Effects Of Root Zone Volume And Regulated Deficit Irrigation On Physiological Characteristics And Fruit Quality Of Melon

The melon (Cucumis melo L.) occupies an important position in the horticultural industry in the world, and its planting area and total yield in our country all come first in the world. With the improving in living standard of people, the quality of melon fruit were taken into account more and more. Two cultivars of melon (cv.'Elizabeth 239'and 'Qingwang') were used in the present experiment. The effects of root zone volume and regulated deficit irrigation on physiological characteristics and quality of melon fruit were investigated, and the optimum method of root zone volume and regulated deficit irrigation in improving in the yield and quality of melon fruit were selected. The main contents and results in the present study are as follows:1. A melon cultivar cv.'Elizabeth 239'was used. The effects of different container volume [Volume:14 L,8 L,5 L; Ground substance dosage:13 L,7 L,4 L] on the physiological characteristics and fruit quality of melon were investigated. The results showed that plant height, stem diameter, as well as the photosynthetic rate, leaf relative water content and relative chlorophyll content of melon plants were all decreased gradually, with the decrease in the volume of container. Compared to the cultivation treatment with 14 L container, the female flowering and fruit ripening of melon plants under cultivation treatment with 5 L container delayed for 3 and 5 days, respectively, whereas no significant changes were detected under cultivation treatment with 8 L container. In addition, the titratable acidity content in melon fruit decreased under cultivation treatment with 8 L container, and the ratio of soluble solids to total acid, fructose and glucose content increased significantly. This result implied that the taste of melon fruit was improved by cultivation treatment with 8 L container.8 L container could be the optimum volume in improving the fruit quality of melon by root zone volume.2. A melon cultivar cv.'Qingwang'was used. Five treatments were conducted, including the sufficient water supply during the whole growth period as control (T1), Low water deficits (LD) and moderated water deficits (MD) at the vine-extending stage [T2 (LD), T3 (MD)] and fruit expanding stage [T4 (LD), T5 (MD)]. The effects of regulated deficit irrigation on the physiological characteristics, yield, and fruit quality of melon were investigated. The results showed that under T4 (LD) treatment, the transpiration rate and stomatal conductance in melon leaves, the fruit firmness and ratio of the soluble solids to total acid in melon fruit, and the water use efficiency of melon plants increased by 8.44%,75.07%,10.39%,7.22%, and 7.57%, respectively, the amount of irrigation water saved by 5.86%, and no significant effects on the photosynthetic rate and yield of melon fruit were detected. The fruit yield and water use efficiency of melon decreased significantly under other treatments. The content of characteristic aroma components increased significantly under T4 (LD) treatment, and the total amounts of aroma constituent showed highest. These results indicated that the treatment of low water deficit treatments during the fruit maturation stage [T4 (LD)] was a valid strategy to improve the quality of melon fruit.