Effect of the Water Dry Stress on the Young Plant Morphology and Protective Enzyme Activity of Greenhouse Tomato

‘Jinfen 2'tomato was used as test material,designed 4soil moisture gradients test,from April 25 thto May 30 th,2014,and the treatments of mild,moderate,and severe water stress were T1,T2,and T3,with normal irrigation as CK,to study soil moisture stress on tomato seedling morphological index and protective enzymes.The results showed that with stress time increased,SOD,POD,CAT activity and MDA content had different degrees of increasing.Moreover in the same period SOD,POD,CAT activity presented trend of CKT1T2T3,while MDA content was expressed as T3T2T1CK,besides there were significant differences between different treatments.Tomato was affected less under mild stress,but the long-term moderate and severe stress would destroy cellular structure more seriously;Under water stress,the plant height,diameter coarse,leaf number and leaf area index of late seedling stage tomato all reduced to some extent,and that under the severe stress decreased more especially,only reaching 61.0%,56.3%,60.1% and 48.3% of CK respectively;mild water stress could significantly promote root growth,and the amplifications of total surface area and root tip of T1 were as much as 34.5% and 38.5% compared with CK.And T2 roots advantages compared to CK gradually weakened over time,while the final total root length,total surface area,average diameter and the number of root tips of T3 were only 30.2% 34.5%,61.5% and 32.7% of CK respectively.Studies showed that water stress could inhibit the growth of tomato above-ground part,but mild stress could significantly promote the growth of root system.Short-term moderate stress was beneficial to root growth,but with the extension of stress time,the promotion would gradually diminish or even into inhibition.And under severe stress,tomato root was obvious inhibition.The study provided the scientific basis for water management of greenhouse tomato.