Effects of phosphorus and iron on biomass production and nutrients partitioning in soybean cultivars under water stress condition

A pot experiment was conducted to investigate the effects of P and Fe application on the biomass production and nutrients partitioning of two soybeans (Glycine max. L. Merr) cultivars grown in carbonated chernoziom (low in Fe and P) under water stress conditions. P and Fe were applied at two levels (0 and 100 mg P kg-1 soil; 0 and 5 mg Fe kg-1 soil). Control plants were grown at 70% water holding capacity (WHC) while their counterparts were subjected to 35% WHC water stress at initial flowering stage for two weeks. Considerable variability was observed in leaves, roots dry mass accumulation and nodulation among the soybean cultivars (Zodiac, Licurici) at both P and Fe levels in relation to water regimes. The results showed that drought significantly reduced biomass production irrespective of nutrient supply and its adverse effect was more pronounced at low nutrient supply. Leaf development and nodules growth were the most sensitive to water deficit and insufficient nutrient supply. Adequate P and Fe supply increased dry matter production and nutrient concentrations for soybean cultivars. Phosphorus concentration in plant parts was significantly higher at nil Fe compared with Fe application. Phosphorus application decreased Fe allocation to the leaves. The experimental results demonstrated that there was a positive effect of P and Fe adequate nutrition on P use efficiency. Hence, the sufficient phosphorus and iron supply maintained growth at high level, improved P and Fe status and partially alleviated drought effect on soybean plants.

Salt and Drought Effect on Germination and Initial Growth of Lavandula stoechas: A Potential Candidate for Rehabilitation of the Mediterranean Disturbed Coastal Lands

Information relating to germination and seedling emergence of a plant aids in determining the species spatiotemporal distribution and also facilitates in designing appropriate plant management strategies within an ecosystem. Lavandula stoechas L. (Lamiaceae), a naturally occurring shrub, is particularly used in pharmaceutical and cosmetic industries. This species, indeed, has the potential for rehabilitation of degraded costal lands. However, various aspects of its seed biology have not yet been recognised. Here, we aimed to assess the effects of different soluble salts (NaCl, CaCl2, MgCl2 and Na2SO4) and drought (as simulated by polyethylene glycol, [PEG]6000) on seed germination patterns and early seedling growth responses. Seeds treated with five iso-concentration (0–100 mM) salinities and five PEG6000 (0 to −1 MPa) levels were incubated in a controlled germinator set at 20°C. The preliminary results revealed that seeds of L. stoechas lacked primary/innate dormancy and they germinated abundantly (89.2% germination) and fast (7.4% day−1) in the absence of stress. Regardless of the kind of salt applied, the germination percentage (GP) and germination rate index (GRI) fell significantly with increasing salinity, and germination ceased completely at 100 mM Na2SO4. In fact, the salinity tolerance index (STI) showed that, among all salts tested, Na2SO4 appeared to have more inhibitory action on germination. In addition, L. stoechas was found to be tolerant to moderate salty stress (<50 mM) in early growth phase. The salt solution parameters (i.e. concentration, electrical conductivity [EC] and salt content) were best correlated with seed/seedling metrics. pH was not a good predictor for salt effects at the germination/seedling stages. Overall, this species seems to be sensitive to drought at the germination and initial growth phases. The germination recovery potential of L. stoechas in both stresses stipulates that this species can be regarded as a promising candidate in the rehabilitation of Mediterranean disturbed coastal habitats.

Mecanismos de inducción de rizobios para reducir el estrés por sequía en las leguminosas

Drought is one of the main limitations of agricultural productivity and food security, in Andean mountain. The use of atmospheric nitrogen-fixing rhizobia in symbiosis with legumes, and tolerant to a wide range of adverse conditions, such as drought, is a great potential in sustainable agriculture. The aim of this review is to compile studies about drought stress effect on the legume-rhizobia symbiosis and rhizobia mechanisms to induce drought tolerance in legumes. The search for information was conducted from August to December 2020, using key terms. The drought effect on the nodulation and atmospheric nitrogen fixation process is made known, as well as the rhizobia ability to synthesize exopolysaccharides, enzymes, phytohormones, siderophores, osmolytes and solubilize phosphates as induction mechanisms to mitigate drought stress in legumes. This review will serve to propose future research using rhizobia to mitigate the drought effect on the legumes cultivation in environments such as the Andean mountains.

