The Physiological Mechanism Research Of Nitrate Accumulation Difference In Different Spinach Variety

The massive researchs confirmed that the nitrate was harm for human body .This experiment researched the mechanism of nitrate-N accumulation in different spinach (Spinacia oleracea L.) varieties and analysed the physiological reason. That will be based on the research of reducing nitrate in crops.This experiment planted spinach by pot, field and nourishing cream. In the pot experiment,the nitrate-N contents and NR activity in different spinach varieties were determinated under different nitrogen level, and the nitrate accumulation in different spinach varieties under the influence of nitrogen level and NR activity was analysed. In the field experiment,the the nitrate contents and NR activity in different spinach varieties under different photosynthesis and transpiration were determinated ,and the nitrate accumulation in different spinach varieties under the influence of photosynthesis and transpiration was analysed. In the nourishing cream experiment, root system characteristic and nitric nitrogen absorption dynamics in the different spinach variety were determinated, and the nitrate accumulation in different spinach varieties under the influence of root system absorption was analysed.1. The plant's nitrate-N contents were negative correlated with the rate of root and shoot. The root maybe was the important spot in nitrate-N reduction. Under the different nitrogen level, the biomass of shoot had a few difference, but the nitrate-N contents were very difference. The result indicated that, plant's biomass had not reduced, also the nitric nitrogen content was low under low nitrogen level. Therefore, the employment quantity of fertilizer should be suitable reduced in production. This not only may save the fertilizer resources, also may reduce nitrate-N contents in vegetables to increase food safe.2. Nitrate Reductase ( NR) activity had obviously diversity in different spinach varieties and different organs of the same plant. The in vitro-NR activity were higher than the in vivo-NR activity .Under the low nitrogen level, NR activity were higher in root especially in lateral root. The result showed that, root was an important organ not only for nitrate-N absorption but also for nitrate-N reduction. Under the nitrogen sufficient condition, the nitrate-N contents in spinach were negative adjusted by the NR activity3. Under the same light condition, the nitrate-N contents in different spinach varieties increased with the photosynthesis rate. In other words, the photosynthesis rate certainly promoted the nitrate-N accumulation. It was positive correlation between the nitrate-N contents in Leaf and the potassium content in root.4. The rate of nitrogen absorption was positive correlated with each parameter of root. Thus, the rate of nitrogen absorption possibly increased with each parameter of root.