Semi-lethal high temperature of Chirita heterotricha and its physiological response to high temperature stress

Chirita heterotricha Merr., a perennial herb of genus Chirita(Gesneriaceae), has high ornamental and medical values, but researches on its cultivation and related physiology are lack. The leaf discs in C. heterotricha were treated with different temperatures and the electrolyte leakage rates were measured in order to provide a physiological basis. The correlation was fitted with logistic equation to calculate the semi-lethal high temperature(LT50). After the plants were exposure to the temperature of LT50 for different duration, superoxide dismutase(SOD), peroxidase(POD) activity malondialdehyde(MDA) content, and free proline(Pro) content were assayed. The results showed that the relation of electrolyte leakage rate to temperature was fitted well with logistic equation y = 100/(1 + 17.967e-0.068x), and LT50 was 42.3 ℃. SOD and POD activities were increased at first, and then decreased as the exposure duration extending at LT50, however MDA and Pro contents were continuously increased. The leaves lost water severely after 40 h, and the whole plant wilted and could not recover after 48 h.