Supplementary Calcium Restores Peanut () Growth and Photosynthetic Capacity Under Low Nocturnal Temperature.

Peanut ( L.) is a globally important oil crop, which often experiences poor growth and seedling necrosis under low nocturnal temperatures (LNT). This study assessed the effects of supplementary calcium (Ca) and a calmodulin inhibitor on peanut growth and photosynthetic characteristics of plants exposed to LNT, followed by recovery at a higher temperature. We monitored key growth and photosynthetic parameters in a climate-controlled chamber in pots containing soil. LNT reduced peanut growth and dry matter accumulation, enhanced leaf nonstructural carbohydrates concentrations and non-photochemical quenching, decreased the electron transport rate, increased the transmembrane proton gradient, and decreased gas exchange rates. In peanuts subjected to LNT, foliar application of Ca restored growth, dry matter production and leaf photosynthetic capacity. In particular, the foliar Ca application restored temperature-dependent photosynthesis feedback inhibition due to improved growth/sink demand. Foliar sprays of a calmodulin inhibitor further deteriorated the effects of LNT which validated the protective role of Ca in facilitating LNT tolerance of peanuts.