Effects Of Leaf Nitrogen Content On Leaf Photosynthesis Of Manchurian Ash Seedlings

Nitrogen is one of the most important elements that are vital to plant growth. Also, it is the most familiar restriction factor to plant individual, even natural ecosystem and manual ecosystem (Agricultural system is also included). Nitrogen is; not only the most important structural substance in plant, but the primary composition of enzymes, which are the most active substances in physiological metabolism and exist everywhere.The deficiency of nitrogen, phosphorus and kalium in plant must reduce the leaf photosynthetic rate and non-stomatic factors induce this. The photosynthetic rate of leaves at different nitrogen nutritional status is remarkably relative to ribulose-1, 5-bisphosphate-carboxylase (Rubisco) activity. Thus, studies on the mechanisms of effects on leaf photosynthetic rate by leaf nitrogen content are of significance to direct cultivating seedlings and to improve seedlings' bio-mass accumulation.In this present dissertation, experiments were earned out in greenhouse, and one-year-old and sowing Machurian Ash (Fraxinus mandshurica) seedlings were potted in sand. All of the necessary nutrient elements rooted in nutrient solution. During the seedlings cultivating, sampled termly and determined some physiological indexes, then analyzed and studied the relations among seedling leaf nitrogen content, chlorophyll content, soluble protein content, Rubisco activity, photosynthetic rate and so on. And the results suggested:Machurian Ash seedling leaf nitrogen content is linearly relative to the nitrogen supply levels. And the leaf photosynthetic rate is regulated by Rubisco activity greatly. Leaf nitrogen content induces remarkable effect on chlorophyll and soluble protein content. In plant leaf, more than 50% of soluble protein is Rubisco, and the proportion that leaf total nitrogen mass allocates to soluble protein can accordingly increase when leaf nitrogen content increases, thus total Rubisco protein content and activated Rubisco protein content will all improve and Rubisco relativeactivity also increases. The result of these varieties is to accelerate photosynthesis and improve seedlings' bio-mass accumulation.There exists some remarkable plus correlative relation between Machurian Ash seedling leaf net photosynthetic rate under light saturated condition and leaf nitrogen content. Supply more nitrogen nutrition to seedlings properly can induce leaf nitrogen content accordingly and accelerate leaf photosynthesis, be propitious to bio-mass accumulation.In general, one of the important biological factors, which influence leaf photosynthesis of Manchurian Ash seedlings, is Rubisco activity. So, when Manchurian Ash seedlings are cultivated, in order to increase seedlings leaf nitrogen content and leaf Rubisco activity, accelerate leaf photosynthesis and bio-mass accumulation, we should reasonably fertilize.