College of Forestry, Northwest A&F University, Yangling, Shaanxi 712100, PR China.
College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, PR China.
Tree Physiol. 2018 Jan 1;38(1):66-82. doi: 10.1093/treephys/tpx109.
To investigate the physiological responses of poplars to amino acids as sole nitrogen (N) sources, Populus × canescens (Ait.) Smith plants were supplied with one of three nitrogen fertilizers (NH4NO3, phenylalanine (Phe) or the mixture of NH4NO3 and Phe) in sand culture. A larger root system, and decreased leaf size and CO2 assimilation rate was observed in Phe- versus NH4NO3-treated poplars. Consistently, a greater root biomass and a decreased shoot growth were detected in Phe-supplied poplars. Decreased enzymatic activities of nitrate reductase (NR), glutamate synthase (GOGAT) and glutamate dehydrogenase (GDH) and elevated activities of nitrite reductase (NiR), phenylalanine ammonia lyase (PAL), glutamine synthetase (GS) and asparagine synthase (AS) were found in Phe-treated roots. Accordingly, reduced concentrations of NH4+, NO3- and total N, and enhanced N-use efficiencies (NUEs) were detected in Phe-supplied poplars. Moreover, the transcript levels of putative Phe transporters ANT1 and ANT3 were upregulated, and the mRNA levels of NR, glutamine synthetase 2 (GS2), NADH-dependent glutamate synthase (NADH-GOGAT), GDH and asparagine synthetase 2 (ASN2) were downexpressed in Phe-treated roots and/or leaves. The 15N-labeled Phe was mainly allocated in the roots and only a small amount of 15N-Phe was translocated to poplar aerial parts. These results indicate that poplar roots can acquire Phe as an N source to support plant growth and that Phe-induced NUEs in the poplars are probably associated with NH4+ re-utilization after Phe deamination and the carbon bonus simultaneously obtained during Phe uptake.
为了研究杨树对氨基酸作为唯一氮（N）源的生理响应，将美洲黑杨×山杨（Ait.）史密斯植株在沙培中用三种氮肥之一（NH4NO3、苯丙氨酸（Phe）或 NH4NO3 和 Phe 的混合物）进行处理。与用 NH4NO3 处理的杨树相比，用 Phe 处理的杨树具有更大的根系，叶片变小，CO2 同化率降低。一致地，在供应 Phe 的杨树中检测到更大的根生物量和减少的地上部分生长。在 Phe 处理的根中，检测到硝酸还原酶（NR）、谷氨酸合酶（GOGAT）和谷氨酸脱氢酶（GDH）的酶活性降低，而亚硝酸盐还原酶（NiR）、苯丙氨酸解氨酶（PAL）、谷氨酰胺合成酶（GS）和天冬酰胺合成酶（AS）的酶活性升高。因此，在供应 Phe 的杨树中检测到 NH4+、NO3-和总 N 的浓度降低，以及氮利用效率（NUE）提高。此外，假定的 Phe 转运体 ANT1 和 ANT3 的转录水平上调，并且 NR、谷氨酰胺合成酶 2（GS2）、NADH 依赖性谷氨酸合酶（NADH-GOGAT）、GDH 和天冬酰胺合成酶 2（ASN2）的 mRNA 水平在 Phe 处理的根和/或叶中下调。15N 标记的 Phe 主要分配在根部，只有少量的 15N-Phe 被转运到杨树地上部分。这些结果表明，杨树根可以获取 Phe 作为氮源来支持植物生长，并且 Phe 诱导的杨树 NUE 可能与 Phe 脱氨后 NH4+的再利用以及 Phe 吸收过程中同时获得的碳奖励有关。
