought stress and need almost twice the amount of water compared to wheat (Triticum aestivum) or maize (Zea mays). Arabidopsis (Arabidopsis thaliana) small GTPase Nucleolar GTP-binding protein 1 (AtNOG1) plays a role in biotic stress tolerance. Here, we created transgenic rice lines constitutively overexpressing AtNOG1-1 or AtNOG1-2. We also developed rice RNA interference (RNAi) lines that show downregulation of OsNOG1. AtNOG1-1 and AtNOG1-2 overexpressors showed enhanced drought tolerance without compromising grain yield, whereas OsNOG1-RNAi was more susceptible to drought when compared to wild-type plants. Analysis of physiological parameters showed increased cell sap osmolality, relative water content, and abscisic acid (ABA) level, but decreased leaf water loss in AtNOG1-1 or AtNOG1-2 overexpressor lines compared to the control. We found upregulation of several genes involved in ABA and jasmonic acid (JA) signaling, stomata regulation, osmotic potential maintenance, stress protection, and disease resistance in AtNOG1-1 and AtNOG1-2 overexpressor lines compared to the control. We elucidated the role of NOG1-2 and NOG1-1 in regulation of silica body formation around stomata to prevent transpirational water loss. These results provide an avenue to confer drought tolerance in rice.

Assessment of drought, its causes and consequences in connection with local wisdom: a case study of Kohat basin drought-2017, Khyber Pakhtunkhwa, Pakistan

Extreme weather events are significantly increasing around the globe. Among these, drought is a unique environmental hazard. Its uniqueness is the length of time between the first indications and impacts upon the community. Droughts may occur for months, years and in some cases decades, affecting large geographical areas. This study aims to assess the occurrence, causes and impacts of drought regimes technically by using the Standardized Precipitation Index (SPI) technique and culturally by assessing the local people's indigenous knowledge. For this purpose, both primary and secondary data were collected. Historically recorded rainfall data were used to calculate SPI values to identify rainfall deficits for 3, 6 and 12 months timescales. Data about the indigenous knowledge was collected through focus group discussions and interviews with the community. Secondary data were collected from Agriculture Department, Irrigation department, BARANI research station and Pakistan Meteorological Department (PMD). The study results revealed that mild and moderate droughts are decreasing as the timescale increases. Contrary, severe and extreme droughts increase with the increase in timescales from 3 months to a year. Results also highlighted three extreme drought events recorded in the study area based on SPI-3 and SPI-6 timescales from 1954 to 2017. The number of extreme droughts based on SPI-12 is five in the selected timeframe. Furthermore, there was a significant reduction in agriculture production particularly in crops and vegetables during drought-2017. The findings of the study recommend that there is a need to improve the irrigation system. Wastage of floodwater should be controlled and conserved in small dams. Coordination amongst the stakeholders, advanced early warning system, awareness and planning at the local are significant measures to be taken in the study area to combat the problem.

Non-target and suspect-screening analyses of hydroponic soybeans and passive samplers exposed to different watershed irrigation sources

Water scarcity increases the likelihood of irrigating food crops with municipal wastewater that may pose potential dietary risks of regulated and non-regulated organic chemical uptake to edible plant tissues. Only a few studies have used high resolution mass spectrometry (HRMS) to assess the uptake of chemicals of concern into food crops. This study used non-target and suspect-screening analyses to compare total chemical features, tentatively identified chemicals (TICs), and EPA ToxCast chemicals in soybean plants and passive samplers exposed to five different irrigation sources that were collected from an agricultural watershed during mild drought conditions. Secondary-treated municipal wastewater effluent, two surface waters, two ground waters, and deionized municipal tap water were used for two hydroponic experiments: soybean roots and shoots and Composite Integrative Passive Samplers (CIPS) harvested after fourteen days of exposure and soybeans after fifty-six days. CIPS were sealed in separate glass amber jars to evaluate their efficacy to mimic chemical features, TICs, and ToxCast chemical uptake in plant roots, shoots, and beans. Total soybean biomass and water use were greatest for tap water, municipal wastewater, and surface water downstream of the municipal wastewater facility relative to groundwater samples and surface water collected upstream of the wastewater facility. ToxCast chemicals were ubiquitous across watershed irrigation sources in abundance, chemical use category, and number. Wastewater-exposed soybeans had the fewest extractable TICs in plant tissues of all irrigation sources. More ToxCast chemicals were identified in CIPS than extracted from irrigation sources by solid phase extraction. ToxCast chemicals in beans and CIPS were similar in number, chemical use category, and log Kow range. CIPS appear to serve as a useful surrogate for ToxCast chemical uptake in beans, the edible food product.

