Characteristics of Carbon and Nitrogen Metabolism in Barley Genotypes under Different Nitrogen Supply and Drought Conditions

The interaction between carbon and nitrogen assimilation and their efficiency are key importance for plant production. Applying optimal nitrogen amount at total genetic potential, more carbon assimilation per unit nitrogen would increase biomass. The supply of nitrogen is crucial for leaf growth and the role of nitrogen in agricultural production is intimately connected with photosynthesis. Photosynthetic rate correlates closely with leaf nitrogen content in several plants. At the same time low photosynthetic potential per gram of leaf does not directly cause the slow growth of nitrogen deficient plants. Previous studies focused on investigating mainly the intensity and products of dark reaction of the photosynthetic pathway. Less result have about light reaction affected by genotypic and nitrogen supply variations, mainly under stress conditions. The main goal of this research was to investigate some physiological parameters of barley genotypes under two nitrogen contents and water deprivation conditions at anthesis. Dry weight of plants was determined with thermo-gravimetric method. Relative chlorophyll content measurement was applied to follow the total chlorophyll contents of leaves. The water status of plants was established by measuring relative water content (RWC) of leaves. Chlorophyll fluorescence induction method was used to examine potential photochemical activity (Fv/Fm). Additionally, parameters of slow phase of chlorophyll fluorescence induction curve also were determined, such as 1-qP/NPQ. The values of 1-qP/NPQ characterised the intrinsic ability of PSII to balance photochemical and non-photochemical quenching. Measuring this parameter is a good tool for get information about stress plasticity of plants under non-optimal conditions.