Heat-stress-induced changes in enzymatic antioxidant activities and biochemical processes in bell pepper (Capsicum annuum L.) seedlings

Heat stress (HS) is expected to become a significant abiotic stressor with the continued rise in global temperatures, severely limiting the development and production of bell pepper (Capsicum annuum L.), especially in arid and semiarid regions. Thus, this study looked into the impact of HS on the antioxidant activity, as well as the biochemical responses of bell pepper seedlings under varying temperatures (40, 32, and 25 degrees C) for 5 days. The results showed that exposure to higher temperatures led to an increase in enzymatic and antioxidant processes. At 40 and 32 degrees C, HS led to a decrease in chlorophyll a (4.327 mg g-1 FW), b (1.710 mg g-1 FW), total chlorophyll (5.202 mg g-1 FW), and total carotene (1.092 mg g-1 FW) compared to the control at 25 degrees C (chlorophyll a 5.383 mg g-1 FW, chlorophyll b 2.358 mg g-1 FW, total chlorophyll 6.692 mg g-1 FW, and total carotene 1.817 mg g-1 FW). On the other hand, seedlings exposed to 32 and 40 degrees C showed higher antioxidant activity and 2,2 '-azino-bis-(3-ethylbenzothiazoline-6-sulfonic) acid radical scavenging activity compared to the control group, as the activity significantly increased in response to high temperatures. Similarly, the catalase activity also significantly increased in response to 40 and 32 degrees C compared to the control group at varying temperatures. The proline content of the stressed seedlings increased at 32 and 40 degrees C compared to the control at all temperatures. These results indicate that HS damages the antioxidant activity, biochemical processes, and growth of bell pepper seedlings; thus, a scientific approach is needed to mitigate the effects in arid regions like Qatar.