Research On The Salt Tolerance Difference Of Three Ground Cover Plants And The Alleviative Effects Of The Exogenous Calcium On The Salt Stress

Three ground cover plants Vinca major cv.‘Variegata',Nepeta cataria and Viola prionantha grown in pots were treated with Na Cl and Ca Cl2 so that some indicators of treated plants including plant increment,salt injury rate and index,MDA and solute protein and solute sugar contents,SOD and POD activities and net photosynthetic rate(Pn)were investigated,aiming at understanding the differences between the three plants in salinity tolerance and the effects of Ca Cl2 on salt stress and the suitable concentration that is available in application of Ca Cl2.The results showed that with increasing concentration of the salt treated,growth rate of the plant height increased at the beginning and then decreased and salt injury rates and indexes kept a trend to grow,with the biggest relative growth rate for Vinca major cv‘Variegata'and the largest increasing range for Nepeta cataria in salt injury rate and index,and the MDA contents of Variegata and Nepetacataria had a trend to increase,with small MDA variance for Viola prionantha,and the root and POD activities of Viola prionantha and Nepeta cataria increased firstly and then decreased.The root activity of Vinca major cv‘Variegata' was very significantly lower than that of the control and its POD activity had no significant variance during the salt treatment.The SOD activity of the three plants had no significant variance,while the Pn of ‘Variegata' and Viola prionantha increased firstly and then decreased but the Pn of Nepeta cataria kept a trend to decrease under salt stress condition.When ‘Variegata' was applied with Ca Cl2 in concentration of 10 mmol·L-1 or Nepeta cataria and Viola prionantha in concentration of 20 mmol·L-1,the growth and relative growth of three tested plants were significantly higher and the salt injury index of them was significantly or very significantly lower than that of the control.The Pn of three plants treated with 10 mmol·L-1Ca Cl2 appeared the largest value in all.The other indexes investigated showed irregular variance under different concentrations of Ca Cl2.Based on the indexes analyzed and the membership function results,the salt tolerance ability of the three plants was ranked as Viola prionantha >Vinca major cv‘Variegata'> Nepeta cataria.The Ca Cl2 treatment had more obvious alleviating effects on the plants under middle lower salt stress(3mg·g-1,4mg·g-1),with no obvious effects under higher salt stress(5mg·g-1~7mg·g-1).The appropriate concentrations of Ca Cl2 applied for Viola prionantha and Nepeta cataria,and Vinca major cv‘Variegata' were 20 mmol·L-1 and 10 mmol·L-1 respectively.