Salinity represents an increasing environmental problem in managed ecosystems. Populus spp. is widely used for wood production by short-rotation forestry in fertilized plantations and can be grown on saline soil. Because N fertilization plays an important role in salt tolerance, we analysed Grey poplar (Populus tremula ¥ alba, syn. Populus canescens) grown with either 1 mM nitrate or ammonium subjected to moderate 75 mM NaCl. The impact of N nutrition on amelioration of salt tolerance was analysed on different levels of N metabolism such as N uptake, assimilation and N (total N, proteins and amino compounds) accumulation. Na concentration increased in all tissues over time of salt exposure. The N nutrition-dependent effects of salt exposure were more intensive in roots than in leaves. Application of salt reduced root increment as well as stem height increase and, at the same time, increased the concentration of total amino compounds more intensively in roots of ammoniumfed plants. In leaves, salt treatment increased concentrations of total N more intensively in nitrate-fed plants and concentrations of amino compounds independently of N nutrition. The major changes in N metabolism of Grey poplar exposed to moderate salt concentrations were detected in the significant increase of amino acid concentrations. The present results indicate that N metabolism of Grey poplar exposed to salt performed better when the plants were fed with nitrate instead of ammonium as sole N source. Therefore, nitrate fertilization of poplar plantations grown on saline soil should be preferred.
Summary• External salinization can affect different steps of nitrogen (N) metabolism (ion uptake, N assimilation, and amino acid and protein synthesis) depending on the inorganic N source.• Here, we assessed the net uptake of N supplied as nitrate or ammonium and N assimilation (combining metabolite analyses with molecular biological approaches) in grey poplar ( Populus × canescens ) plants grown under saline (75 m M NaCl) and control conditions.• The specific (µmol N g − 1 dry weight fine roots h − 1 ) and total plant (µmol N per plant h − 1 ) N net uptake rates, total plant N content, total plant biomass and total leaf protein concentration were reduced under saline conditions when plants were supplied with ammonium. In both nutritional groups, salt treatment caused pronounced accumulation of soluble N compounds in the leaves. The mRNAs of genes coding for enzymes catalyzing rate-limiting steps of both proline synthesis and degradation (delta-1-pyrroline-5-carboxylate synthase and proline dehydrogenase) as well as for NADH-dependent glutamate synthase were accumulated under saline conditions.• Whereas under control conditions the plant N status seemed to be superior when ammonium was supplied, the N balance of ammonium-fed plants was more severely affected by salt stress than that of plants supplied with nitrate. Possible metabolic implications of stress-related accumulation of particular amino acids are discussed.
The present study shows for the first time the influence of exogenously applied amino acids and cytokinin on the physiological and molecular aspects of N metabolism in poplar trees. In a short-term feeding experiment, glutamine or trans-zeatin riboside ( t ZR) was added directly to the nutrient solution. NO 3 -net uptake declined significantly in response to both treatments. Feeding with glutamine brought about an increase in concentrations of different amino compounds in the roots (glutamine, glutamate, alanine, g -amino butyric acid (GABA) and NH 4 + , which negatively correlated with the net NO 3 -uptake. The plants showed a reduction of cytosolic glutamine synthetase 1 (GS1) transcript level in the roots. In addition, glutamine feeding changed the root-to-shoot distribution on N assimilation in favour of the leaves and plant internal N cycling. t ZR treatment resulted in expansion of zeatin-type (Z-type) cytokinins in the roots and increased nitrate reductase (NR)-mRNA level. The results indicate that both particular amino acids and active cytokinins are involved in the feedback regulation of N uptake and metabolism in poplar. We propose that inhibition of N uptake by cytokinins in poplar is more complex than that mediated by amino compounds, and other effectors are involved in this regulation.
Commercial geese breeding in Poland is based on two strains of White Italian geese (W11 and W33). The crossbreeds W33 (paternal line) and W11 (maternal line) are distributed in Poland under the commercial brand of White Ko³uda® goose. However, there are several breeds which are covered by the animal genetic resources conservation program and kept as conservative flocks. These breeds proved invaluable to commercial geese breeding to stabilize body weight, improve muscling and decrease the amount of fat in the carcass of the crossbreeds. Therefore, this study analyzed the reciprocal crossbreeds of White Ko³uda® geese with the individuals from conservative flocks. DNA polymorphism (RAPD-PCR) of the crossbreeds as well as the phenotypic effect of crossbreeding was evaluated. PCR amplification of five RAPD markers resulted in obtaining 14.25 band/crossbreed group. The genetic similarity of the crossbreeds expressed as band sharing frequency (BS) ranged from 0.44 to 0.97. The direction of crossing of the W33 goose with one of the individuals from the conservative flock strongly affected the genetic similarity estimates. The body weight in the 17 JD or 24 JD week of life and the percentage of leg muscle weight in the 24 JD week of life differed significantly depending on the crossbreed genotype. A similar relationship was demonstrated for egg fertilization and number of nestlings per goose. As the lines were differentiated only by origin of the Z chromosome, the background of the differences in genetic polymorphism and the phenotypic records is hypothesized as (i) the linkage of some production traits with sex chromosomes; (ii) the impact of selection on W33 individuals resulting in lower performance of geese with a W33-derived Z chromosome; (iii) genetic imprinting displayed as the effect of either maternal or paternal origin of the Z chromosome.
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