| Tomato (Lycopersicum esculentum Mill.), belongs to Solanaceae, Lycopersicon,annual vegetable, originates from tropical South America. Its root is strong, extensive, widespread and deep. The lateral root easily regenerates after basal root injured, therefore, tomato has high acclimatization to environment. Tomato nursery area in potting seedlings is the most.Sweet Pepper (Capsicum annuum L.), belongs to Solanaceae, Capsicum, also annual vegetable, originates from Central America and tropical South America. Sweet pepper root is relatively weak, little, and shallow, and mainly allocates 10~15cm deep layer in soil. Under bad nursery and cultural surroundings, root is readily injured. Sweet pepper neither endures drought nor waterlog, not too much water need as well. Since sweet pepper root is not strong enough, consequently strict in water supply. Its nursery area is only less than that of tomato.This experiment used the above two vegetables(tomato and Sweet paper)as material, which are largely different in biological characteristics. We investigated the changes of growth, development, and some physiological, biochemical characteristics under different floor level of water supply in media (RWC is 90%, 75%, 60%, 45%, 30% respectively), and discussed the relation among vigorous index, material accumulation and allocation, nutrition metabolism, carbon and N metabolism, osmotic adjustment and photosynthesis of tomato and sweet pepper seedlings, The main results are as below:1. During transient stress-rewatering, the less water supply, the lower RWC, osmotic potential, saturated osmotic potential, the higher osmotic adjustment and injury degree at the same time. Tomato and sweet pepper had different reaction towards water changes in media. Water content in tomato leaf was relatively lower, so that RWC change was less than sweetpepper towards water deficit, which made tomato keep higher metabolic activity, and reduced injury degree; Enzyme reaction metabolism had some difference between tomato and sweet pepper. The activity of POD,SOD,CAT in tomato increased with decrease of water supply, and of which were more sensitive in sweet pepper. Among the above three protective enzymes, POD and SOD had higher activity than CAT, and SOD was the most sensitive to water deficit; Of all the osmotic solutes, free amino acid and proline were the most sensitive to water change, and their content sharply increased with less water supply, then rapidly reduced after rewatering, basically recovered to the level of CK; Soluble protein might be replaced by free amino acid in tomato to play osmotic role, but it directly worked in sweet pepper. Unlike amino acid, soluble sugar content was basally higher; therefore it possibly made a more important role to osmotic adjustment. After rewatering, osmotic solutes in all treatments reduced to some extent differently.2. Less water supply significantly inhibited growth and development of tomato and sweet pepper seedlings, and changed attribution percentage of dry mass between root and crown. The effect of different status of water supply on function and structure in root and crown could be explained with Function Balance Theory. Namely the less water, the worse function of root and crown, the less net photosynthesis, which led to worse growth and development, and more affected dry matter productivity and function creation. The dry matter of leaf, shoot reduced more than of root. Root and leaf area were the most sensitive indexes to water change, and tomato give priority to basal root, pepper to lateral root. Less water supply reduced all the vigorous indexes based dry matter, but increased endurance indexes (for instance, water architecture features, specific leaf weight et al), and yet in T5 had a little reduction. The anthesis of T3 tomato and T2, T3 sweet pepper was earlier 2~7 days than CK, 14 days than T5. Considering both growth and development, synthesized major constitutes, path analysis, gray systemic theory, we preliminarily screened the vigorous indexes: Tomato: 1.
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