[Effects of Ca2+ and SA on physiological and photosynthesis of Platycodon grandiflorum under high temperature stress].

In order to reveal feasibility of different concentrations of Ca2+ and SA on Platycodon grandiflorum under high temperature stress, the effects of Ca2+ on physiological index and related photosynthetic parameters were studied. Pot cultured P. grandiflorum leaves under the same outdoor conditions were sprayed with CaCl2 and SA separately, and then placed in the high incubator [35 degrees C/25 degrees C (day/night), light intensity 3 600 lx], and sprayed with distilled water at 25 degrees C and under high temperature stress were set as the control. The related photosynthesis, relative conductivity, contents of proline, malondialdehyde, soluble protein, activities of SOD and CAT, ASA and GSH content were measured. The results show that the 6 mmol x L(-1) CaCl2 and 1.5 mmol x L(-1) SA enhanced the activities of SOD and CAT, the contents of proline and soluble protein, and effectively reduced the damage of heat stress on cell membrance. At the same time, the exogenous Ca2+ and SA increased the contents of chlorophyll and carotenoid, the efficiency of leaf photosynthesis and ASA and GSH content, and thus effectively resisted the oxidative stress caused by high temperatures, but with the increasing concentration of spraying, P. grandiflorum decreased the ability to resist high temperature stress. In conclusion, the foliage spraying CaCl2 and SA could reduce the damage of high temperature stress on P. grandiflorum leaves.