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Nitrogen is the largest and essential nutrients for plants optimal growth and development,and large amounts of nitrogen fertilizers are applied in worldwide to achieve high crop yield.However,excess nitrogen fertilize used leading yield-increasing effect of N fertilize decrease.As a consequence,superfluous nitrogen causes energy loss and a series of environmental problem, and then increased crop cost for farmer in China.Reasonable supply of nitrogen fertilizer is the important measure to realize the high-efficient and high-yield crops, lower N levels of wheat seedling to reduce nitrogen loss, improve the wheat yield and nitrogen use efficiency is of great significance.The hydroponic experiment was conducted to investigate the effects of low nitrogen on growth and nitrogen absorption in two wheat cultivars,Zaoyangmai(low nitrogen sensitive type) and Yangmai158(low nitrogen tolerant type), differing in tolerance to low nitrogen.The results were summarized that low nitrogen supply inhibited the plant growth for both cultivars.It is mainly showed that the plant dry weight reduced including shoot growth decreased,and root growth increased in wheat at low nitrogen treatment.More nutrients were allocated to root to promote the ability of absorption.Chlorophyll content, net photosynthetic rate decreased and stomatal conductance increased for two cultivars during low nitrogen treatment period.Comparison between cultivars showed that chlorophyll content and net photosynthetic rate of were significantly reduced in the top 1st and 2nd leaves of Zaoyangmai, while no significant difference in these factors was observed in Yangmai158 compared with control under N-limited condition;the quantum yield of photosystem Ⅱ (PSⅡ)and the maximum efficiency of PSⅡ photochemistry were only slightly altered in both cultivars, indicating that PSⅡ was not damaged by low N nutrition.The two wheat cultivars root absorption function increased by low-level nitrogen nutrition supply, including root total root length, root surface area and root volumn increased, while average root diameter and free NO3--N concent reduced compared with control for both cultivars under low nitrogen condition.In addition, root maximum absorption rate of nitrate nitrogen(Vmax)and affinity (1/Km) were also showed significant differences by comparing with two wheat seedlings,Yangmai158 was significant higher than Zaoyangmai;Low nitrogen treatment also significantly increased wheat root plasma membrane H+-ATPase hydrolysis activity and proton transport activity, its conforming to enzyme kinetic characteristics of saturated.Yangmai158 root plasma membrane H+-ATPase hydrolysis activity significantly increased and maintain higher level compared with control during nitrogen treatment period, while Zaoyangmai increased at first and then decreased, at finally lower than control.Therefore, the reason of Yangmai158 having higher tolerance to low nitrogen is that it have more stronger plant growth ability and higher biomass, preserve a relatively high nitrogen status so as to maintain normal photosynthesis;it also has a more stronger root group, higher potential nitrogen-uptake rate and higher root plasma membrane H+-ATPase hydrolysis activity and proton transport activity to keep up a higher absorption capacity.