Paclobutrazol alleviates seed germination and growth inhibition in Amorpha fruticosa under PEG-induced drought stress

ABSTRACT An in-depth quantitative analysis of the relationships between plant functional and physiological characteristics in arid areas will help to explore the response of xerophytic shrubs in the desert. Therefore, it is necessary to study the vegetation in arid areas. Through artificial intervention, exploring whether the medicament (Paclobutrazol, Pbz) can improve the adaptation of plants to the arid environment. In this study, the Amorpha fruticosa seeds soaked by Pbz at various concentrated applications at 150, 300, 450, and 600 mg/L (T1, T2, T3, T4) and then to explore the optimum concentration of drought-stress resistance. The results showed that seed germination was increased by 35.2% (p < 0.05) after 450 mg/L (T3) Pbz immersion compared with the control. Under mild drought stress, the seedling growth height and leaf area were reduced by 28.8% and 54.3%, then the stem diameter and seedling weight were increased by 1.6 and 2.4 times, respectively. Pbz significantly increased POD activity, SOD activity, Chlt content and Ss content (p < 0.05). However, it significantly inhibited the MDA content (p < 0.05). The combined effect showed that Pbz solution significantly improved seed germination quality, while effectively alleviating drought stress on seedlings and delaying plant growth, with the best treatment of T3.

تأثیر کتیرا روی برخی خصوصیات مورفوفیزیولوژیک و مرتبط با عملکرد دانه گیاه سیاهدانه (Nigella sativa L.) تحت شرایط خشکی

Introduction In fact, drought is stress that restricts the plant photosynthesis and causing changes in the chlorophyll content and damage to photosynthetic structures. One of the important reasons that environmental stresses such as drought reduce the growth and photosynthesis ability of the plant is a disturbance in the balance between production and removal of free oxygen radicals. Transpiration is a necessary process for photosynthesis and growth of plants but depending on the conditions may be harmful in some cases, so that the use of anti-transpirant can be one of the most effective methods for reducing the amount of water lost through transpiration and effective way to reduce the effects of drought stress on plants and adjustment the reduction of the yield due to water deficiency in arid and semi-arid regions. Climate change created in the world and the intensification of stresses caused by it, especially drought stress in arid and semi-arid regions such as Iran, make it difficult to achieve this goal. Therefore, finding strategies that can reduce the effects of water shortages on plant growth and yield and improve growth and yield can be very important. The aim of the present study was to investigate the effect of irrigation regimes and application of different concentrations of tragacanth (naturally dried exudate from some Astragalus species) on black cumin plant. Materials and Methods This research was carried out in a factorial experiment based on completely randomized design with three replications in a greenhouse of the Agriculture College of Kurdistan University in 2018. The experimental factors were including irrigation at three levels of 100% (full irrigation), 70% (mild drought stress), and 40% (severe drought stress) of field capacity of soil and spraying with tragacanth extract at six concentrations of 0, 1.25, 2.5, 5, 7.5, and 10 g/L. Spraying of this material was done using a back sprayer (Shark model) with a constant pressure of 2.4 bar and a volume of 250 liters of water per hectare. Before the data were analyzed, their normality test was performed using the Mini Tab software. After ensuring the normality of data, analysis of variance was performed using SAS ver. 9.3. LSD (Least significant difference) was used to compare the mean of treatments. The graphs are drawn using Excel software. Results and Discussion The results showed that increased drought stress intensity (irrigation reduction) led to the reduced leaf relative water content, Total chlorophyll content, efficiency of photosystem II, plant hight, number of capsules per plant, mean number of seeds per plant, biological yield and grain yield. The positive effects of tragacanth consumption on reducing and modifying the effects of drought stress on different levels of irrigation and different concentrations of tragacanth were different. In the present study, under full irrigation conditions, lower concentrations of tragacanth were useful, while in drought stress conditions, higher concentrations of tragacanth (except 10 g/L) were useful. In full irrigation, the concentration of 1.25 g/L was positive for all studied traits. In mild drought stress, the use of higher concentrations of tragacanth up to 5 g/L had the best effect and more concentrations resulted in a reverse effect on studied traits. In severe drought stress, the use of more concentrations of tragacanth extract was beneficial and improved the studied traits up to 7.5 g/L, but 10 g/L had a negative effect on these traits. Considering the effect of proper concentration of this material on the improvement of measured traits and increasing the grain yield compared to non-application of tragacanth under severe and moderate drought stress conditions by 11.6% and 28.2%, respectively. Conclusion The results of this study indicated the different effects of various concentrations of tragacanth material in different levels of irrigation on studied traits of black cumin. Therefore, it can be concluded that the application of different concentrations of tragacanth gum was completely dependent on the plant's water status. So that, using higher concentrations of tragacanth gum in drought stress conditions had a more positive effect on the plant, and vice versa, using a lower concentration of this material was useful in full irrigation. The effect of tragacanth gum on reducing and modifying the effects of drought stress in different plants requires further studies and extensive research. Tragacanth gum can be introduced as a new anti-transpirant agent with natural origin and its application can be useful and recommended in areas exposed to drought stress.

