Effects of Seawater Irrigation on Several Physiological Characteristics of Coconut Seedling Leaves

QIN Chengying1) CHENG Wenjing1) TANG Longxiang⒉,3)(1 College of Agriculture,Hainan University,Danzhou,Hainan 571700; 2 Coconut Research Institute,CATAS,Wenchang,Hainan 571339; 3 Hainan Key Laboratory for Research of Tropical Palm Plants,CATAS,Wenchang,Hainan 571339)

coconut seedling;seawater irrigation;physiological parameter

A pot experiment was carried out with two coconut cultivars(Hainan Tall,Wenye 2 Dwarf) seedlings irrigated with different dilutions of seawater for 60 days in order to investigate the effects of salinity stress on several physiological parameters,such as leaf relative water content(LRWC),leaf proline,malondialdehyde(MDA),soluble sugars(SS),K+,Na+ contents and K+/Na+ ratio.Results revealed that both the two coconut seedlings grew well,irrigated by low concentration seawater(30%).All physiological parameters expect MDA had no obvious significance compared with control groups.However,the indexes became more obvious along with the seawater concentration increased.The high salinity stress affected negatively both the cultivars.LRWC,K+/Na+ ratio decreased obviously,Proline,SS and Na+ content increased apparently in both cultivars.Hainan Tall had more increase in Na+ content and decrease in K+/Na+ ratio.Whereas there were more reduction of RLWC and more addition of SS in Wenye 2 declined more dramatically,SS increased more quickly compared with Hainan Tall.Changes of Proline had similar trend.The variation of MDA was complex in both cultivars,which ascended firstly,then declined and ascended again.