Studies On The Heat Resistance Of Six Dendranthema Mums

Chrysanthemum {Dendranthema grandiflorum),a traditional flower in China, is popular cultivation for its rich cultivars and varied colors. The cool climate is adaptable to it, but lasting high temperature would potentially make a tremendous injury, and result that their ornamental values reduce and restrained of their applied regions. With the aim of providing simple and applied methods for the identification of chrysanthemum's heat resistance, and offering scientific basis for the application of chrysanthemum in high-temperature area, six species and cultivars of Dendranthema were used as materials in this study, and couple of indexes, such as the relations between the heat resistance and the appearance, leaf anatomic structures, physiological and biochemical changes under heat treatment ,were studied. The changes of POD isozyme bands and soluble protein in leaves were also studied.The main results were shown as follows:1. The heat injury indexes had the remarkable difference between six materials under the hot field conditions. D.nankingense and D. morifolium 'PenJing II 'are heat-tolerant, but D. indicum van aromaticum isn't. The result was in accord with the field observations.2. Observations of chrysanthemum's appearance and leaf anatomy indicated that: The leaf epidermal hair of D.nankingense is the most in 6materials.The leaf of D. morifolium 'PenJing II 'is small and dense, and the number of its stomata is the most. The leaf of D. indicum van aromaticum is big and thin, and the number of its stomata is the least.3. Results of the leaf physiological and biochemical changes showed that: It is a gradual process that chrysanthemum adapts to heat treatment. The index of 24h treatment at 40C may reflect mum's heat resistance better. The content decrease of soluble protein and the increase of electrolytic leakage in heat-tolerant chrysanthemum were weaker than that in heat- sensitive ones.4. Eight physiological and biochemical indexes were treated by using principal component analysis and subordinative function. The comprehensive value of mum's heat resistance was obtained and evaluated. The best regressive function was founded to forecast other mum's heat resistance. (D=l. 277-0.145X1-0.126X2-0.104X4+0. 532X8)5. Changes of POD isozyme in different mum's leaves under heat treatment were studied. The isozyme bands in D.nankingense and D.morifolium 'PenJing II' were steadiest among 6 materials, which was opposite to the change in D. indicum var. aromaticum. Perhaps the isozyme (Rm=0.66) plays a key role in enhancing mum's heat resistance.6. Changes of soluble protein in chrysanthemum's leaves were analyzed by using sds-page. More than 10 smHSPs were observed , 15-30kD HSP was in the majority among them. The amount of HSP induced by l-2h heat treatment increased. Some of them disappeared after 4-6h heat treatment. Perhaps the amount and the existing time of HSP have a certain relation to the heat resistance of chrysanthemum.