| Cucumber (Cucumis sativus L.) is an important vegetable worldwide, also a widely cultivated vegetable crop in protection field. At present, seedlings transplanting was mainly used in cultivation. The seedlings might easily be spindling when environment was incorrectly controlled in the process of nursery, which lead to the decline of the seedlings quality, and then affecting the growth, flower bud differentiation, fruit setting and fruit development of cucumber, finally influence the products yield as well as quality.Two different ecotypes of cucumber cultivars ’Deltastar’ and ’No.4 Jinchun’ were used as the test materials to study the effects of seedlings leggy extent on cucumber plant growth, fruit yield and quality; to study the effects of supplementary ultraviolet-B(UV-B) radiation on the growth and physiological characteristics of leggy cucumber seedlings, and illumination supplement with light-emitting diode sources on regulating cucumber seedlings spindling, exploring the possibility of supplying illumination on the management of the excessive growth; to investigate the simulation model of cucumber seedlings healthy index based on radiation and thermal effectiveness, by analysising the quantitative relationship between healthy index and two main ecological factors, temperature and light, providing an optimized management of temperature and light on controlling spindling and strengthening seedlings. Through a systematic study on regulation cucumber seedling spindling by supplemental lighting and cucumber healthy index simulation model, providing theoretical and technological basis for seedlings leggy regulation. The major results were as follows:1. Effects of seedlings leggy extent on cucumber plant growth, fruit yield and quality were studied. The results showed that different degrees of leggy growth of cucumber seedlings occurred under shading conditions, and have a significant impact on the plants growth, fruit yield and quality after planting. The plant height and hypocotyl length of leggy seedlings were significantly higher than the control, but stem diameter, leaf area, dry weight, the content of dry matter, root/shoot ratio and seedling index all displayed opposite changing trend. After planting, the plant morphology was significantly differed from those of control seedlings. Compared with the control, in leggy seedlings, the early blooming period delayed; the node of the 1st female flower was higher; while the average pod number per plant, fruit weight, and early yield per plant and per unit area were all significantly decreased; fruit soluble solids, the content of soluble sugar, soluble protein and Vc were also significantly reduced as well. It suggested that the leggy seedlings of cucumber after planting had significant negative effects on plant growth and fruit yield and quality.2. Effects of supplementary ultraviolet-B (UV-B) radiation on the growth and physiological characteristics of leggy cucumber seedlings. The results showed that under simple low light, the plant height, MDA content and electrolyte leakage increased, while stem diameter, seedling dry weight, root-shoot ratio and root activity, photosynthetic pigment and soluble protein content decreased; cucumber seedlings presented serious spindling. Supplementary UV-B radiation under low light could inhibit plant height significantly. Low intensity UV-B radiation could control overgrowth effectively without harm, while high intensity would affect the normal physiological activity of plants, and result in stress damage, and the effects also related to the hours of UV-B irradiating. In sum, compared to the simple low light treatment(TO),0.15w·m-2(T1) UV-B radiation for 14d could significantly reduce plant height, increase stem diameter, dry weight, root-shoot ratio and healthy index, contribute to the formation of chlorophyll, enhanced root activity, leaf soluble protein and pro content, decline leaf MDA content and electrolyte leakage, promoted the PAL activity, UV absorbing compounds and flavonoid content, which suggested that the appropriate intensity UV-B radiation could effectively control spindling and cultivate healthy seedlings.3. The effects of supplement with red and blue light-emitting diode sources on the growth and physiological characteristics of cucumber seedlings were studied. The results showed that the cucumber seedlings under simple low light were significantly differed from those of the control seedlings. The plant height was significantly higher than that of the control, while stem diameter, dry weight, healthy indexs were significantly lower. Moreover, the chlorophyll content, soluble protein content and root activity were significantly reduced, MDA content and membrane permeability increased, causing a serious spindling. Supplement with red and blue light-emitting diode sources could inhibit excessive growth significantly, and 90μmol·m-2·s-1 and 180μmol·m-2·s-1 intensity red and blue light-emitting diode sources could significantly reduce plant height, increase stem diameter, dry weight, root-shoot ratio and healthy index, enhance the root activity, chlorophyll and soluble protein content, but decline MDA content and electrolyte leakage. 180μmol·m-2·s-1 intensity has the best effect. It indicated that supplement with red and blue light-emitting diode sources with appropriate intensity could effectively control overgrowth of cucumber seedlings.4. The aim of this study is to investigate the relationship between both temperature and photosynthetically active radiation (PAR) and the healthy indicators(root-shoot ratio, G value, healthy index) of greenhouse cucumber, providing an optimized management of environment on controlling spindling and strengthening seedlings. The simulation model of cucumber seedlings healthy index based on thermal effectiveness and PAR (TEP) was built, through different sowing date test and regression analysis. The model was detected by different warities and sowing date. The results illustrated that root-shoot ratio was poor fitting with TEP, and G value simulation model was low compliance between simulated and observed values, inaptitudeing to simulate through photothermal product as a variable. The detection of healthy index simulation model for greenhouse cucumber seedlings suggested that the model has better predictive accuracy, which could be used to analyze the relationship between healthy index and environmental temperature and radiation, and could be used in management of nursery. |
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