Assessment of High Temperature Impacts on Early Growth of Garlic Plant (Allium sativum L.) through Monitoring of Photosystem II Activities

Abstract

Garlic (Allium sativum L.), one of the oldest cultivated crops, is the most widely used Allium species belonging to the family Lilliaceae. In this study, growth characteristics, photosystem II activity, and antioxidative enzyme activity were investigated in five temperatures (10-30°C) during early growth stage of garlic to determine the optimum temperature for cultivation and assess the effects of high temperature on early growth of garlic. Vegetative growth (e.g., shoot height, number of leaves) of garlic plants was greater in the temperature ranges of 15-25°C. However, dry weight (of shoot, bulb, and total plant) of garlic was significantly greater at 20°C, compared to either below or above 20°C. Fv/Fo and Fv/Fm values were highest at 15-20°C, and decreased above 25°C. The chlorophyll a fluorescence induction OKJIP transient was also considerably affected by high temperature; the fluorescence yields Fi and F P decreased considerably above 25°C, with the increase of Fk and Wk. Activities of catalase and superoxide dismutase in leaves and peroxidase in roots were high in 20-25°C, and decreased significantly in 30°C. These results indicate that a growth temperature of 30°C inhibits early growth of garlic and that it is desirable to culture garlic plants near 20°C. Fluorescence parameters such a Fv/Fo, Fv/Fm, Fk, ETo/CSm, and PIabs were significantly correlated with dry weight of whole garlic plants (p < 0.01), indicating that these fluorescence parameters can be used for early assessment of high temperature effects even though the damage to the plant is not very severe.