| Flower bud differentiation is the basis of flowering. Rhododendron hybrides at different blossoming stages was chosen as the material. In order to explore the potential physiological mechanisms of flower bud differentiation of Rhododendron hybrides to provide theoretical references for improving flowers' quality and regulationing florescence of Rhododendron hybrides in production, the morphological characteristics and the physiological and biochemical changes in the process of flower bud differentiation were studied in the dissertation. The main results were as follows:1.The process of flower bud differentiation of Rhododendron hybrides included five phases: initial differentiation stage, sepal differentiation stage, petal differentiation stage, stamen differentiation stage and pistil differentiation stage.2.Flower bud differentiation at the middle of June is the demarcation point of change of height. Change of height of 3 varieties increased rapidly before the middle of June, after that time change of height tended to be stable. Numbers of spreading leaves and the angles of divergence released the same regularity.3.Change of dry matter content of 3 varieties tended to be stable during flower differentiation perod. With the beginning of reproductive growth, dry matter transfered constantly to reproductive organs, thus content of dry matter gradually decreased.4.With the process of the flower formation, the content of soluble sugar, starch and protein increased at the very beginning, then declined, and partially returned in the end. During the transfer from vegetation growth to reproduction growth of Rhododendron hybrides, the content of soluble sugar, starch and protein were in an increasing state, reaching to the peaks in the flower bud physiological differentiation period. During flower bud morphological differentiation, the content of soluble sugar, starch and protein decreased sharply, and then partially returned until the end of flower bud differentiation.5.The change law of contents of chlorophyll of 3 varieties was basically identical during flower differentiation perod. Contents of chlorophyll all increased before flower bud differentiation, then stasised slightly during flower bud initiation, and kept stable thereupon. 6.The activities of POD, PPO and PAL in leaves showed a double-peak curve.7.The content of soluble sugar, starch and protein in leaves of those plants whose flower bud hadn't formed were all at a relatively low level during flower differentiation perod. In the stage of flower bud differentiation, the activities of POD, PPO and PAL increased at first and then declined. But they were all at a relatively low level. From the above, we can draw a conclusion that a large number of solubility sugar, starch and protein, relatively high reactive level of POD, PPO and PAL might be favorable to the flower bud formation of Rhododendron hybrides.8.The contents of soluble sugar and chlorophyll increased before flower bud differentiation, indicating these indexes are favorable to flower bud initiation of Rhododendron hybrides. According to the observations of the paraffin section, it is found that the critical point of flower bud differentiation of the early-blooming type is between June 1st and June 15th; the mid-blooming type is between June 15th and June 30th; and the late-blooming type is between June 30th and July 15th. In order to ensure the flower quality and quantity of Rhododendron hybrides, according to variety characteristics we should take cultivation and management measures timely, in order to meet the demands of nutrient metabolism: enough water and a complete fertilizer with N-fertilizers being dominant are need for promoting nutritious substances accumulation before flower bud differentiation; when flower bud initiation of Rhododendron hybrides will soon be started, we should control water properly and apply fertilizer with phosphorus potassium being dominant, to ensure the transformation from vegetative growth to reproductive growth timely. |
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