The Seedling Growth and Physiological Traits of Different Oat Varieties' Response to Alkaline Stress

ABSTRACT Salt and alkaline stress negatively affect the growth, physiology and yield of crops in saline‐alkali soil. To date, more studies have focused on crop response to salt stress, but fewer studies have concentrated on the alkali stress on crop production, so that the physiological mechanisms of plants' response to alkali stress are still unclear. In this study, 15 oat varieties were tested for alkali tolerance under four Na 2 CO 3 treatment levels (0, 10, 20 and 40 mM Na 2 CO 3 solution). The growth characteristics and physiological mechanisms of oat seedlings under alkali stress were investigated, and their alkali tolerance was comprehensively evaluated using methods such as principal component analysis. The results showed that Na 2 CO 3 stress significantly inhibited the plant height, root length, stem diameter, total root volume and total root surface area of oat seedlings, with the degree of inhibition increasing with higher alkali stress concentrations ( p < 0.05). The activities of peroxidase (POD), superoxide dismutase (SOD), catalase (CAT) and the malondialdehyde (MDA) content in oat seedling leaves generally increased with increasing alkali concentrations. On the basis of growth and physiological characteristics, the alkali tolerance threshold for oats was identified as 10 mM Na 2 CO 3 . Moreover, principal component analysis and membership function methods were used to comprehensively evaluate alkali tolerance across indicators, identifying strongly tolerant varieties such as Hammer (V1), Monica (V4) and Tyke (V6) and weakly tolerant varieties such as Baiyan 2 (V5) and Apollo (V12). The present investigation comprehensively evaluated the alkaline tolerance of different oat varieties by integrating above‐ground phenotypic and below‐ground root morphological indicators, providing technical support for the breeding of alkali‐tolerant forage crops.