Abating Effect Of Nitrate On Seawater-Stress Of Catharanthus Roseus Seedlings

In the green house,pot experiments were conducted to study the effects of nitrate on growth and physiological characteristics of Catharanthus roseus seedlings under different concentration of seawater (10%,20%,30%and 40%).The results showed that:(1) The FW(fresh weight) and DW(dry weight),total nitrate and leaf chlorophyll content of Catharanthus roseus with 10%seawater were higher than control,the treatment of high density seawater remarkably inhibited Catharanthus roseus growth,the trends of FW(fresh weight) and DW(dry weight), total nitrate and leaf chlorophyll content increased with increasing of exogenous nitrate concentration; high concentration of seawater resulted in the decreasing of led to root vigor of Catharanthus roseus seedlings,the application of nitrate(15.0mmolL^-1) increasd the root vigor of Catharanthus roseus.(2) Under 10%seawater,the photosynthetic rate,transpiration rate and water use efficiency of Catharanthus roseus with 10%seawater were higher than that of control,and there were slight changes of stomatal conductance and the internal CO₂ concentration treated with 10%seawater;with the increasing of seawater concentrations,the photosynthetic rate,transpiration rate,stomatal conductance and water use efficiency in leaves of seawater-stressed Catharanthus roseus were significantly decreased, and the internal CO₂ concentration significantly increased;with the increasing of exogenous the concentration of nitrogen under the same seawater concentration,the photosynthetic rate,transpiration rate,stomatal conductance and water use efficiency were all significantly increased,and the internal CO₂ concentration significantly decreased.(3)The activities of SOD(surperoxide dismutase),POD(peroxidase),CAT(catalase) in leaves of seawater-stressed Catharanthus roseus were significantly increased,with the increase of the concentration of nitrogen under the same seawater concentration,the activities of SOD(surperoxide dismutase),POD(peroxidase),CAT(catalase) were further increased. (4)In the different-site of Catharanthus roseus seedlings,K⁺,Ca²⁺ content were all improved by the application of nitrate,whereas the content of Na⁺,Cl^- were restrained in some extent at the same time.K⁺/Na⁺ and Ca²⁺/Na⁺ were enhanced by the application of nitrogen under seawater stress;the capability of selective absorption K⁺ is leaf＞stem＞root.The MDA(malondialdehyde) and ELP electrolytic leakage percentage) in leaves of seawater-stressed Catharanthus roseus were significantly increased,with the increase of the concentration of nitrogen under the same seawater concentration,the MDA and ELP were significantly decreased.