Effects of Silicon on Parameters of Chlorophyll Fluorescence and Ultrastructure of Chloroplast in Aloe vera L.under Salt Stress

Effects of soluble silicon (Si) on parameters of chlorophyll fluorescence and ultrastructure of chloroplast in Aloe vera L. under salt stress were investigated with seven-leaf-old seedlings. Experimental results showed that the responses of aloe to NaCl (100 mmol/L) stress were more evident with prolongation of treatment time; salt injury of 30 d after treatment was more serious than that of 10 d. However, compared with the plants treated with NaCl alone, under NaCl stress with added Si (2.0 mmol/L), the decrease of total chlorophyll content slightly decreased, chlorophyll a content significantly increased, the increase of minimal fluorescence (Fo) and the decrease of variable fluorescence (Fv) were inhibited, and the potential activity of photosystemⅡ (PSⅡ), i.e. Fv/Fo ratio was significantly enhanced. Meanwhile, added Si was favourable to maintain the morphology and structure of aloe chloroplast and to protect the integrity of thylakoid structure,illustrating that exogenous soluble Si alleviates injury of salt stress to photosynthetic organelle and improves photosynthetic efficiency of salt-stressed aloe plant.