Abstract: Effects of soluble silicon ( Si) on parameters of chlorophyll fluorescence and ultrastructure of
chlorop last in A loe vera L. under salt stress were investigated with seven2leaf2old seedlings. Experimental results showed that the responses of aloe to NaCl (100 mmol/L) stress were more evident with p rolongation of
treatment time; salt injury of 30 d after treatmentwasmore serious than that of 10 d. However, compared with
the p lants 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 Siwas favourable to
maintain the morphology and structure of aloe chlorop last and to protect the integrity of thylakoid structure, illustrating that exogenous soluble Si alleviates injury of salt stress to photosynthetic organelle and imp roves pho
tosynthetic efficiency of salt-stressed aloe plant.

Key words: Aloe vera L., Chlorophyll fluorescence, Ultrastructure of chlorop last, Salt stress, Silicon