The Relationships among Chlorophyll Fluorescence Parameters and Chloroplast Antioxidant Enzymes in Puccinellia tenuiflora Seedlings under Na2CO3 Stress

摘要

The relationships among chlorophyll fluorescence parameters, chloroplast antioxidant enzyme and active oxygen in the leaves of P. tenuiflora seedlings under Na2CO3 stress was investigated in the article. Results showed that when Na2CO3 stress was less than 0.4%, the activity of antioxidant enzymes (APX、GST、SOD) increased along with the increasing Na2CO3 stress. However, the changes of actual photochemical efficiency of PSII in the light (ΦPSII), photochemical quenching efficiency (qP), electron transfer rate (ETR) and heat dissipation rate (HDR) were not obvious. When Na2CO3 stress was over 0.4%, ΦPSII, qP, ETR and HDR increased with the increasing Na2CO3 stress, while the active oxygen and antioxidant enzyme activity of chloroplast decreased. All this suggest that there is refined osmotic regulation mechanisms may exist in the P. tenuiflora seedlings when Na2CO3 stress was below 0.4%, and these mechanisms ensure that the photosynthesis can be successfully completed. Chloroplast is quite sensitive to salt stress, Na2CO3 stress below 0.4% resulted in the increase of active oxygen and accordingly induced defend reactions in the chloroplast. When Na2CO3 stress was over 0.4%, the surplus light energy might probably dissipate through the following two ways: one is increasing heat dissipation rate(HDR); The other is enhancing pesudocyclic photophosphorylation by increasing ΦPSII and ETR. Different mechanisms might exist in this kind of plants to adjust the absorption and utilization of light energy under various Na2CO3 stress.