Abstract: An in situ measurement of light intensity was conducted in the Sonnerratia apetala plantations under different environmental conditions, and the eco-physiological responses of the S. apetala seedlings to different light intensities were studied. The seed germination rate and the seedling’s eco-physiological parameters of S. apetala all decreased with the increasing level of shading. At 80% and 40% of full light, the stem height, basal diameter, node number, and lamina number of seedlings decreased to some extent; while at 20% of full light, the seedling’s growth was seriously restricted. At weak light intensity, the germination rate was very low, and the eco-physiological parameters such as chlorophyll content, net photosynthetic rate, soluble sugar contents, and nitrate reductase activity decreased, with significant differences to those at strong light intensity. Therefore, low light intensity could be the main reason for the low level eco-physiological parameters and high death rate of S. apetala seedlings. The natural regeneration and dispersal of S. apetala and the techniques for S. apetala forestation were also discussed.

Key words: Humic acid compound fertilizer, Pepper, Application rate, Mechanism of anti-senility and incremental yield