Physiological Response of Melon Leaves from Weak Light to Strong Light

PurposeThe study was to explore the effect of the sudden sunny day after continued cloudy days on the growth of melon.

MethodWith Cucumis melo var. makuwa Makino cv.‘Tianbao’ and Cucumis melo var. reticulatus cv.‘Tianshi’ as materials, the physiological indices were observed, including chlorophyll content, carotenoid content, photosynthetic rate, stomatal conductance, intercellular CO₂ concentration, Rubisco activity, antioxidant enzymes (SOD and POD) activities, malondialdehyde (MDA) content, et al., to study the changes of physiological characteristics of leaves in the process of shading recovery (from weak light to strong light).

Result(1) Compared with the control, the carotenoids contents, Rubisco activities, photosynthetic rate and antioxidant enzymes activities showed a tendency of increase, while chlorophyll and MDA contents decreased in the leaves of different melons after removing shade. (2) The different melons showed significant physiological differences, in which ‘Tianbao’ had a strong adaptability to the environment change after removing shade, the carotenoids contents and antioxidant enzyme activities increased rapidly, to protect the cell membrane and photosynthetic organs effectively, and the photosynthetic rate recovered quickly, while ‘Tianshi’ recovered slowly.

ConclusionIn the early spring production, compared with ‘Tianshi’, ‘Tianbao’ had more adaptability to the illumination change.