Humic acid application alleviate salinity stress of bean (Phaseolus vulgaris L.) plants decreasing membrane leakage

Abstract

The effect of varying humic acid supplies (0, 0.05 and 0.1% w/w) on some agro-physiological properties and ionic balance of bean plants in different salt source and doses were investigated. Plants were treated with eight salt sources [sodium chloride (NaCl), sodium sulphate (Na2SO4), calcium chloride (CaCl2), calcium sulphate (CaSO4), potassium chloride (KCl), potassium sulphate (K2SO4), magnesium chloride (MgCl2) and magnesium sulphate (MgSO4)] in four different concentrations (0, 30, 60, and 120 mM doses) for 60 days in a growth media. The highest salt doses; 120 mM of NaCl, CaCl2, MgCl2 and KCl2 at no humic acid applications caused plant death, but no plant death was obtained in humic acid application (0.05 and 0.1%) doses in all of the salt types and doses except for CaCl2. Total chlorophyll and nitrate contents of plants decreased with increasing salt doses, but were negatively related to humic acid application doses. Proline contents of plant were increased with increasing salt doses and the highest value was obtained for NaCl application. The effects of salt concentrations in nitrogen and phosphorus content of plants were significant. Humic acid added to saline soil significantly improved the variables affected by high salinity and also increased plant nitrate, nitrogen and phosphorus, reduced soil electricity conductivity, proline and electrolyte leakage of plant, enhanced plant root and shoot dry weight by allowing nutrients and water to be released to the plant as needed. The result suggested that humic acid have great potential in alleviating salinity stress on plant growth and growth parameter in saline soils of arid and semi-arid areas. This humic acid appeared to be highly effective for soil conditioners in vegetable growth, to improve crop tolerance and growth saline conditions. Key words: Arid soil, electrolyte leakage, leaf area, nitrate, proline, total chlorophyll, salt stress.