Shading reduced the compensation and enhancement effects of soil nutrition on the growth of cotyledon-damaged Quercus acutissima seedlings

Background and aims Cotyledons are important nutrient sources for seedling establishment in seed plants, however, the acorns are often consumed by rodents and/or insects. This study aimed to examine the compensation or enhancement effect of soil nutrient for cotyledon damage on seedlings of Quercus acutissima under different light conditions. Methods We simulated three levels of predation (no damage; mild damage, excised 1/3 of cotyledons from the distal end and severe damage, excised 2/3 of cotyledons from the distal end), two soil nutrient contents (high and low nutrient) and two light intensities (high and low light) in a greenhouse experiment. Seedling survival rate, height, stem basal diameter, specific leaf area, chlorophyll concentration, leaf gas exchange, leaf nitrogen and phosphorus concentration, leaf number, total and partitioned dry biomass were determined. Results Cotyledon damage had detrimental effects on height, stem basal diameter, dry weight, leaf number and net photosynthetic rate of the seedlings under high light condition. When soil nutrient was supplemented, the impact of cotyledon damage on the growth of seedlings was alleviated, which indicated the compensation or enhancement effect of soil nutrient on cotyledon damage. However, the compensation or enhancement effect was light-dependent, and was reduced under low light conditions. Conclusions Soil nutrients could partially replace the role of cotyledons in the growth and development of Q. acutissima seedlings, but shading reduced the compensation or enhancement effect of soil nutrients. Therefore, cotyledons are especially vital for seedling regeneration in nutrient-poor soil environment, particularly in low light intensity conditions.