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Abstract

Plants produce and accumulate reactive oxygen species (ROS) when exposed to stress conditions. To counteract the harmful effects of these molecules, plant cells employ an antioxidant defense system composed of both enzymatic and non-enzymatic components. This research examined how desiccation influences the activities of major oxidative stress enzymes, Peroxidase (POD), Catalase (CAT), and Polyphenol oxidase (PPO), as well as Glucose-6-phosphate dehydrogenase (G6PDH), a key enzyme in the oxidative pentose phosphate pathway, in the seeds of Afzelia africana Sm. and Chrysophyllum albidum (Linn.). Mature seeds of both species were collected directly from parent trees and desiccated under ambient laboratory conditions for 0, 3, 7, 10, 13, 15, 22, and 35 days. Seeds were assayed for enzyme activity at each interval. In A. africana, maximum germination (90.00%) occurred after 15 days of desiccation at 4.86% moisture content, whereas germinability of C. albidum declined by more than 50% after 7 days at 9.02% moisture. G6PDH activity in A. africana increased significantly (P ≤ 0.05) up to day 7 and again on day 35, while C. albidum exhibited a peak on day 15 followed by a marked decline. Peroxidase activity decreased during early desiccation in A. africana but increased in C. albidum until day 10, whereas catalase activity rose significantly at later stages in both species, remaining higher in C. albidum. PPO activity showed no significant interspecific differences. Overall, A. africana (orthodox) maintained an enhanced oxidative stress enzyme activities during desiccation, while C. albidum (recalcitrant) displayed reduced enzymatic responses. These findings highlight the role of antioxidant enzymes in sustaining cellular integrity under water deficit and provide insight into the physiological basis of desiccation tolerance in tropical tree seeds.

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