The Compound Effects of N and Zn on Chloroplast Ultrastructure of White Clover Leaves

Sand culture experiment were carried out to investigate the compound effects of N and Zn on chloroplast ultrastructure of white clover leaves. The main findings showed that the dry matter weight, chlorophyll content of leaves significantly decrased with the increased N rate in Zn deficiency. Therefore, N and Zn combined application showed antagonism effect in the condition of Zn deficiency. However, in the condition of Zn sufficiency, the dry matter weight, chlorophyll content of leaves were higher in middle N rate than in high and low N rate. Consequently, N and Zn combined application showed synergism effect. Nevertheless, when high amount of N supply, the dry matter weight, chlorophyll content of leaves significantly decrased compared with middle and low N rate. Therefore N and Zn combined application showed antagonism effect. The ultrastructure of chloroplast of mesphyll cell of white clover leaves showed that in the condition of Zn deficiency, with the increasing rate of applied N, the inner structure of chloroplast ruined, in which the number of the grana and grana lamellae as well as stroma lamellae decreased and disintegrated, which resulted in the declination of photosynthesis capacity of chloroplast. In the condition of sufficient supply of Zn, the number of the grana, grana lamellae and stroma lamellae as well as the order of the combination of them in chloroplast were the highest at middle rate of N applied. However, the volume of chloroplast reduced and the system of lamellae swelled and couldn'n form grana when high rate of applied N. The changes of ultrastructure of chloroplast were correspondence with the changes of chlorophyll content and dry matter weight.