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本文运用营养液培养方法、~(15)N底物标记及同位素质谱测定技术等,首先鉴定了两烟草(Mcortma品种(‘K326’和‘红花大金元’)吸收NO_3~-及NH_4~+而不发生向地上部转移的最短时间,继而对其吸收的系统组成进行了较精确的测定,发现两品种吸收氮素至转移到地上部仅在数分钟之内;根细胞吸收N至少有两类体系。在N浓度≤1 mmol·L~(-1)时,根系吸收途径具有酶促反应特征;吸收NO_3~-的米氏常数(X_M)值(‘K326’:84.5 mmol·L~(-1);‘红花大金元’:47.8μmol·L~(-1))明显低于对NH_4~+的K_M值(‘K1326’:93.5 mmol·L~(-1);‘红花大金元’:90.4 mmol·L~(-1));‘红花大金元’较低的K_M值可能是该品种较‘K326’耐低N的生理原因之一。外界N浓度>1 mmol·L~(-1)时,根系对N的吸收量与外界N浓度呈正相关;‘K326’对NO_3~-的吸收速率是‘红花大金元’的2倍以上,对NH_4~+的吸收率则为‘红花大金元’的约2.4倍;‘K326’对NO_3~-的吸收速率约为对NH_4~+吸收的3.6倍,而‘红花大金元’对NO_3~-的吸收速率约为对NH_4~+吸收速率的1/2。本研究结果对探索烟草根系吸收氮素的相关分子机理提供了生理学依据。
In this paper, we first identified the absorption of NO_3 ~ - and NH_4 ~ + in two tobacco cultivars (’K326’ and ’Honghua Dajinyuan’) using nutrient solution culture, ~ (15) N substrate labeling and isotope mass spectrometry, + Without the shortest time to transfer to the shoot, and then the absorption of its system to make a more accurate determination and found that two varieties to absorb nitrogen to the shoots transferred to the ground within only a few minutes; root cells to absorb at least N Two kinds of system.When the N concentration was less than or equal to 1 mmol·L -1, the root absorption pathway had the characteristics of enzymatic reaction and the value of X_M absorption (NO 3 - -) of K 3 O 6 (84.5 mmol·L -1) (-1); ’Honghua Daikin’: 47.8μmol·L -1) was significantly lower than that of NH_4 ~ + (’K1326’: 93.5 mmol·L -1) Kudzu gold ’: 90.4 mmol·L -1). The lower K M value of’ Hong Hua Dai Jin Yuan ’might be one of the physiological reasons for the variety’ K326 ’ At 1 mmol·L -1, the uptake of N by the root system was positively correlated with the concentration of N in the external environment. The absorption rate of NO 3 - by K326 was more than twice that of ’Honghua Daikin’ + Absorption rate of ’safflower Daikin’ about 2.4 times; ’K326’ on the absorption of NO_3 ~ - The rate of absorption of NO_3 ~ - was about 1/2 of the absorption rate of NH_4 ~ +. The results of this study are very helpful to explore the mechanism of nitrogen uptake by tobacco roots The relevant molecular mechanism provides a physiological basis.