Photosynthetic and growth responses of a perennial halophytic grass Panicum turgidum to increasing NaCl concentrations

Abstract

Several halophytes – plants which complete their life cycle in saline environment – have considerable economic potential as oil source, fodder, wood, ornamental, and medicinal plants. They may also serve as model plants to get insight in the mechanisms of salt resistance and with the future aim to develop halophytic crops. Panicum turgidum is, a C4 perennial halophytic grass, widely distributed in saline and arid areas of Pakistan with a considerable potential as a fodder crop because of its high palatability and nutritional values. The aim of this work was to determine growth, physiological and biochemical responses of P. turgidum by subjecting plants to varying concentrations of NaCl (0, 125, 250, 375 and 500mM) and to relate these data to photosynthetic parameters. When grown at low salinity (125mM NaCl) fresh and dry biomass (shoot and root) were similar to non-saline control. Photosynthetic parameters such as net photosynthesis rate, transpiration rate, water use efficiency, Fv/Fm, and electron transport rate correlated with growth response. High salinity led to a significant decrease of water use efficiency mainly because of an over proportional reduction of carboxylation rate arising from non-stomatal factors such as decreasing Rubisco and chlorophyll contents. Reduction of carboxylation rate at higher salinity caused oxidative stress, electrolyte leakage, high malondialdehyde (MDA) and H2O2 levels in addition to photo-inhibition and xanthine cycle dependent heat release.The data reported herein suggest that Panicum is a promising cash crop at low quality soils at moderate salinity. Its sustainable use can also help in desalinizing and reclaiming degraded land as well as sequestering CO2.