Studies On Mechanism Of Responce To Salt Stress And Alleviatory Effects Of SA In Chrysanthemum

We studied the Pn and the contents of Na⁺, K⁺, Cl^- of cut flower of chrysanthemum (Dendranthema grandiflora Ramat.)'Jinba'and'Wansheng'under salt stress.Then, in order to gain better insight into the physiological mechanisms of exogenous salicylic acid (SA) on NaCl^-tolerance, the effects of exogenous SA on the growth of shoots, roots, contents of Na⁺, K⁺, Ca²⁺, Mg²⁺ and Pn, respiration and its pathways and activities of plasma membrane H+-ATPase, vacuolar H+-ATPase and H+-PPase of roots of chrysanthemum under salt stress were studied.The results showed as follows:1. The mechanism of responsing to salt stress in chrysanthemum Growth of shoots and roots, changes Na⁺, K⁺ and Cl^- contents in roots, leaves and chloroplasts and net photosynthetic rate of chrysanthemum cultivars'Jinba'(salt-tolerant) and'Wansheng'(salt-sensitive) were studied under 0, 100 and 200 mmol·L-1 NaCl stress. The results showed that fresh and dry weights of both shoots and roots were decreased in both'Jinba'and'Wansheng'compared to controls under NaCl stress. Na⁺ and Cl^- contents increased and K⁺ content decreased with increasing external NaCl concentration and duration of treatment in roots, leaves and chloroplasts of two cultivars. The selectivity of K⁺ abosorption in the leaves and transportation to chloroplasts (CSk, Na) was stronger compared to Na⁺ under NaCl stress in both cultivars. Net photosynthetic rate (Pn) decreased by 52.94% in'Jinba'and 61.04% in'Wansheng'respectively compared to the controls 10 d after 200 mmol·L-1 NaCl treatments. Na⁺ and Cl^- contents in the chloroplasts were significantly negatively correlated with Pn of leaves in two cultivars under salt stress.2. Effects of exogenous salicylic acid on chrysanthemum under salt stress(1) The aim of this experiment was to analyze the alleviation mechanism of exogenous SA on chrysanthemum under salt stress; The effects of salicylic acid (SA) on contents of Na⁺, K⁺, Ca²⁺, Mg²⁺ in roots, leaves and of chrysanthemum and net photosynthetic rate (Pn) were studied with spraying exogenous SA on leaves; The results showed that salt stress increased the content of Na⁺, but reduced the contents of K⁺, Ca²⁺, Mg²⁺ in roots and leaves of chrysanthemum. Exogenous SA treatment increased K⁺, Ca²⁺, Mg²⁺ contents 37.70%, 16.44% and 20.54%, respectively, decreased Na⁺ content 27.13% in the roots; increased the contents of K⁺, Ca²⁺, Mg²⁺ and Pn by 56.52%, 53.23%, 87.53% and 40.74%, respectively, decreased Na⁺ contents 53.41% in the leaves; increased the contents of K⁺, Ca²⁺, Mg²⁺ by 67.97%, 79.40% and 89.32%, respectively, decreased Na⁺ contents by 76.06% in the chrysanthemum at the 10th day after stress treatments. SK, Na, SCa, Na and SMg, Na were also significantly increased by exogenous SA under salt stress. Correlation analysis showed that the Pn has significant negative correlation with Na⁺ and significant positive correlations with K⁺, Ca²⁺, Mg²⁺; These results indicated that exogenous SA may alleviate the damage of chrysanthemum seedlings from salt stress via ion selective absorption and transportation.(2) The objective of this study was to gain better insight into the physiological mechanisms of exogenous salicylic acid (SA) on NaCl^-tolerance in chrysanthemum (Dendranthema grandiflora Ramat.). Effects of exogenous SA on growth of shoots and roots, respiration and its pathways and activities of plasma membrane H+-ATPase, vacuolar H+-ATPase and H+-PPase of roots of chrysanthemum under salt stress were studied with the methods of spraying exogenous SA on leaves of chrysanthemum. The results showed that the growth of shoots and roots of chrysanthemum seedlings were inhibited under salt stress, but it were revived and the accumulation of biomass productions were increased by exogenous SA treatments. Both of total respiration (Vt) and cytochrome pathway respiration (Vcyt) of the roots of chrysanthemum decreased gradually, while alternative pathway respiration (Valt) increased first then decreased later under the salt stress. SA treatments inhibited the scopes of decrease of Vt, Vcyt and Valt of root systems in chrysanthemum induced by salt stress, and at 10th day after stress treatments, the Vt, Vcyt and Valt of exogenous SA treatments increased by 24.22%, 24.47% and 15.77% respectively compared with those of NaCl treatments. The activities of plasma membrane H+-ATPase, vacuolar H+-ATPase and H+-PPase of roots of chrysanthemum decreased respectively under the salt stress, but exogenous SA treatments inhibited the scopes of decrease of the activities of plasma membrane H+-ATPase, vacuolar H+-ATPase and H+-PPase of root systems in chrysanthemum induced by salt stress, and at 10th day after stress treatments, they increased by 24.22%, 24.47% and 15.77% respectively in SA treated plants compared with those in NaCl treated plants. These results indicated that exogenous SA may alleviate the damage of chrysanthemum seedlings from salt stress via improvement Valt rate and activities of proton pump of root systems of chrysanthemum and improve salt tolerance capacity.