The Effects Of Vine And Fruit Numbers On Plant Growth And Physiological Characters Of Muskmelon

Muskmelon (Cucumis melo var. cantaloupensis L.) is a melon subspecies species of Cucurbitaceae, due to its appearance, fruit with high sugar, nutrient-rich, well accepted by consumers, and it was called as the "fruit Queen".At present, in order to ensure the quality of melon, one fruit per plant cultivation methods are popular in the production. But most varieties of muskmelon maintain vigorous growth after fruit harvest. It would cause great waste if the plant was picked. In high yield cultivation of muskmelon with more fruit per plant, there is a premature senility problem after fruit enlargement. Muskmelon is a vine plant, and the leaves and fruits adhered to their vines are the main "source" and "sink" of muskmelon. Interaction of vines and leaves had greatly influence on the growth and physiological characteristics. By retaining different vine and fruit numbers, a suitable source-sink ratio of muskmelon and the balance between vegetative growth and reproductive growth could be maintained, and the senescence of plant is delayed, the cultivation time is extend, as well as the yield and quality of fruits are improved.To determine the most appropriate number combination of vine and fruit, two muskmelon varieties of'Zhongtian No.1' and 'Zhongtiancuiyu' are employed as the experimental materials in this study. Six different treatment combinations and one control were designed as below:with three levels of vine numbers (one lateral vine, two lateral vines and three lateral vines on the top of main vine) and two levels of fruit numbers (two and three fruits), using no lateral vine and one fruit in conventional cultivation as the control. The effects of vine and fruit numbers on growth, fruit characteristics, physiological characteristics of leaf and root of muskmelon were studied in this paper. Determination of vine and fruit numbers would contribute to delay senescence, as well as providing theoretical basis for high product and efficient cultivation of muskmelon. The main results were as follows.1. Accompany with the extension of growth period, the growth of muskmelon was inhibited significantly by increase of fruit numbers per plant, which was shown that the stem diameter, average internode length and the maximum length of functional leaves increase slowly. However the different treatments of vine numbers had no significant effect on the growth of muskmelon. By increasing fruit numbers, the fruit setting rate of upper fruit (the third fruit located between 12～15 node) decreased significantly, the harvesting time was delayed, the fruit developmental stages were prolonged, the fruit volume,flesh thickness and fruit weight decreased significantly, but the yield per plant, the yield per unit area and the output per unit area all increased significantly. Two fruits and appropriate vine numbers could enhanced fruit quality, while three fruits combined with increasing vine numbers would significantly eliminated the fruit quality, especially the third fruits got the worst quality. Considered the yield, quality and output comprehensively,'Zhongtian No.1' with two vines and two fruits, and 'Zhongtiancuiyu' with three vines and two fruits were the most appropriated combination of vine and fruit numbers.2. The vine and fruit numbers have a significant influence on leaves physiological state and antioxidant characteristics of muskmelon. The approriate numbers of vine and fruit would slow down the decline of total Chl and soluble protein content, reduce the production rate of O2·- and the MDA content, improve the activities of superoxide dismutase(SOD), catalase(CAT) and the As A content, decrease the activity of peroxidase(POD) of the leaf in muskmelon.'Zhongtian No.1' with two vines and two fruits per plant and 'Zhongtiancuiyu' with three vines and two fruits per plant were beneficial to promote the antioxidant ability of leaf and to protect the leaf from senescence.3. The vine and fruit numbers significantly impact on roots vigor and antioxidant characteristics of muskmelon. The appropriate numbers of vine and fruit were also helpful to maintain higher root vigor and to retard the drop of soluble protein content, reduce the production rate of O2·- and the MDA content, enhanced the activities of SOD, CAT and the AsA content, lowered the activity of POD of the root.'Zhongtian No.1' with two vines and two fruits per plant and 'Zhongtiancuiyu' with three vines and two fruits per plant gained the most optimum growth of root.