Effect of Different Concentration of NaCl Stress on Growth and Physiological Properties of 2 Species of Callistemon and One Cultivar of C. rigidus ‘Reeves Pink’

In March 2022, 2-year seedlings of Callistemon speciosus, C. austraflora and C. rigidus ‘Reeves Pink’ were potted in Zhoushan, Zhejiang province for recovering. One month later, experiments were conducted on seedlings treated by different concentrations of NaCl (0, 0.20%, 0.40%, 0.60% and 0.80%). 30 days later, determinations were carried out survival rate, biomass, chlorophyll content, proline content, soluble sugar content and antioxidant enzyme activities. The results showed that survival rate, biomass and chlorophyll content of tested seedlings decreased with the increase of NaCl concentration. The survival rate of C. speciosus and C. rigidus ‘Reeves Pink’ treated by NaCl of 0.80% was less than 10.00%, while that of C. austraflora was 27.27%. The activities of SOD and CAT of treated seedlings showed a trend of increase first and then decrease with the increase of salt concentration, while POD continued to increase. The experiment demonstrated that C. austraflora seedling had the highest SOD, CAT, and POD activities. The membership function analysis showed the C. austraflora had the highest membership value, indicating that it had the strongest salt-resistant, suitable for landscape, afforestation and the restoration of salt land.