| Tomato (Lycopersicon esculentum Mill) is the most important large-scale cultivation of vegetables in horticulture in northern China. Usually, the light intensity in facility can't fill the need of tomato growth, which leads to the decline of yield and quality. Nitrogen condition, which is one of the three main nutrient factors of vegetables, directly decides the yield and quality. As two most important crop's growth factors, light and nitrogen interactively affect the production and distribution of material, and carbon and nitrogen metabolism. The coordination of carbon and nitrogen metabolism not only affects the growth and development of crop but also relates to the yield and quality of crop. So it is vital for high yield and good quality of crop to reasonably control carbon and nitrogen nutrition.With potted Dongnong 708 as experiment material, four levels of light intensity (100%, 70%, 50% and 30% natural light intensity) and four levels of nitrogen supply (0 kg/667m2, 8 kg/667m2, 16 kg/667m2 and 24 kg/667m2) were setted as experimental factors, effects of light and nitrogen on tomato growth condition, dry matter distribution, nutrition uptake, soil physico-chemical properties, photosynthesis, and carbon and nitrogen metabolism were studied. The general rule of carbon and nitrogen metabolism in tomato development was explored in order to increase tomato quality, harmonize yield and quality, make sure of the reasonable nitrogen supply in different light intensity, and provide theory basis for tomato sustainable high effect cultivation. The main conclusions of this study are as follows:1. The interaction of light intensity and nitrogen has significant effect on growth status of tomato. Tomato leaf area, fruit setting rate, dry matter accumulation and dry matter distribution to fruit were promoted by nitrogen in the same light intensity. Shading treatments promoted tomato plant height and leaf area, and decreased stem diameter in the same nitrogen level. 70% natural light intensity treatment increased fruit setting rate, dry matter accumulation and dry matter distribution to fruit while less than 70% natural light intensity treatments had opposite effects.2. The interaction of light intensity and nitrogen has significant effects on root activity of tomato, nutrient absorption and physical and chemical properties of soil. Nitrogen had favorable effects on tomato root activity, total nitrogen and potassium contents of leaf and fruit in the same light intensity, while total potassium contents of leaf and fruit in 24 kg/667m2 nitrogen treatments were less than these in 0 kg/667m2 treatments. Nitrogen was unfavorable for the increase of total phosphorus contents of leaf and fruit. Nitrogen increased soil alkali-hydrolysable nitrogen content and soil conductivity, but decreased soil available potassium content in the same light level. Under 70% and 100% natural light intensity, soil available phosphorus contents were the highest in 8 kg/667m2 nitrogen treatments, then declined with the increase of nitrogen supply. Nitrogen promoted soil available phosphorus content under less than 70% natural light intensity.Shading treatment promoted total nitrogen, phosphorus and potassium in leaf and fruit in the same nitrogen condition. 70% natural light intensity treatment promoted root activity, while inhibited soil conductivity, soil alkali-hydrolysable nitrogen, soil available potassium and soil available phosphorus contents. The trends were opposite in less than 70% natural light intensity treatments.3. The interaction of light intensity and nitrogen has significant effect on photosynthesis of tomoto. In 70%-16 treatment, tomoto net photosynthetic rate, stomatal conductance and transpiration rate was the highest, while cell CO2 concentration was the lowest. Both nitrogen and shading treatments increased tomato leaf Chla and Chlb contents, but decreased Chla/Chlb.4. Accumulations of sugar contents in tomato leaf were mainly controlled by SPS and SS activities in early plant growing stage, AI and NI activities also affected that in later growing stage. Accumulations of sugar contents in tomato fruit were mainly controlled by SS, AI and NI activities, but merely by SPS activity.70% natural light intensity treatment increased fruit SS activity and leaf SPS activity, also promoted accumulation of fruit starch in early fruit development stage in the nitrogen level. Nitrogen had the same effects in the same light level. So leaf supply capability of sucrose increased and made it favorable to import photosynthates into fruit. In later fruit development stage, fruit AI activity was the hightest in 8 kg/667m2 nitrogen treatment under 70% and 100% natural light intensity, and in 0 nitrogen treatment under less than 70% natural light intensity. And it was the highest in 70% natural light intensity in the same nitrogen. Increased fruit AI activity decomposed starch and sucrose, accumulated in early development stage, into glucose and fructose, which enhanced fruit quality.5. In the same light condition, nitrogen increased NR and GS activities, which promoted nitrogen assimilation. In the same nitrogen level, less than 70% natural light intensity treatments inhibited NR and GS activities, while 70% natural light intensity treatment had the opposite effects.6. Taken yield and tomato quality into account, 8 kg/667m2 was the appropriate nitrogen supply in 70% and 100% natural light intensity, 0 kg/667m2 in less than 70% natural light intensity. |
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