Study On Heat Resistance Of Chrysanthemum Floral Organ And Effects Of Exogenously Nitric Oxide On Heat Resistance Of Chrysanthemum

The chrysanthemum(Chrysanthemum morifolium), an important cut and pot flower world wide, has high ornamental and economic value. High temperatures during the summer months represent a problem for the cost and ornamental quality of chrysanthemum. To screen strong heat-resistant cultivars and enhance chrysanthemum heat resistance could provide scientific basis in its popularization and application. In this paper, physiological characteristics of four summer chrysanthemum cultivars'Zao Huang','Chang Zi','Feng Yunli'and 'Nan nongyudie'at pigmented, initial and full flowering stages were studied and screened heat-resistance index. Effects of exogenously NO on physiological characteristics of heat stressed chrysanthemum cultivar'Zao Huang'at growth and flowering stages were studied to discuss physiological mechanism in the improvement of heat resistance. The main findings are as follows:(1) Eight physiological and biochemical indexes were treated by using main component analysis and correlation analysis, and four parameters i.e. SOD activity (X1), GSH content (X4), protein content (X6) and proline content (X7) were screened as heat tolerance indexes. The best regressive function founded to forecast other mum's heat resistance was D=0.696+(0.402X1+0.296X4+0.834X6-1.612X7) x10-3.(2) The decrease of heat tolerance of floral organ at three flowering stages was initial flowering stage, full flowering stage and pigmented stage. Pigmented and full flowering stages were more reliable to heat resistance evaluation of chrysanthemum's floral organ. The decrease of heat tolerance of four chrysanthemum cultivars was'Zao Huang','Feng Yunli','Chang Zi'and'Nan nongyudie'. Compared with three other cultivars, epidermal cells of'Zao Huang' ray florets were smaller and more closely arranged.(3) NO could maintained a higher level of chlorophyll, carotenoid, Pn and PSII activity in heat stressed chrysanthemum seedlings sprayed with SNP, compared to distilled water ones. This revealed that NO could modulate photosynthesis in chrysanthemum, and increase heat tolerance by enhancing photosynthesis.(4) NO had obviously protective effects on leaves and ray florets oxidative damage in heat stressed chrysanthemum. Compared to the control, NO content and activities of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbic acid peroxidase (APX) were increased significantly in chrysanthemum plants applied with SNP, while superoxide anion (O2-) produciton activity, hydrogen peroxide (H2O2) and malondialdehyde (MDA) content were decreased significantly. NO acted as an important signal molecule, might alleviate lipid peroxidation through activating antioxidant enzyme system to improve heat resistance of chrysanthemum.