（Institute of Vegetables and Flowers，Chinese Academy of Agricultural Sciences，Key Laboratory of Biology and Genetic
Improvement of Horticultural Crops，Ministry of Agriculture and RuraL Affairs，Beijing 100081，China）
Abstract：Taking‘Zhongza No.302’as test material，this study divided the growth and development of tomato plug seedlings into 5 stages（stage Ⅰ is from sowing to seedling emergence；stage Ⅱ is from seedling emergence to cotyledon spreading；stage Ⅲ is from cotyledon spreading to seedling with 2 leaves；stage Ⅳ is from seedling with 2 leaves to 3 leaves；and stage Ⅴ is from seedling with 3 leaves to 4 leaves）．Nine nutrient solution concentrations were set in sections．Studies about the effects of nutrient solution concentration block setting on growth and development，nutrient accumulation amount and utilization rate of tomato plug seedlings under ebb-and-flow irrigation system were carried out．The results showed that in stage Ⅰ with irrigation 1.0× nutrient solution concentration，the plug seedling emergence rate was the highest，which was increased by 7.71% than that of the contrast water on the 7th day after sowing．This was obviously higher than those of the other treatments．When the nutrient solution concentration was set as 0.25× in stage Ⅰ，0.25× in stage Ⅱ，1.0× in stage Ⅲ，1.5× in stage Ⅳ and 1.5× in stage Ⅴ（treatment 9），the growth indexes of plug seedling including plant height，stem thickness，leaf area，total root length，root volume，root surface area，root average diameter，dry and fresh weights of stem leaf and root, and strong seedling index，etc.were the best，and the dry weight growth rate of plug seedlings was the highest．The uptake and accumulation of N，P and K were the highest．They were 15.8，10.1，21.0 mg·plant-1，respectively，and the utilization rates were 14.35%，6.10% and 15.92%，respectively．
