Seasonal Comparative Analysis of Proline Accumulation in Two Species of Genus Euphorbia

Abstract

Proline accumulation is an important physiological response that helps plants tolerate environmental stress. The present study estimated seasonal and organ-specific variations in free proline content in Euphorbia indica and Euphorbia microphylla growing in the semi-arid region of Chittorgarh, Rajasthan. Root, stem, and leaf samples were collected during the rainy, summer, and winter seasons, and proline concentration was estimated using the ninhydrin colorimetric method. Clear seasonal differences in proline accumulation were observed in both species, although the patterns differed. In Euphorbia indica, mean proline content increased from the rainy season (38.08 µg g⁻¹ DW) to summer (57.60 µg g⁻¹ DW) and reached its maximum in winter (75.83 µg g⁻¹ DW). The highest organ-specific values in this species were recorded in leaf tissue during summer (84.88 µg g⁻¹ DW) and in stem tissue during winter (98.45 µg g⁻¹ DW). In Euphorbia microphylla, the highest seasonal average was recorded during the rainy season (86.01 µg g⁻¹ DW), followed by summer (82.99 µg g⁻¹ DW) and winter (77.03 µg g⁻¹ DW). Root tissues showed high proline levels during the rainy and summer seasons, whereas leaf tissue showed the highest value during winter (98.03 µg g⁻¹ DW). Overall, Euphorbia microphylla maintained higher proline levels than Euphorbia indica during the study period. The findings indicate species-specific and organ-specific seasonal variation in free proline accumulation and support its use as a biochemical indicator of seasonal physiological adjustment in Euphorbia species under fluctuating environmental conditions.