Effects of salinity on growth, carbohydrate metabolism and nutritive properties of kikuyu grass ( Pennisetum clandestinum Hochst)

Abstract

The objective of this study was to investigate the effect of salinity on growth, nutritive properties and carbohydrate metabolism of Pennisetum clandestinum Hochst. Salt stress was induced by adding NaCl at different concentrations to the nutrient solution: 0, 50, 100, 150 and 200 mM. After 15 days under such stress, plants were actively growing up to 100 mM NaCl. Salinity affected root length more than leaf length. The invertase activity significantly enhanced in leaves and decreased in roots of kikuyu grass at 150 and 200 mM NaCl. In plants exposed to highest salt conditions, we observed an accumulation of hexoses and a lower activity of glucokinase (GK), phosphoglucoisomerase (GPI) and pyruvate kinase (PK). The glucose-6-phosphate dehydrogenase (G6PDH) decreased increasing salt concentration, showing at 200 mM NaCl the strongest reduction. The phosphoenolpyruvate carboxykinase (PEPCK) activity slightly and progressively increased in a concentration-dependent manner. Exposure of kikuyu grass to 150 and 200 mM NaCl caused an increase of NADP +-specific isocitrate dehydrogenase (IDH) activity in leaves and roots. The nutritive properties of kikuyu decreased in grass treated with 150 mM and even more with 200 mM NaCl. These data indicate that kikuyu is a grass tolerant to salinity up to 100 mM, suggesting its possible utilization in saline land where the survival of other fodder species is markedly reduced.