Drought stress negatively affects cotton pollen fertility, which in turn leads to a decrease in seed number per boll and boll weight. Exogenous melatonin application significantly enhances pollen fertility under drought conditions, while the specific underlying mechanisms remain unclear. A pot experiment was conducted using a cultivar Yuzaomian 9110 under two moisture treatments (soil relative water content at 75 +/- 5 % and 45 +/- 5 %) with two melatonin concentration (0 and 200 mu M) to investigate the effects of exogenous melatonin on the structural traits and physiological metabolism of cotton anthers and its' relationships with pollen fertility. Results demonstrated the significant impact of drought on anthers development and metabolism, with damage to the anther tapetum and decreased starch and adenosine triphosphate (ATP) contents, subsequently resulting in reduced pollen germination rate, seed number per boll and boll weight. Melatonin application in water-deficit anthers up-regulated the expression of sucrose transporter protein (GhSWEET55) and phosphate sucrose synthetase, promoting sucrose import and synthesis, respectively. However, it also increased sucrose synthase and acid convertase, accelerating sucrose decomposition and reducing its content. Additionally, melatonin application promoted starch accumulation in water-deficit anthers by enhancing activities of adenosine diphosphate glucose pyrophosphorylase and soluble starch synthase, meaning that potential energy storage was increased, which facilitated the formation of pollen fertility. Although melatonin application reduced the expression of pyruvate kinase (GhPK) and glucose 6-phosphogluconate dehydrogenase (GhG6PD) genes in water-deficit anthers, it upregulated hexokinase (GhHXK) and citrate synthase (GhCIT) expression, enhancing ATP content, and ultimately pollen fertility, seed number and boll weight under drought. In summary, exogenous melatonin preserved cotton pollen fertility under drought stress by regulating carbohydrate and energy metabolism, especially enhancing starch and ATP accumulation in anthers.

Sorghum [Sorghum bicolor (L.) Moench] grain yield is vulnerable to drought stress. Therefore, developing appropriate technologies to mitigate drought is essential. We hypothesize that inhibition of photosynthesis and reproductive success by drought in sorghum can be improved by enhanced osmolyte accumulation and antioxidant defence system by foliar application of nanoselenium. In this study, the ecotoxicity potential and the physiological basis of drought alleviation by nanoselenium were evaluated. Nanoselenium did not cause toxicity to soil, aquatic and terrestrial organisms up to 20 mg L-1.-1 . During drought, foliar application of nanoselenium at 20 mg L-1 reduced the transpiration rate (16 %) compared to water spray. The superoxide radical content (50 %), hydrogen peroxide content (35 %), and membrane damage (26 %) were reduced, indicating antioxidant activity was exerted by nanoselenium. In contrast, the leaf turgor potential (80 %), relative water content (17 %), reducing sugars (57 %), non-reducing sugars (11 %), and proline (35%) contents were increased by nanoselenium than water spray, indicating a higher tissue water content was maintained, which has increased the photosynthetic rate (26 %). Higher reproductive success in nanoselenium-sprayed plants under drought was associated with reproductive tissue morphology and an increased number of pollen grains attached to the stigma. Foliar application of nanoselenium at 20 mg L-1 increased seed-set percentage (21 %) and seed yield (26 %) under drought than control. A similar response was observed by foliar spray with sodium selenate. Overall, foliar application of nanoselenium at 20 mg L-1 improved the drought tolerance of sorghum by reducing the transpiration rate and increasing the antioxidant defense system. (c) 2024 SAAB. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Ice-wedge polygon (IWP) peatlands in the Arctic and Subarctic are extremely vulnerable to climatic and environmental change. We present the results of a multidisciplinary paleoenvironmental study on IWPs in the northern Yukon, Canada. High-resolution laboratory analyses were carried out on a permafrost core and the overlying seasonally thawed (active) layer, from an IWP located in a drained lake basin on Herschel Island. In relation to 14 Accelerator Mass Spectrometry (AMS) radiocarbon dates spanning the last 5000 years, we report sedimentary data including grain size distribution and biogeochemical parameters (organic carbon, nitrogen, C/N ratio, delta C-13), stable water isotopes (delta O-18, delta D), as well as fossil pollen, plant macrofossil and diatom assemblages. Three sediment units (SUS) correspond to the main stages of deposition (1) in a thermokarst lake (SW : 4950 to 3950 cal yrs BP), (2) during transition from lacustrine to palustrine conditions after lake drainage (SU2: 3950 to 3120 cal yrs BP), and (3) in palustrine conditions of the IWP field that developed after drainage (SU3: 3120 cal yrs BP to 2012 CE). The lacustrine phase (pre 3950 cal yrs BP) is characterized by planktonic-benthic and pioneer diatom species indicating circumneutral waters, and very few plant macrofossils. The pollen record has captured a regional signal of relatively stable vegetation composition and climate for the lacustrine stage of the record until 3950 cal yrs BP. Palustrine conditions with benthic and acidophilic diatom species characterize the peaty shallow-water environments of the low-centered IWP. The transition from lacustrine to palustrine conditions was accompanied by acidification and rapid revegetation of the lake bottom within about 100 years. Since the palustrine phase we consider the pollen record as a local vegetation proxy dominated by the plant communities growing in the IWP. Ice-wedge cracking in water-saturated sediments started immediately after lake drainage at about 3950 cal yrs BP and led to the formation of an IWP mire. Permafrost aggradation through downward closed-system freezing of the lake talik is indicated by the stable water isotope record. The originally submerged IWP center underwent gradual drying during the past 2000 years. This study highlights the sensitivity of permafrost landscapes to climate and environmental change throughout the Holocene. (C) 2016 Elsevier Ltd. All rights reserved.