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.

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.

Effects of different concentrations of super-absorbent polymers on soil structure and hydro-physical properties following continuous wetting and drying cycles

Super-absorbent polymers (SAPs) are widely used chemical water-saving materials, which play an active role in the accumulation of soil water and the improvement of soil structure. Little is known about their performance with repeated usage or about factors influencing their efficiency under alternate wetting and drying cycles. In this study, various concentrations of SAP (0, 0.1, 0.2 and 0.3%) in soil following three continuous wetting and drying cycles (T1, T2 and T3), were studied to determine effects on soil structure stability and hydro-physical properties. The results indicated that the SAP improved soil water supply capacity under conditions of mild drought (T2) and sufficient irrigation (T3) at concentrations of 0.2 and 0.3%, but a reduction was observed under severe drought conditions (T1), which was negatively correlated with the SAP concentration. The physical adsorption of the SAP by soil and the chemical connection between the SAP and soil mineral colloids as Si-O-Si bonds, -OH bonds and different crystalline silica were the important factors that directly lead to the reduction of water retention capacities of the SAP with alternating wet and dry conditions. Compared with the control, the soil liquid phase ratios of the SAP treatments were increased by 8.8–202.7% in the T1 and T2 cycles, which would have led to a decrease in the soil air phase ratios. After repeated wetting and drying cycles, the SAP treatments increased the amount of >0.25 mm soil aggregates and the contents of water-stable macro-aggregate (R0.25), and decreased the amount of <0.053 mm soil aggregates, especially with higher concentrations of the SAP. Increases in mean weight diameter (MWD) and geometric mean diameter (GMD), and declines in fractal dimension (D) and unstable aggregates index (ELT) were all observed with the SAP treatments, which indicated an improvement in soil stability and structure. It was concluded that the distribution and stability of soil aggregates and soil water supply capacity was closely related to SAP concentration, soil moisture condition and the interaction between the SAP and soil particles.

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

Research the drought characteristics of Ninh Thuan province through the Rainfall Anomaly Index (RAI), Standardized Precipitation Index (SPI), and the Moisture Index (MI)

This article studies the drought characteristics of the Ninh Thuan province in the past through meteorological data for the period 1986-2016. The study used three main indicators to study drought, namely, the Rainfall Anomaly Index (RAI), Standardized Precipitation Index (SPI), and Moisture Index (MI). Besides, the study also used non-parametric analysis to study trends and Spearman's rho to study the correlation between the indexes. The results of the study showed the occurrence of drought in the period 1986-2016 with different developments and frequencies, in which the period 1986-97 drought appeared continuously. According to RAI's drought index, the drought occurs 15 times with a frequency of severe drought of 12.5% and mild drought of 34.4%. SPI's drought index shows the drought happened 26 times with a severe drought in 1988. Drought occurred 31 times during the study period, 77% of the time, and the severe drought only occurred in 1998, according to the drought index MI. Additionally, the study also identified the trend of changes in drought indicators in the future and showed a trend of reducing drought in Ninh Thuan. The trend results show an average annual increase in RAI and MI of 0.01 and SPI of 0.08. To consolidate and evaluate the significance, the study also evaluated the correlation between indicators, and the results met the requirements with a value of &gt; 0.84. The three indexes have Cronbach's Alpha reliability is 0.78, in which, the SPI index correlates most strongly with RAI and MI at 0.92 and 0.94, respectively. This result will help local authorities and policymakers have more methods to study future droughts and develop solutions to socio-economic development in Ninh Thuạn in the context of drought.

