Effect of Cold Plasma Seed Treatment on Growth and Nitrogen Fixation Traits in Field Pea (Pisum sativum L.) and Soybean (Glycine max L.) Under Cold Stress

Cold stress during early growth can severely impact nodulation, growth, and yield in legumes. This study evaluated cold plasma (CP) seed treatment as a strategy to enhance growth and symbiotic nitrogen fixation (SNF) in field pea (Pisum sativum L.) and soybean (Glycine max L.) under cold stress during early growth. CP-treated and non-treated seeds were grown at 8 °C (cold) or 15 °C (control) for 5 weeks, after which half of the plants were harvested for nodulation and growth assessments. The remainder were transferred to greenhouse conditions until maturity. The cold stress suppressed nodulation and reduced biomass in both legumes. Soybean recovered under greenhouse conditions; however, pea yield remained suppressed. At maturity, SNF traits in both legumes were not significantly affected by early cold stress. CP seed treatment showed little effect under severe cold (8 °C) but at 15 °C, improved root growth in pea and enhanced root and shoot biomass and pod and seed yield in soybean. These findings suggest that CP seed treatment can improve legume performance under moderate cold. However, the current CP seed treatment conditions did not improve the stress resistance of both crops under severe cold stress.