Effects of High Temperature on the Physiological and Antioxidation Abilities of Cucumber Seedlings

Abstract

When cucumber plants (Cucumis sativus L.) are subjected to high-temperature environments (>35°C), their physiological structures are disrupted, affecting male–female flower inflorescence and fruit shapes, which are critical to cucumber quality. Accordingly, selecting heat-resistant cultivars is imperative in cucumber cultivation. This study tested three cucumber cultivars with varying resistance levels to high temperature: Wen nong 210, CU-127, and Ks No. 3. When the seedlings of these cultivars grew their primary leaves, leaf discs were collected and treated at varying temperatures; subsequently, relative injury (RI) was calculated to determine the cultivars’ cell membrane stability at high temperatures. The results revealed that Wen nong 210 sustained 50% RI at 54.1°C, exhibiting the greatest cell membrane stability, followed by CU-127, which sustained 50% RI at 53.9°C, and then Ks No. 3, which sustained 50% RI at 52.8°C. Analyzing the cultivars’ physiological indices indicated that, at 45°C, Ks No. 3 had the highest malondialdehyde (MDA) content but the lowest chlorophyll content, whereas Wen nong 210 had low MDA content but high chlorophyll content. Antioxidation analysis showed that at 45°C, Ks No. 3 and Wen nong 210 exhibited the lowest and highest ascorbate peroxidase (APX) activity, respectively. Furthermore, at 35°C, Ks No. 3 exhibited high proline content. In summary, physiological indices (H2O2, MDA, and chlorophyll content), proline content, and APX activity can constitute the basis of heat resistance screening standards for cucumber plants grown under high-temperature conditions.