the effect of salinity and nitrogen deficiency on the changes in selected physiological parameters of common bean (phaseoleus vulgaris l.) grown in hydroponic cultures

Abstract

This study aimed at evaluating the physiological activity of common bean grown under the conditions of stress being induced by salinity and nitrogen deficiency and its lack in substrate. Three series of two-factorial hydroponic experiment with the common bean (Phaseolus vulgaris L.) cultivar Basta were carried out from May to July in 2013–2014. The first experimental factor was three levels of nitrogen content in a Hoagland hydroponic medium (level 1 – a complete medium, level 2 – without 50% N, level 3 – without 100% N). The second experimental factor was three levels of medium salinity (level 1 – no NaCl addition, level 2 – 30 mM NaCl addition, level 3 – 50 mM NaCl addition). Nitrogen deficiency in a Hoagland hydroponic medium, together with increased salinity level, significantly affected the changes in the physiological parameters of the common bean cultivar Basta being tested, i.e. assimilation pigment concentration (chlorophyll-a, chlorophyll-b and chlorophyll-a+b and carotenoids), assimilation and transpiration intensities, and RWC (relative water content). The 50% nitrogen deficiency in medium induced a significant increase in the concentration of all assimilation pigments in common bean leaves and was by far the highest among the experimental variants being tested. A significant decrease in the content of assimilation pigments was observed in the hydroponic mediums without nitrogen and salined with 30 and 50 mM sodium chloride. The interaction of these two experimental factors being analysed, i.e. nitrogen deficiency and its lack in a Hoagland hydroponic medium and its salinity, significantly decreased the intensity of assimilation in bean leaves, while a significant increase in transpiration was observed in the variant without nitrogen and with 50 mM NaCl. The experimental variants being tested had a significant effect on the changes in leaf water balance of the common bean cultivar being tested. Salinity, in interaction with nitrogen deficiency in medium, decreased relative water content (RWC) in leaves, irrespective of their level.