Integrated Assessment of Drought, Saline, and Alkaline Stress Responses During Seed Germination of Sesamum indicum L. Using PCA and Membership Function Analysis

Soil salinization, alkalization, and drought increasingly threaten crop establishment in arid regions. This study evaluated the effects of drought, salt, and alkali stress on the germination and early growth of Sesamum indicum L. to identify tolerance differences among these stresses. Four osmotic potentials (−0.09, −0.17, −0.23, and −0.34 MPa) were established using polyethylene glycol (PEG 4000) to simulate drought, NaCl to induce salt stress, and Na₂CO₃ to represent alkali stress, with distilled water as the control. Low salt stress (−0.09 MPa NaCl) did not significantly affect germination, whereas higher stress levels (−0.34 MPa) under all treatments markedly suppressed germination. Among the three stresses, Na₂CO₃ caused the strongest inhibition. The germination index decreased progressively with declining osmotic potential, while the average germination time increased by one to two days compared with the control. Drought, salt, and alkali stresses also restricted seedling growth, though mild salt and drought stress slightly enhanced dry matter accumulation before severe inhibition occurred. Principal component analysis and membership function evaluation classified sesame responses into three tolerance categories: high, moderate, and sensitive. The combined analysis indicated that sesame exhibits greater tolerance to salt stress than to drought or alkali stress. Overall, Sesamum indicum adapts to mild osmotic stress by sustaining germination and nutrient mobilization, but higher stress levels disrupt germination dynamics and seedling development. These findings provide a comparative framework for screening sesame genotypes suited to saline environments and for improving stress-resilient cultivation strategies.