Effects of exogenous substances on active oxygen metabolism and photosynthesis in tomato seedlings under drought stress

In this paper,the authors investigated the effects of different exogenous substances,10 mmol/L CaCl2,5 mmol/L GABA,0.5 mmol/L Put,0.5 mmol/L Spd,on active oxygen metabolism and photosynthesis in tomato seedlings 'Jin Peng No.1' under drought stress.The results showed that,compared with CK,when tomato seedlings were grown under drought stress,plant growth,photosynthesis system Ⅱ(PSⅡ) and soluble protein content were restricted or reduced,and the contents of free amino acids and soluble sugar were increased.Meanwhile,the variation of active oxygen metabolism leaded to MDA accumulation.Seedlings grown with exogenous substances of CaCl2,GABA,Put,and Spd under drought stress improved plant growth in height,stem diameter and root,and increased fresh weight,dry weight together with the contents of soluble protein,free amino acids and soluble sugar.The exogenous substances reduced the O·-2 production rate,decreased the contents of H2O2 and MDA by increasing the activity of SOD,POD and CAT,and kept Fv/Fm,ΦPSⅡ,qP,ETR at high levels,so as to relieve the seedling damage under drought stress.The average subordinate function analysis showed that different exogenous substances reacted drought stress in different ways: Put relieved the damage of drought stress mainly through improving plant growth,and GABA mainly through weakenning the harm to photosystem Ⅱ and active oxygen metabolism in leaves,however,Ca2+ mainly through increasing the contents of osmoregulation substances.