Differential regulation of flower transpiration during abiotic stress in plants

Heat waves, occurring during droughts, can have a devastating impact on yield, especially if they happen during the flowering and seed set stages of the crop cycle. Global warming and climate change are driving an alarming increase in the frequency and intensity of combined drought and heat stress episodes, critically threatening global food security. Previous studies revealed that during a combination of drought and heat stress stomata on leaves of many plants are closed, preventing cooling by transpiration. Because high temperature is detrimental to reproductive processes, essential for plant yield, we measured the inner temperature, transpiration, and sepal stomatal aperture of closed soybean flowers, developing on plants subjected to a combination of drought and heat stress. Here, we report that during a combination of drought and heat stress soybean plants prioritize transpiration through flowers over transpiration through leaves by opening their flower stomata, while keeping their leaf stomata closed. This acclimation strategy, termed differential transpiration, lowers flower inner temperature by about 2-3oC, protecting reproductive processes at the expense of vegetative tissues. Manipulating stomatal regulation, stomatal size and/or stomatal density of flowers could therefore serve as a viable strategy to enhance the yield of different crops and mitigate some of the current and future impacts of global warming and climate change on agriculture.

Genetic Analysis of Early White Quality Protein Maize Inbreds and Derived Hybrids under Low-Nitrogen and Combined Drought and Heat Stress Environments

An increase in the average global temperature and drought is anticipated in sub-Saharan Africa (SSA) as a result of climate change. Therefore, early white quality protein maize (QPM) hybrids with tolerance to combined drought and heat stress (CDHS) as well as low soil nitrogen (low-nitrogen) have the potential to mitigate the adverse effects of climate change. Ninety-six early QPM hybrids and four checks were evaluated in Nigeria for two years under CDHS, low-nitrogen, and in optimal environments. The objectives of this study were to determine the gene action conditioning grain yield, assess the performance of the early QPM inbred lines and identify high yielding and stable QPM hybrids under CDHS, low-nitrogen and optimal environment conditions. There was preponderance of the non-additive gene action over the additive in the inheritance of grain yield under CDHS environment conditions, while additive gene action was more important for grain yield in a low-nitrogen environment. TZEQI 6 was confirmed as an inbred tester under low N while TZEQI 113 × TZEQI 6 was identified as a single-cross tester under low-nitrogen environments. Plant and ear aspects were the primary contributors to grain yield under CDHS and low-nitrogen environments. TZEQI 6 × TZEQI 228 and the check TZEQI 39 × TZEQI 44 were the highest yielding under each stress environment and across environments. Hybrid TZEQI 210 × TZEQI 188 was the most stable across environments and should be tested on-farm and commercialized in SSA.

Harnessing Beneficial Plant-Microbe Interactions for Enhanced Plant Adaptation to Abiotic Stresses

Boosting crop production is a vital venture for enhancement of humanity. However, it remains a dream, especially in developing countries. To attain food security at household level, productivity is constrained by a several biotic and abiotic stresses. Yield losses are usually influenced by abiotic stresses, particularly drought and heat stress, and poor soil fertility. Optimal crop production under these stress factors requires substantial inputs, including irrigation and heavy fertilization, strategies which majority of farmers in poor countries lack capacity to exploit. Therefore, much more sustainable and accessible alternatives need to be developed in order to address the problem of food insecurity. Recently, research has proven that plant adaptation to abiotic stresses can be promoted by beneficial microbial species, especially those that reside in the rhizosphere. For instance, mycorrhizal fungi have been found to expand the root system of plants to access more water and nutrients. In-depth understanding of the mechanisms underlying beneficial plant-microbe interactions is key in development of holistic programs for boosting yields under abiotic stress conditions. This chapter seeks to unravel the mechanisms underlying beneficial plant-microbe interactions and the importance of these interactions in stress-adaptation.

Physiological Plasticity of Green Gram Stomata to Photosynthesis Traits under Interactive Effects of Elevated CO2, Drought and Heat Stress

Heat waves and droughts are projected to become more widespread as a result of climate change. At the same time, CO2 levels are predicted to have doubled by 2100. The stomatal regulation and gas exchange characteristics were assessed in 25 days old plants of green gram (var Co 8) by exposing them to six different treatments namely, T1: a [CO2] + a T+ irrigation (100%), T2: a [CO2] + a T+ irrigation (50%), T3: a [CO2] + e T (40ºC) + irrigation (100%), T4: e [CO2] – 800 ppm + a T+ irrigation (100%), T5: a [CO2] + combined stress [e T (40ºC) + irrigation (50%) T6: e [CO2] – 800 ppm + combined stress [e T (40ºC) + irrigation (50%)]. The experiment was carried out using Completely Randomized Design (CRD) with three replications. All gas exchange parameters viz., ((photosynthesis rate, stomatal conductance, and transpiration rate) were determined before imposing stress and two weeks after imposing stress. Stomatal characters was examined two weeks after imposing stress. Elevated CO2 stress caused a reduction in stomatal frequency accompanied by larger stomatal size. The study revealed the positive effect of higher CO2 concentration on gas exchange traits of the C3 crops viz., green gram.

Assessing Drought and Heat Stress-Induced Changes in the Cotton Leaf Metabolome and Their Relationship With Hyperspectral Reflectance

The study of phenotypes that reveal mechanisms of adaptation to drought and heat stress is crucial for the development of climate resilient crops in the face of climate uncertainty. The leaf metabolome effectively summarizes stress-driven perturbations of the plant physiological status and represents an intermediate phenotype that bridges the plant genome and phenome. The objective of this study was to analyze the effect of water deficit and heat stress on the leaf metabolome of 22 genetically diverse accessions of upland cotton grown in the Arizona low desert over two consecutive years. Results revealed that membrane lipid remodeling was the main leaf mechanism of adaptation to drought. The magnitude of metabolic adaptations to drought, which had an impact on fiber traits, was found to be quantitatively and qualitatively associated with different stress severity levels during the two years of the field trial. Leaf-level hyperspectral reflectance data were also used to predict the leaf metabolite profiles of the cotton accessions. Multivariate statistical models using hyperspectral data accurately estimated (R2 > 0.7 in ∼34% of the metabolites) and predicted (Q2 > 0.5 in 15–25% of the metabolites) many leaf metabolites. Predicted values of metabolites could efficiently discriminate stressed and non-stressed samples and reveal which regions of the reflectance spectrum were the most informative for predictions. Combined together, these findings suggest that hyperspectral sensors can be used for the rapid, non-destructive estimation of leaf metabolites, which can summarize the plant physiological status.