Antioxidant Responses of Cucumber (Cucumis sativus L.) Plant to Heat Stress

Abstract

The aim of this this study is to study the antioxidant responses of cucumber (Cucumis sativus L.) cultivar, Beith Alpha F1, under heat stress (45 °C and 55 °C, 4 hours). Cucumber plants were grown in plastic pots containing perlite in the climate chamber for ten days and irrigated with Hoagland nutrient solution. Plants were harvested 24 hours after high temperature application. The amount of chlorophyll-a, chlorophyll-b and total chlorophyll in the cotyledons of the cucumber plant gradually decreased with the increase in temperature. Superoxide dismutase activity induced by high temperature in cucumber cotyledons indicates that the superoxide radical is effectively detoxified. Low ascorbate peroxidase and high glutathione reductase activity in cotyledons at high temperature conditions indicate that the ascorbate-glutathione cycle is inhibited. However, heat stress did not lead to the accumulation of H2O2 in cotyledons. In addition, lower level of malondialdehyde in the cotyledons showed that membrane systems were not chemically damaged under heat stress. Accordingly, it could be concluded that superoxide radical accumulation did not occur in the cotyledons of cucumber and catalase was the predominant H2O2-detoxifying enzyme under heat stress. In addition, membrane systems in cucumber cotyledons may be physically affected by high temperature applications.

Keywords

• antioxidant system
• cucumber
• cucumis sativus
• heat stress
• heat tolerance