Alleviative effects of LaCl3 on simulated acid rain stresses for Cucurbita pepo seedlings

Using Cucurbita pepo as the experimental material, the alleviative effects of foliar surface spraying for LaCl3 (12 mg/L) on seedling growth and three physiological indexes of C. pepo were investigated under some simulated acid rain (SAR) stresses. Results show that the damage effects of SAR on C. pepo seedlings are alleviated by the LaCl3 treatment. The fresh weights of the seedlings treated with LaCl3 solutions of pH 3.5 and pH 3.0 are significantly higher than those of the treatments only with SAR, and are equivalent to 94.7% and 78.6% of the control level (pH 6.5). However, no significant differences are observed between the treatment with other SAR+LaCl3 solution and the treatment only with SAR. The chlorophyll and dissolved protein contents follow the trend of the seedling fresh weight, and the indexes treated with pH 3.0 and pH 3.5 SAR+LaCl3 solutions are higher significantly than that treated only with SAR, but the differences of pH 3.0 are slightly greater than those of pH 3.5. Compared with the control, the dissolved protein content treated with pH 3.5+LaCl3 solution is the highest. The proline content increase consistently with the pH value, and improved by the LaCl3 treatment. The proline contents treated with pH 3.5 and pH 3.0 SAR+LaCl3 solution are higher significantly than that treated only with SAR. Therefore, the alleviative effects of LaCl3 on middle SAR stresses for C. pepo seedling are significant.