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

Hydrological Drought Analysis for Bolu City with Streamflow Drought Index

Hydrological drought refers to the decrease in the amount of water found in surface or groundwater resources and monitoring of this natural disaster is very important due to causing serious problems in drinking and irrigation water supply and hydroelectric energy production. In this study, hydrological drought analysis was made for two streams in Bolu city located in the Western Black Sea Region in the north of Turkey and 3, 6 and 12 month streamflow drought indices were calculated by using the Streamflow Drought Index method. For this aim, the streamflow data of Bolu stream - Beşdeğirmen and Ulusu - Afatlar streamflow monitoring stations were used. According to the results, extreme and severedroughts were determined for two stream flow stations and it is seen that drought periods varied between 1 and 9 years. The most severe and longest droughts were detected for Bolu stream - Beşdeğirmen station. Mild droughts are much higher than moderate, severe and extreme droughts. It has been observed that the severity and number of drought for Bolu stream - Beşdeğirmen station have increased in recent years. In order to reduce the effects of hydrological drought, hydrological drought should be monitored continuously and necessary precautions should be taken regarding the management of water resources. People should be informed about water consumption and so waste should be prevented. Interms of irrigation water, drip irrigation method should be used instead of flood irrigation or sprinkler irrigation methods. For this aim, farmers should be made aware of this issue. Alternative renewable energy sources or other energy sources should be used for reductions in hydroelectric energy production.

WUSCHEL-related homeobox family genes in rice control lateral root primordium size

The development of a plastic root system is essential for stable crop production under variable environments. Rice plants have two types of lateral roots (LRs): S-type (short and thin) and L-type (long, thick, and capable of further branching). LR types are determined at the primordium stage, with a larger primordium size in L-types than S-types. Despite the importance of LR types for rice adaptability to variable water conditions, molecular mechanisms underlying the primordium size control of LRs are unknown. Here, we show that two WUSCHEL-related homeobox (WOX) genes have opposing roles in controlling LR primordium (LRP) size in rice. Root tip excision on seminal roots induced L-type LR formation with wider primordia formed from an early developmental stage. QHB/OsWOX5 was isolated as a causative gene of a mutant that is defective in S-type LR formation but produces more L-type LRs than wild-type (WT) plants following root tip excision. A transcriptome analysis revealed that OsWOX10 is highly up-regulated in L-type LRPs. OsWOX10 overexpression in LRPs increased the LR diameter in an expression-dependent manner. Conversely, the mutation in OsWOX10 decreased the L-type LR diameter under mild drought conditions. The qhb mutants had higher OsWOX10 expression than WT after root tip excision. A yeast one-hybrid assay revealed that the transcriptional repressive activity of QHB was lost in qhb mutants. An electrophoresis mobility shift assay revealed that OsWOX10 is a potential target of QHB. These data suggest that QHB represses LR diameter increase, repressing OsWOX10 Our findings could help improve root system plasticity under variable environments.

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.

Identification of Regional Drought Processes in North China Using MCI Analysis

Comprehensive identification of drought events is of great significance for monitoring and evaluating drought processes. Based on the date of daily precipitation, temperature and drought-affected area of 403 meteorological stations in North China from 1960 to 2019, the Comprehensive Drought Process Intensity Index (CDPII) has been developed by using the Meteorological-drought Composite Index (MCI) and regional drought process identification method, as well as the EIDR theory method. The regional drought processes in the past 60 years in North China, including Beijing, Tianjin, Hebei, Shanxi and Middle Inner Mongolia, were analyzed and identified. The result shows that the distribution characteristic of droughts with different intensities is as follows: The number of days of all annual-average mild droughts, moderate droughts and severe droughts was highest in Tianjin and that of extreme droughts was highest in Shanxi. The number of days of mild droughts was highest in May and lowest in January. The number of days of moderate droughts was highest in June. The number of days with mild and moderate drought showed an overall increasing trend, while the number of days with severe drought and above showed an overall decreasing trend (through a 95% significance test). The number of drought days was the highest in the 1990s. The annual frequency of drought is between 66.7% and 86.7%; the drought frequency in Hebei is the highest at 86.7%, followed by Beijing at 80%. There were 75 regional drought processes in North China from 1960 to 2019, and the correlation coefficient between process intensity and the drought-affected area was 0.55, which passed the 99% significance test. The comprehensive intensity of drought process from 27 April to 1 September 1972 was the strongest. From 18 May to 31 October 1965, the drought lasted 167 days. The overall drought intensity had a slight weakening trend in the past 60 years. A total of 75 regional drought processes occurred in North China, and the process intensity showed a trend of wavy decline with a determination coefficient (R2) of 0.079 (95% significance test). Overall, the regional drought process identification method and strength assessment result tally with the drought disaster, which can better identify the regional drought process. Furthermore, including the last days, the average intensity, average scope comprehensive strength, there are many angles to monitor and evaluate the drought and drought process. These provide a reference for drought control and decision-making.