The Drought Effect on Morphophysiological Parameters and Crop Performance Indicators of the Studied Local Wheat Genotypes

Drought stress is the most important factor and an increasingly serious problem limiting the growth of wheat (Triticum aestivum L. / Triticum durum) in the world. Wheat possesses physiological mechanisms that allow it to adapt to the stress of drought and can vary depending on the genotype. The studies were carried out on wheat genotypes at the Absheron Experimental Base Station of the Azerbaijan Scientific Research Institute of Crop Husbandry. The experiment was designed in a factorial design with two treatments (irrigated and non-irrigated) and three repetitions during the 2020–2021 harvest season. Analysis of variance revealed significant differences between treatments and between varieties. The treatment × cultivar interaction was also significant for all traits, with the exception of grain per plant yield. Significant interactions showed that varieties performed differently under stressful conditions, but consistently with respect to grain yield. The studied varieties Giymatly-2/17, Gunashly and Tale-38 showed a minimal decrease in physiological characteristics, as well as in yield characteristics under stress during flowering, however, a decrease from low to high was observed under stress conditions compared with no stress. Correlations between morphological, physiological, and morphophysiological traits such as plant height, number of grains per ear, seed index, grain yield per plant, yield index, relative water content, stomatal conductance, leaf area and ear fertility have generally been reliable indicators for screening for drought tolerant wheat varieties and potentially higher yields. In addition, it is observed that improvement in any of these traits will lead to an increase in grain yield under water stress conditions.

Geospatial Analysis of the Impact of Flood and Drought Hazards on Crop Land and Its Relationship with Human Migration at the District Level in Uttar Pradesh, India

The main objective was to explore the connection between flood and drought hazards and their impact on crop land and human migration. The Flood and Drought effect on Cropland Index (FDCI), hot spot analysis and the Global Regression Analysis method was applied for the identification of the relationship between human migration and flood and drought hazards. The spatial pattern and hot and cold spots of FDCI, spatial autocorrelation and Getis-OrdGi* statistic techniques were used respectively. The FDCI was taken as an explanatory variable and human migration was taken as a dependent variable in the environment of the geographically weighted regression (GWR) model which was applied to measure the impact of flood and drought hazards on human migration. FDCI suggests a z-score of 4.9, which shows that the impact of flood and drought frequency on crop land is highly clustered. In the case of the hot spots analysis, out of seventy districts in Uttar Pradesh twenty-one were classified as hot spot and eight were classified as cold spots with a confidence level of 90 to 99%. Hot spot indicate maximum and cold spots show minimum impact of flood and drought hazards on crop land. The impact of flood and drought hazards on human migration show that there are fourteen districts where migration out is far more than predicted while there are ten districts where migration out is far lower.

Physiological response and secondary metabolites of three lavender genotypes under water deficit

Lavandula genus is a considerable medicinal plant in pharmaceutical and cosmetics industries. Considering increasing threat of drought in the world, it is important to identify genotypes which can tolerate drought. It is also important to characterize quantity and quality of essential oils, and tolerance indicators of these genotypes against drought stress. Therefore, an experiment was conducted in Gorgan University of Agricultural Sciences and Natural Resources, Iran, during 2017 and 2018, to investigate these factors. It was a factorial experiment based on randomized complete block design with two treatments, three genotypes (Lavandula angustifolia cv. Hidcote, Lavandula angustifolia cv. Munstead, and Lavandula stricta), and four levels of drought stress (irrigation regimes) (I1: 100–90% (control), I2: 80–70%, I3: 60–50% and I4: 30–40% of field capacity) which was done with three repetitions. Drought increased amount of proline in leaves, antioxidant activity, activity of catalase, peroxidase, ascorbate peroxidase, and superoxide enzymes, malondialdehyde content, total flavonoids, total phenol, total sugar and essential oil percentage. The PCA analysis of different irrigation regimes showed that in the first component, the best traits are antioxidant enzymes CAT, SOD, APX, while in the second component, only the trait Catalase is the best trait. The results of PCA analysis in lavender genotypes showed that L. stricta exhibits the most affected physiological changes while trying to adjust to changes in the water status of the environment, under the imposed conditions and shows the highest resistance. But it reduced dry weight of aerial parts, relative water content of leaves, and efficacy of essential oil. Lavandula stricta genotype had the highest amount of essential oil, but the highest dry weight of the aerial parts and essential oil yield were related to L. angustifolia cv. Hidcote and L. angustifolia cv. Munstead genotypes. In all evaluated genotypes, with increasing drought stress, monoterpene compounds were decreased and sesquiterpene compounds were increased. Totally it was shown that drought effect on evaluated traits depends on genotype and nature of traits; this indicates that by choosing drought-tolerant genotypes in breeding programs, high quantity and quality of essential oil, as well as tolerance to drought stress can be achieved.

