Nitrogen (N) supply, including NO₃^--N and organic N in the form of amino acids can influence the morphological attributes of plants. For example, amino acids contribute to plant nutrition; however, the effects of exogenous amino acids on NO₃^--N uptake and root morphology have received little attention. In this study, we evaluated the effects of exogenous glycine (Gly) on root growth and NO₃^--N uptake in pak choi (Brassica campestris ssp. Chinensis L.). Addition of Gly to NO₃^--N agar medium or hydroponic solution significantly decreased pak choi seedling root length; these effects of Gly on root morphology were not attributed to the proportion of N supply derived from Gly. When pak choi seedlings were exposed to mixtures of Gly and NO₃^--N in hydroponic culture, Gly significantly reduced ¹⁵NO₃^--N uptake but significantly increased the number of root tips per unit root length, root activity and ¹⁵NO₃^--N uptake rate per unit root length. In addition, ¹⁵N-Gly was taken up into the plants. In contrast to absorbed NO₃^--N, which was mostly transported to the shoots, a larger proportion of absorbed Gly was retained in the roots. Exogenous Gly enhanced root 1-aminocyclopropane-1-carboxylic acid synthase (ACS) and oxidase (ACO) activities and ethylene production. The ethylene antagonists aminoethoxyvinylglycine (0.5 μM AVG) and silver nitrate (10 μM AgNO₃) partly reversed Gly-induced inhibition of primary root elongation on agar plates and increased the NO₃^--N uptake rate under hydroponic conditions, indicating exogenous Gly exerts these effects at least partly by enhancing ethylene production in roots. These findings suggest Gly substantially affects root morphology and N uptake and provide new information on the specific responses elicited by organic N sources.

氮(N)供应，包括NO ₃ ^- -N和氨基酸形式的有机氮，可以影响植物的形态属性。例如，氨基酸有助于植物营养；然而，外源氨基酸对NO ₃ ^- -N吸收和根系形态的影响却很少受到关注。在本研究中，我们评估了外源甘氨酸 (Gly) 对小白菜 ( Brassica Campestris ssp. Chinensis L.)根系生长和 NO ₃ ^- -N 吸收的影响。_{在NO 3} ^- -N琼脂培养基或水培液中添加Gly显着降低了小白菜幼苗的根长；甘氨酸对根形态的这些影响并不归因于来自甘氨酸的氮供应比例。水培小白菜幼苗暴露于Gly和NO ₃ ^- -N混合物时，Gly显着降低了¹⁵ NO ₃ ^- -N吸收，但显着增加了单位根长的根尖数量、根活力和¹⁵ NO ₃ ^{- N。} -单位根长度的氮吸收率。此外，¹⁵ N-甘氨酸被植物吸收。与吸收的NO ₃ ^- -N 大部分被输送到芽相反，吸收的Gly 的大部分被保留在根中。外源甘氨酸增强根 1-氨基环丙烷-1-羧酸合酶 (ACS) 和氧化酶 (ACO) 活性以及乙烯产生。乙烯拮抗剂氨基乙氧基乙烯基甘氨酸 (0.5 μM AVG) 和硝酸银 (10 μM AgNO ₃ ) 部分逆转了 Gly 诱导的对琼脂平板上初生根伸长的抑制，并增加了水培条件下 NO ₃ ^- -N 的吸收率，表明外源 Gly 发挥了这些作用至少部分通过提高根部乙烯的产生来产生影响。这些发现表明甘氨酸显着影响根系形态和氮吸收，并提供有关有机氮源引起的特定反应的新信息。