ALLEVIATION OF SALT STRESS WITH POTASSIUM APPLICATION AND ROLE OF ANTIOXIDANT ENZYMES IN MAIZE

Abstract

Environmental stresses are among the most limiting factors to plant productivity. Among these, salinity is one of the biggest problems of Pakistan due to its arid to semi-arid climate. A rapid increase in demand for food due to increasing population, there is need to have salt tolerant crop genotypes in saline land for proper cultivation to meet this increasing demand. To investigate the effect of salinity on plant morphological, physiological and biochemical attributes and role of potassium in alleviating harmful effects of salinity in maize hybrids, two solution culture and one pot experiment were conducted. Initially, 9 maize hybrids were grown for four weeks in solution culture using three salinity levels (control, 50 and 100 mM NaCl). On the basis of biomass accumulation and K+/Na+ ratio, maize hybrids (26204, Hysun 33) and (8441, 33H25) emerged as salt tolerant and salt sensitive respectively. Subsequently, physiology and biochemistry of salt tolerant and salt sensitive maize hybrids were evaluated in solution culture and pot experiment under various levels of potassium and salinity. Results revealed that plant growth, RWC, MSI, chlorophyll contents and photosynthetic parameters of all maize hybrids decreased under salinity stress. But salt tolerant maize hybrids show significantly better plant growth relative to salt sensitive maize hybrids. Addition of potassium significantly alleviates the harmful effects of salinity by improving plant morphological, physiological attributes and enhancing antioxidant enzymes activities. The beneficial effects of potassium were more pronounced in salt tolerant maize hybrids than salt sensitive maize hybrids. Furthermore, salt tolerant and salt sensitive maize hybrids were grown in solution culture under salinity and heavy metal (Cd) stress. The results confirmed that salt tolerant maize hybrid 26204 is also Cd stress tolerant by showing better growth under both stress condition relative to maize hybrid 8441. Keyword: maize hybrid, salinity, potassium, antioxidant enzymes