Differential Variation in Non-structural Carbohydrates in Root Branch Orders of Fraxinus mandshurica Rupr. Seedlings Across Different Drought Intensities and Soil Substrates.

Non-structural carbohydrates (NSCs) facilitate plant adaptation to drought stress, characterize tree growth and survival ability, and buffer against external disturbances. Previous studies have focused on the distribution and dynamics of NSCs among different plant organs under drought conditions. However, discussion about the NSC levels of fine roots in different root branch orders is limited, especially the relationship between fine root trait variation and NSC content. The objective of the study was to shed light on the synergistic variation in fine root traits and NSC content in different root branch orders under different drought and soil substrate conditions. The 2-year-old Fraxinus mandshurica Rupr. potted seedlings were planted in three different soil substrates (humus, loam, and sandy–loam soil) and subjected to four drought intensities (CK, mild drought, moderate drought, and severe drought) for 2 months. With increasing drought intensity, the biomass of fine roots decreased significantly. Under the same drought intensity, seedlings in sandy–loam soil had higher root biomass, and the coefficient of variation of 5th-order roots (37.4, 44.5, and 53% in humus, loam, and sandy–loam soil, respectively) was higher than that of lower-order roots. All branch order roots of seedlings in humus soil had the largest specific root length (SRL) and specific root surface area (SRA), in addition to the lowest diameter. With increasing drought intensity, the SRL and average diameter (AD) of all root branch orders increased and decreased, respectively. The fine roots in humus soil had a higher soluble sugar (SS) content and lower starch (ST) content compared to the loam and sandy–loam soil. Additionally, the SS and ST contents of fine roots showed decreasing and increasing tendencies with increasing drought intensities, respectively. SS and ST explained the highest degree of the total variation in fine root traits, which were 32 and 32.1%, respectively. With increasing root order, the explanation of the variation in root traits by ST decreased (only 6.8% for 5th-order roots). The observed response in terms of morphological traits of different fine root branch orders of F. mandshurica seedlings to resource fluctuations ensures the maintenance of a low cost-benefit ratio in the root system development.

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.

Integrated transcriptome and small RNA sequencing analyses reveal a drought stress response network in Sophora tonkinensis

BackgroundSophora tonkinensis Gagnep is a traditional Chinese medical plant that is mainly cultivated in southern China. Drought stress is one of the major abiotic stresses that negatively impacts S. tonkinensis growth. However, the molecular mechanisms governing the responses to drought stress in S. tonkinensis at the transcriptional and posttranscriptional levels are not well understood.ResultsTo identify genes and miRNAs involved in drought stress responses in S. tonkinensis, both mRNA and small RNA sequencing was performed in root samples under control, mild drought, and severe drought conditions. mRNA sequencing revealed 66,476 unigenes, and the differentially expressed unigenes (DEGs) were associated with several key pathways, including phenylpropanoid biosynthesis, sugar metabolism, and quinolizidine alkaloid biosynthesis pathways. A total of 10 and 30 transcription factors (TFs) were identified among the DEGs under mild and severe drought stress, respectively. Moreover, small RNA sequencing revealed a total of 368 miRNAs, including 255 known miRNAs and 113 novel miRNAs. The differentially expressed miRNAs and their target genes were involved in the regulation of plant hormone signal transduction, the spliceosome, and ribosomes. Analysis of the regulatory network involved in the response to drought stress revealed 37 differentially expressed miRNA-mRNA pairs.ConclusionThis is the first study to simultaneously profile the expression patterns of mRNAs and miRNAs on a genome-wide scale to elucidate the molecular mechanisms of the drought stress responses of S. tonkinensis. Our results suggest that S. tonkinensis implements diverse mechanisms to modulate its responses to drought stress.