Effect of Organic Acids on Biomass and Physiological Characteristics of Malus hupehensis Seedlings Under Continuous Cropping Effect of Organic Acids on Biomass and Physiological Characteristics of Malus hupehensis Seedlings Under Continuous Cropping Evaluation of Peach Rootstock Waterlogging Tolerance Based on the Responses of the Photosynthetic Indexes to Continuous Submergence Stress Preliminary Study on Introducing of Leaf Senescence-Delaying Gene PPF1 into Rice Evaluation of Peach Rootstock Waterlogging Tolerance Based on the Responses of the Photosynthetic Indexes to Continuous Submergence Stress