Study On Improving Fruit Qualities Of Tomato By Deicit Irrigation

In order to improve tomato fruit quality, the effect of different level and period of deficit irrigation on plant physiology, fruit quantity and quality were studied by control irrigation amount. On the basis of analyzing water productivity, the management model of deficit irrigation was suggested. Plant growth, photosynthetic and physiological characteristics, fruit quality, yield were studied under simulated drought stress by use of CaCl₂ solution. The mechanism of improving tomato quantity by deficit irrigation was also discussed. It was found that plant has adapting phenomena in drought stress, which means that plant has adapting ability to suit drought.l)Under deficit irrigation, water potential and transpiration rate decreased, free water decreased and bound water increased, photosynthetic rate, stomatal conductance and intercellular CO₂ reduced. 2) Deficit irrigation treatment can improve fruit quality, SSC, organic acid, vitamin C and sugar/acid ratio increased, but the yields decreased. Fruit amount didn't change while per fruit weight reduced. Deficit irrigation can increase water productivity. 3) The management model of deficit irrigation was suggested as that the beginning period of deficit irrigation is swelling period of first cluster, and suitable deficit level is 50⁷5% of normal irrigation management. 4) Simulated drought stress affect also plant physiological characteristics, water potential and transpireation rate decreased, free water decreased and bound water increased, photosynthetic rate reduced. Effect of simulated drought stress on yields and quality is similar to drought stress. 5) Sucrose invertase is important to fruit quality. AI and NI activity intensified in deficit irrigation, which resulted that the contents of glucose and fructose increased. Proline, glucose and fructose content increased in drought stress as important osmotic adjust substance. The mechanism of improving quality of deficit irrigation is that fruit can adjust itself, not shrink water. 6) It was found that plant has adapting phenomena in drought stress, which means that plant has adapting ability to suit drought. Plant changes physical and chemical characteristics to adapt stress, and adjust itself automatically. ABA, soluble sugar and proline play an important roles in adapting phenomena.