Climate change experiment suggests divergent responses of tree seedlings in eastern North America’s Acadian Forest Region over the 21st century

In this study, we conducted a controlled experiment to assess the growth and survival of balsam fir (Abies balsamea (L.) Mill.), red spruce (Picea rubens Sarg.), and red maple (Acer rubrum L.) seedlings in response to warming, drought, and elevated CO2, as projected under RCP 8.5 for North America’s Acadian Forest Region. In response to warming, only red spruce increased in height; however, this effect varied by CO2 and soil moisture treatments. Under the drought treatment, red spruce biomass was not affected, but mortality increased by two percent. With warming, increases in balsam fir height growth were only detected under certain soil moisture and CO2 conditions. Balsam fir biomass decreased by 24% under drought, while mortality increased by 5 percent. Warming did not improve red maple height growth, but it remained 7-50 times greater than that of the conifers and no mortality was observed. Overall, CO2 enrichment increased height growth of droughted seedlings relative to the ambient treatment, demonstrating an amelioration of the negative drought effect. Balsam fir was the least adapted to warming and drought, while red spruce displayed some positive responses. Although growth of red maple seedlings did not increase with warming, they exhibited greater absolute growth and survival, which suggests red maple may outperform both conifers under a warming climate.

Diversity of Adult Caddisfly (Trichoptera) in Two Intermittent Streams During Dry Season in Phayao Province, Thailand

The effect of anthropogenic activities on natural intermittent stream and diversity of adult caddisfly were studied at the University of Phayao, Thailand. The caddisfly adults were collected monthly from 2 intermittent streams (the Huai Thub Chang and Huai Luang streams) from February to May 2015 (cool-dry to hot-dry season) using a black-light trap. Huai Thub Chang stream received wastewater from the oxidation pond, while Huai Luang stream was affected by an agricultural field of the university. Both streams are located in a deciduous forest. The 14 species of 7 families were collected and identified. Cheumatopsyche lucida (Hydropsychidae) and Leptocerus dirghachuka (Leptoceridae) were found in both streams. C. lucida was the most abundant species. Micrasema turbo, Amphipsyche meridiana, C. globosa, Diplectrona lavinia, Macrostemum dohrni, Marilia sumatrana, and Wormaldia relicta were found only in Huai Thub Chang stream, whereas C. dhanikari, Lepidostoma doligung and Chimarra toga were found only in Huai Luang stream. A high number of C. lucida in both streams from February to April reflected a drought effect on the emergence of the caddisflies. Huai Thub Chang stream had a higher diversity of Trichoptera species than Huai Luang stream because of the variety of substrate types which were suited for the larval stage, especially hydropsychids.

Drought stress-induced irregularities in male organ development cause stage-specific morpho-physiological and transcriptome changes in tomato

Drought limits the growth and productivity of plants. Reproductive development is sensitive to drought but the underlying physiological and molecular mechanisms remain unclear in tomato. Here, we investigated drought effect on tomato floral development using morpho-physiological and transcriptome analyses. Drought induced bud and flower abortions, and reduced fruit set/yield, triggered by male sterility due to abnormal anther and pollen development. Under drought stress (DS), anthers at pollen mother cell to meiotic (PMC-MEI) stage survived while anthers at tetrad to uninucleate microspore (TED-VUM) stage aborted. PMC-MEI stage had lower ABA increase, reduced IAA and higher sugar contents under DS relative to well-watered. However, TED-VUM stage had higher ABA increase, higher IAA level and no accumulation of soluble sugars, indicating abnormal carbohydrate and hormone metabolisms. Moreover, RNA-Seq analysis identified altogether ˃15,000 differentially expressed genes that were assigned to multiple pathways, suggesting tomato anthers utilize complicated mechanisms to cope with drought. Major genes involved in tapetum/microspore development and ABA homeostasis were drought-induced while those involved in sugar utilization and IAA metabolism were repressed at PMC-MEI stage. Our results suggest crosstalks between phytohormones and carbohydrate metabolism at different anther stages under DS and provide novel insight into molecular mechanisms of drought tolerance in tomato.