Abstract: It was investigated that the effects of low temperature on germination of tomato seed at the different days after sowing in climatic chamber.The 3 grades of low temperature were 7～12℃,5～10 ℃,and 3～8℃ respectively,with the CK was 18～25℃(min-max temperature during 24 hrs).The results showed that the tomato seed germination process began affected as the daily average temperature was less than 10.0℃(corresponding to 7～12℃ treatment),the temperature was lower,the impact on germination was greater compared with CK.Furthermore,the earlier low temperature encountered,the impact on germination of tomato seed was greater.As low temperature was encountered within three days after sowing,germination potentials,germinating index,germination rate of tomato seed were all sharp descend.But effects of low temperature on three indexes decreased significantly when it affected six days after sowing.Low temperature effects on tomato seed germination resulted in the descend of α-amylase activities,and the ascend of relative ion leakage of tomato seed,and thus decreased the degradation of tomato seed starch and enhanced the permeability of seed cell membrane.To be sure enough and strong seedlings,it should be avoid seeding tomato during first 7 days after sowing culture in open.

Key words: Tomato seed, Tomato seed, Low temperature stress, Germination, α-amylase activities, Relative ion leakage