Phenylalanine as a nitrogen source induces root growth and nitrogen-use efficiency in Populus × canescens

Abstract

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.

Changes in Bitter Fennel Essential Oils Exposed to Foliar Spray with L-Phenylalanine

“…A savory plant treated with L-Phe produces higher values of herbs, EO yields, and EO constituents (carvacrol, p-cymen, α-pinene, and γ-terpinene) than those treated with distilled water (Poorghadir et al, 2020). L-Phe is a source of N (Jiao et al, 2017). N is one of the elements essential for plant growth and development because it affects many enzymes that control plant physiological processes, such as EO formation and production; it is also found in all plant cells, plant proteins, hormones, and chlorophyll (Khalid, 2012).…”

“…L-Phe is a precursor of different antioxidant substances, such as salicylate, flavonoids, anthocyanins, and tannins that protect plants from various stress conditions (Pascual et al, 2016). Studies have demonstrated that L-Phe is a nitrogen source, which plays an essential physiological role in plant growth and development (Jiao et al, 2017). Previous studies indicated that L-Phe improves the contents of EO and its constituents in hyssop, savory, and Khella plants (Talaat et al, 2014;Aghaei et al, 2019;Poorghadir, 2020).…”

Genome-wide identification of BXL genes in Populus trichocarpa and their expression under different nitrogen treatments

“…Seedlings treated with 1 mM NH 4 NO 3 served as the control. Roots, stems, leaves, and apical buds of the plants with uniform growth were selected, and the stems and leaves were divided into upper parts (formed during the different nitrogen treatments) and lower parts (formed before the nitrogen treatments) (Jiao et al 2017). The collected samples were immediately frozen in liquid nitrogen kept at − 80 °C until analysis.…”

Morphological, physiological, and transcriptional responses to low nitrogen stress in Populus deltoides Marsh. clones with contrasting nitrogen use efficiency

“…Plants usually acquire N from the soil in the form of NO 3 − and NH 4 + by the roots, with the help of specific transporters, including nitrate transporters (NRTs) and ammonium transporters (AMTs) [ 12 ]. Poplar roots could acquire phenylalanine as a sole N source to support plant growth [ 13 ]. In contrast to herbaceous plants, N nutrition of poplar is maintained by seasonal and internal N circulation, and the vegetative storage proteins (BSP, WIN4, and PNI288) play a role in N storage and seasonal N cycling in poplar [ 14 ].…”