The distribution and species of Ca2+ and subcellular localization of Ca2+ and Ca2+-ATPase in grape leaves of plants treated with fluoroglycofen

The neglected ammonia leaching calcium in anaerobic granular sludge

Previous researches have primarily emphasized the deleterious impacts of NH4+ on anaerobic granular sludge due to its biotoxicity. Despite this, the role of NH4+ as a monovalent cation in leaching multivalent Ca2+, thereby hindering granule formation and undermining its stability, remains underappreciated. This study investigated the potential of NH4+ to leach Ca2+ from anaerobic granular sludges. The results indicated that a shock loading of NH4+ at a concentration of 900 mg/L caused a Ca2+ leaching of 57.1 mg/L at pH 7.0. In an acidified environment (pH 5.0), the shock loading resulted in a Ca2+ release of 127.3 mg/L, a magnitude 5.24 times greater than the control group. The leaching process modestly affected granular sludge activity and size but markedly compromised granular strength due to calcium loss. Subsequent to the NH4+ shock, the granular strength manifested a significant reduction, as evidenced by a 15-fold increase in protein release from the granules compared to the intact ones. Additionally, NH4+ shock altered the calcium partitioning within the granular sludge, resulting in a decrease in residual calcium and a concomitant increase in bound calcium, further affecting granular strength. This study underscores the overlooked significant phenomenon of NH4+ shock-leaching Ca2+ in anaerobic granular sludge, which warrants significant attention given to its rapid and deleterious effects on granular strength and the shift in calcium state.

Spraying sorbitol-chelated calcium affected foliar calcium absorption and promoted the yield of peanut (Arachis hypogaea L.)

The prevalent use of foliar calcium fertilizers in peanut production is inorganic, but calcium absorbed from the foliar has poor availability. Sorbitol-chelated calcium is a novel organic foliar calcium fertilizer that has rarely been studied for application in peanut production. To explore whether calcium absorption and peanut yields can be affected by foliar application of sorbitol-chelated calcium, this study conducted two field experiments using Virginia peanut (Huayu-22) in 2020 and 2021. The five spray treatments included: deionized water (CK), sorbitol (Sor), calcium nitrate (CaN), a mixture of sorbitol and calcium nitrate (SN), and sorbitol-chelated calcium (SC). The yield of peanuts treated with sorbitol-chelated calcium was increased by 12.31-16.63%, 10.22-11.83%, 6.31-9.69%, and 4.18-6.99% compared to the CK, Sor, CaN, and SN treatments, respectively. Sorbitol-chelated calcium had the lowest contact angle due to the wetting effect of sorbitol, which promoted calcium absorption by leaves. Sorbitol-chelated calcium improved the leaf calcium concentration by 13.12-19.32% and kernel calcium concentration by 6.49-8.15% compared to the CK treatment. Foliar fertilization increased the calcium concentration of each subcellular fraction of leaves and changed the distribution of calcium in mesophyll cells. This change was directly observed by transmission electron microscopy. Additionally, spraying sorbitol alone obtained similar effects to spraying calcium nitrate alone, indicating that the benefits of sorbitol itself were not negligible. The results of the principal component and correlation analysis showed that the increase in calcium concentrations and the change in calcium distribution improved the pod traits of the peanut, thus affecting the peanut yield. The above results showed that from the perspective of calcium absorption and distribution, sorbitol-chelated calcium is a more effective foliar calcium fortifier for peanuts and effectively improves peanut yields.

SfGPX regulates low-temperature tolerance by affecting velocity and intensity of Ca2+ transfer and photosynthetic characteristics in interfered Spiraea fritschiana and overexpressed Spiraea japonica 'Gold Mound'

Genes play regulatory roles in plants' response to low-temperature stress. Our understanding of the mechanism of plants' response to low-temperature stress can be expanded by studying the functions of these genes. SfGPX was cloned from Spiraea fritschiana (S. fritschiana) with the highest low-temperature tolerance, to explore the molecular mechanisms of SfGPX in response to low-temperature stress and the physiological mechanisms involved in the regulation of SfGPX to adapt to low temperature, in two species of Spiraea. SfGPX, which was localized in the cytoplasm, was induced by low temperature. The low-temperature tolerance of Spiraea fritschiana was decreased via the interference of SfGPX, and the low-temperature tolerance of Spiraea japonica 'Gold Mound' (S. japonica 'Gold Mound') was elevated via the overexpression of SfGPX. Under low-temperature stress, the photosynthetic capacity of two species of Spiraea was affected by SfGPX; it was higher in the cold-tolerant plants and lower in the cold-intolerant plants. Under low-temperature stress, the transfer intensity of Ca²⁺ was affected by SfGPX. The transfer intensity of cold-tolerant plants with lower influx level of Ca²⁺ kinetics was weaker than that of cold-intolerant plants. Under low-temperature stress, the transfer velocity of Ca²⁺ was affected by SfGPX, and there were slower effluxes of Ca²⁺ from Ca²⁺ reservoir in cold-tolerant plants than in cold-intolerant plants. The above results indicate that the response of Spiraea to low temperature is regulated by SfGPX through affecting photosynthetic capacity as well as intensity and velocity of Ca²⁺ transfer in response to low temperature in Spiraea.