关键词: 子叶丢失强度, 子叶丢失时间, 养分供应, 碳水化合物, 苗木生长状况

Abstract: [Objective] Cotyledon loss of Quercus variabilis in autumn and the following spring after emergence is a common phenomenon in the nature. This study was designed to simulate the interaction of two loss phenomena, and investigate the additive effects on seed reserves translocation and seedling growth, and reveal the mechanism of animal predation on the regeneration of Q. variabilis seedlings. [Method] In this experiment, the Quercus variabilis seeds were used as experimental material, and two factor split plot design was employed. The cotyledon distal was excised before sowing, to simulate cotyledon loss in three intensities (main factor) in the autumn, without feeding (intact seeds), 1/3 feeding (mild) and 2/3 feeding (severe). After seeds emergence, the cotyledon were removed dynamically, to simulate cotyledon loss time (side factor) in the following spring (acorns removal on 4, 8, 12, 16, 20, 25, 30 days after emergence). At the same time, no acorn was removed served as the control to simulate cotyledon no-feeded by animals in spring. Seed nitrogen and carbohydrate content were measured dynamically to analyze the pattern of seed transfer to seedling. Seedlings survival rate, growth, nutrient accumulation and non-structural carbohydrate of Q. variabilis were measured at the end of growing season. [Results] 1) In 30 days after seedling emergence in speing, the translocation rate of starch was (72.4%-89.36%), soluble sugar (66.61%-72.72%), and nitrogen (30.64%-59.45%). 2) The translocation of nitrogen from intact seeds to seedlings was completed in 25 days after seed emergence, and the time for the nitrogen transfer from cotyledon lost seeds in autumn to seedlings was significantly shortened (8d). 3) The main effects indicated that the loss of 2/3 cotyledon in autumn caused the height and diameter of the seedlings to decrease by 30% and 18%, respectively. The side effects indicated that cotyledon loss before emergence 20 days could depress seedling growth at the following spring. 4) The interaction effects indicated that for the treatment of cotyledon removal in 4 days after emergence and the intact seeds in autumn, the survival rate was only 36.3%, and biomass decreased by 78.2%. the cotyledon removal in 25 days after emergence could depress the nutrient and carbohydrate accumulation. For treatment of cotyledon removal by 1/3 in the autumn, and cotyledon removal in 4 days after emergence in the following spring, the survival rate decreased by 65.2%. And the cotyledon loss in 25 days after emergence had almost no effect on seedling growth and nutrients accumulation. The treatment of cotyledon loss by 2/3 seeds in the autumn significantly inhibited the seedling growth regardless of the cotyledon removal or not. [Conclusion] The effect of cotyledon loss on seedling growth in the following spring was not only determined by the loss time, but also by the loss intensity in autumn. Therefore, the additive effects between cotyledon loss intensity and time should be fully considered, which is of great significance for revealing the regeneration mechanism of Quercus variabilis.

Key words: cotyledon loss intensity, cotyledon loss time, nutrient supply, carbohydrate, seedling growth condition