《植物生理学报》 2017, 53(4): 572-580

¹⁵N短时标记法鉴定烟草‘K326’和‘红花大金元’吸收NO₃^–和NH₄⁺的生理动力学特征

何明洁^1,3, 范腾飞³, 杨超², 陈益银², 李迪秦¹, 李常军^2,*, 刘来华^1,3,*

¹湖南农业大学农学院, 长沙410128; ²重庆烟草科学研究所, 重庆400715; ³中国农业大学资源与环境学院, 植物-土壤相互作用教育部重点实验室, 北京100193

通信作者：李常军；E-mail: hnbjpxy@163.com; LL1025@cau.edu.cn

摘　要：

本文运用营养液培养方法、¹⁵N底物标记及同位素质谱测定技术等, 首先鉴定了两烟草(Nicotiana tabacum)品种(‘K326’和‘红花大金元’)吸收NO₃⁻及NH₄⁺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NO₃⁻的米氏常数(K_M)值(‘K326’: 84.5 μmol·L^-1; ‘红花大金元’: 47.8 μmol·L^-1)明显低于对NH₄⁺的K_M值(‘K326’: 93.5 μmol·L^-1; ‘红花大金元’: 90.4 μmol·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NO₃⁻的吸收速率是‘红花大金元’的2倍以上, 对NH₄⁺的吸收率则为‘红花大金元’的约2.4倍; ‘K326’对NO₃⁻的吸收速率约为对NH₄⁺吸收的3.6倍, 而‘红花大金元’对NO₃⁻的吸收速率约为对NH₄⁺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。

关键词：烟草; ‘K326’; ‘红花大金元’; ¹⁵N标记; 吸收动力学

收稿：2016-12-20   修定：2017-03-11

资助：中国烟草总公司重庆市公司科技计划基金(NY2014040-1070017)。

Physiological characterization of NO₃⁻ and NH₄⁺ uptake kinetics of tobacco ‘K326’ and ‘Honghuadajinyuan’ using a short-time ¹⁵N-substrate labeling approach

HE Ming-Jie^1,3, FAN Teng-Fei³, YANG Chao², CHEN Yi-Yin², LI Di-Qin¹, LI Chang-Jun^2,*, LIU Lai-Hua^1,3,*

¹College of Agronomy, Hunan Agricultural University, Changsha 410128, China; ²Chongqing Tobacco Science Research Institute, Chongqing 400715, China; ³Key Laboratory of Plant-Soil Interactions, Ministry of Education / College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China

Corresponding author: LI Chang-Jun; E-mail: hnbjpxy@163.com; LL1025@cau.edu.cn

Abstract:

In this article, by using a nutrient-hydroponic culture method, ¹⁵N-substrate labeling and mass spectrum-based element measurement techniques, we identified firstly a minimum time when N was not transported to upper parts of two tobacco (Nicotiana tabacum) varieties after their root uptake of NH₄⁺ and NO₃⁻, and subsequently characterized processes and components of N absorption by roots. Our data show that the time for the movement of N from its uptake by the roots to the upper parts of the two varieties happened within only several minutes, and that at least two different systems for the N uptake should exist in the tobacco roots. When external N concentrations were ≤1 mmol·L^-1, the process of the root N-uptake displayed an enzymatic action property; K_M values [i.e. ‘K326’: 84.5 μmol·L^-1; ‘Honghuadajinyuan’ (‘HD’): 47.8 μmol·L^-1] for NO₃⁻ absorbed by the roots were significantly lower than that for NH4+ (‘K326’: 93.5 μmol·L^-1; ‘HD’: 90.4 μmol·L^-1), suggesting that the lower K_M for NH₄⁺ or NO₃⁻ uptake by ‘HD’ would be one of critical physiological factors for a better tolerance of ‘HD’ to low N than that of ‘K326’. As external N>1 mmol·L^-1, N acquisition by the roots was positively proportional to external N concentrations; the rate of NO₃⁻ uptake by ‘K326’ was more than 2-fold higher than that of by ‘HD’, and the rate of NH₄⁺ uptake by ‘K326’ was 2.4-fold lower than that of by ‘HD’; the uptake rate of ‘K326’ for NO₃⁻ was 3.6-fold higher than for NH₄⁺, and ‘HD’ for NO₃⁻ was half as many as for NH₄⁺. Our results may provide physiological evidence for further exploration of molecular mechanisms of N uptake by the roots of tobacco plants.

Key words: tobacco; ‘K326’; ‘Honghuadajinyuan’; ¹⁵N-labeling; absorption kinetics