Physiological responses and drought resistance evaluation of forage oat ( <i>Avena sativa</i> L.) seedling cultivar under drought stress

Oat (<i>Avena sativa</i> L.) is an important forage crop widely used in animal husbandry. However, the greenhouse effect, which leads to increasing global temperatures, extreme water scarcity, and more frequent drought events, also creates abiotic stress that inhibits oat growth. Drought stress strongly affects the yield and quality of forage oats, hindering the selection, promotion, and utilization of drought-resistant cultivars. This study investigated alterations in the growth and physiological traits of diverse oat cultivars under drought stress for varying durations. We comprehensively assessed the drought resistance capabilities of each variety. Forty oat cultivars were subjected to drought stress starting from plant growth up to the two-leaf stage a pot-based water withholding method. The stress durations were 0 d, 7 d, and 14 d. Compared with those of the control, the key physiological parameters of the test cultivar decreased with increasing drought stress duration. These factors increased the maximum photochemical quantum yield (Fv/Fm), PS II quantum efficiency (Fv/Fo), soil plant analysis development (SPAD) value, net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs). Conversely, the malondialdehyde (MDA) and proline (Pro) contents increased. Antioxidant enzyme activity initially increased but subsequently decreased. Changes in osmoregulatory substance content and the modulation of antioxidant enzyme activity are key components of drought resistance mechanisms. Therefore, Fv/Fo, Pro, Tr, Gs, and Pn have emerged as reliable parameters for assessing drought resistance in forage oat seedlings. When assessing seedling drought resistance using biochemical parameters such as photosynthesis, a comprehensive analysis combining multiple indicators and methods is essential. This study provides a theoretical basis for screening drought-resistant oat cultivars and for high-yield cultivation practices.