The effect of nitrogen source and levels on hybrid aspen tree physiology and wood formation

• Published in: Physiologia plantarum Vol. 176; no. 1; pp. e14219 - n/a
• Main Authors: Renström, Anna, Choudhary, Shruti, Gandla, Madhavi Latha, Jönsson, Leif J., Hedenström, Mattias, Jämtgård, Sandra, Tuominen, Hannele
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.01.2024; Wiley Subscription Services, Inc
• Subjects: Accumulation; Amino acids; Ammonium; Ammonium Compounds - metabolism; Availability; Biomass; Decision making; Density; Fibers; Forest Science; Gene sequencing; H-type lignin; Hardwoods; Lignin; Lignin - metabolism; lignin composition; N-nutrition; Nitrates; Nitrates - metabolism; Nitrates - pharmacology; Nitrogen; Nitrogen - metabolism; Nitrogen sources; organic vs. inorganic N; Populus - metabolism; Populus tremula x P. tremuloides; Pyrolysis-GC/MS; Skogsvetenskap; Trees; Trees - physiology; Trävetenskap; Wood; Wood - metabolism; Wood Science; Xylem; xylogenesis; xylogenesis; Populus tremula x P. tremuloides; lignin composition; H-type lignin; N-nutrition; Pyrolysis-GC/MS; organic vs. inorganic N
• ISSN: 0031-9317; 1399-3054; 1399-3054
• DOI: 10.1111/ppl.14219

Nitrogen can be taken up by trees in the form of nitrate, ammonium and amino acids, but the influence of the different forms on tree growth and development is poorly understood in angiosperm species like Populus. We studied the effects of both organic and inorganic forms of nitrogen on growth and wood formation of hybrid aspen trees in experimental conditions that allowed growth under four distinct steady‐state nitrogen levels. Increased nitrogen availability had a positive influence on biomass accumulation and the radial dimensions of both xylem vessels and fibers, and a negative influence on wood density. An optimal level of nitrogen availability was identified where increases in biomass accumulation outweighed decreases in wood density. None of these responses depended on the source of nitrogen except for shoot biomass accumulation, which was stimulated more by treatments complemented with nitrate than by ammonium alone or the organic source arginine. The most striking difference between the nitrogen sources was the effect on lignin composition, whereby the abundance of H‐type lignin increased only in the presence of nitrate. The differential effect of nitrate is possibly related to the well‐known role of nitrate as a signaling compound. RNA‐sequencing revealed that while the lignin‐biosynthetic genes did not significantly (FDR <0.01) respond to added NO3−, the expression of several laccases, catalysing lignin polymerization, was dependent on N‐availability. These results reveal a unique role of nitrate in wood formation and contribute to the knowledge basis for decision‐making in utilizing hybrid aspen as a bioresource.