Study On Injury Mechanism Induced By NO₃～- Stress To Growth And Development Of Cucumber (Cucumis Sativus L.)

At present, we had lots of achievements on plant salt resistance mechanism, but most of them regarded NaCl as means of researching. The main anion of the soil salinization of the greenhouse was NO₃^-, but interior mechanisms of vegetable damage led by NO₃^- accumulation in greenhouse soil were short of systemic research.On the basis of present study, this subject will probe into the injury mechanism to the cucumber of NO₃^- excessive accumulation in greenhouse soil. We will clarity the distribution of NO₃^- in cucumber organ and the effects of NO₃^- stress on physiological and biochemical indexes, ion transmembrane transportation function protein activity and subcellular Ca2+ distribution in cucumber seedling, in order to establish theory basis to improve rhizosphere condition and lighten alkali-saline injury. The main results obtained were presented as follows:1. The absorption, distribution and utilization of cucumber to nitrogen by 15N tracer technology under NO₃^- stressIn four leaves and six leaves stages, a certain extent, it showed that higher NO₃^- favored growth and development of cucumber plants with increasing of NO₃^- , plant dry matter accumulations and N contents increased. With the growth of cucumber (vine and fruit stages), the large accumulations of N in roots caused the growth inhibition of cucumber plants, even the appearance of wilt. N distribution changed with the growth and development center of cucumber. N utilization efficiency significantly decreased under NO₃^- stress. However, plant N content of N2 (900Kg pure nitrogen per ha.) absorbed from fertilizer was higher than control (450Kg pure nitrogen per ha.), which suggested optimum nitrogen fertilization (450Kg pure nitrogen per ha.) could not satisfy the N need of the plant growth. N partitioning in the cucumber plant organs had significantly differences, and N partitioning in the leaf was highest in all the growth stages.2. Effects of NO₃^- stress on physiological and biochemical index of cucumber seedlings(1) Plant height and area of leaves expanded much more than control under 56 mmol·L-1 NO₃^- concentrations after 7 days of treatment, which showed that it favored growth and development of cucumber plants when nitrate was slightly added based on low-level...