Abstract: The effects of heat and drought on growth and respiration in pepper (Capsicum annuum L.) were studied. Heat stress resulted in a growth reduction in cultivar of Jizhao×Jilin, but not in Zhengjiao No.13. Drought, especially drought under heat, significantly inhibited the growth of peppers. Drought also increased the ion leakage from leaves more than heat and heat strengthened the injury of drought to peppers, which was more seirous observed in Jizhao×Jilin than Zhengjia No.13 did. Heat induced increases both in total, cytochrome and alternative pathway respirations, while drought strongly decreased cytochrome respiration, but increased alternative respiration. Cross effect from both drought and heat strongly decreased both total and cytochrome respirations, however, alternative respiration increased significantly at the initial 1d and then decreased sharply. Zhengjiao No.13 showed higher alternative and total respirations than Jizhao×Jilin under heat or/and drought stresses. These results suggest that higher heat or/and drought tolerance of pepper is associated with the capacity to keep high total and alternative respirations under stresses.

Key words: heat and drought stresses, growth, respiration, Capsicum annuum L.