Effects of salinity and ascorbic acid on growth, water status and antioxidant system in a perennial halophyte

Salinity causes oxidative stress in plants by enhancing production of reactive oxygen species, so that an efficient antioxidant system, of which ascorbic acid (AsA) is a key component, is an essential requirement of tolerance. However, antioxidant responses of plants to salinity vary considerably among species. Limonium stocksii is a sub-tropical halophyte found in the coastal marshes from Gujarat (India) to Karachi (Pakistan) but little information exists on its salt resistance. In order to investigate the role of AsA in tolerance, 2-month-old plants were treated with 0 (control), 300 (moderate) and 600 (high) mM NaCl for 30 days with or without exogenous application of AsA (20 mM) or distilled water. Shoot growth of unsprayed plants at moderate salinity was similar to that of controls while at high salinity growth was inhibited substantially. Sap osmolality, AsA concentrations and activities of AsA-dependant antioxidant enzymes increased with increasing salinity. Water spray resulted in some improvement in growth, indicating that the growth promotion by exogenous treatments could partly be attributed to water. However, exogenous application of AsA on plants grown under saline conditions improved growth and AsA dependent antioxidant enzymes more than the water control treatment. Our data show that AsA-dependent antioxidant enzymes play an important role in salinity tolerance of L. stocksii.Higher Education Commission of Pakistan for provision of funds under a research grant entitled ‘Salt-induced Oxidative Stress: Consequences and Possible Management’

Effect of Aluminium Stress on Germination and Mineral Nutrition of Kidney Bean Cultivars with Different Sensitivity to Aluminium

Aluminium is the most important element in the soil as a stable complex with oxygen and silicates. When pH is below 5, aluminium dissolves in soil water and is absorbed by plant roots. Aluminium toxicity is a major constraint to agricultural production in the world, because 50% of the world's potential lands are acidic. Hence this study was conducted to investigate the toxic effects of aluminium on the germination and nutrient uptake in five cultivars of kidney beans (Derakhshan, Goli, Akhtar, Sayad and Naz) at three concentrations (30, 40, and 50mM) aluminium nitrate, Al(NO 3 ) 3 . Due to aluminium toxicity, reduced germination and growth of seedlings was recorded in all cultivars. Absorption of various nutrients, such as Fe, Ca, Mg, K, p, N decreased in roots and shoots of all cultivars. P and Mg Contents of shoots were less affected in all cultivars. Two cultivars including Derakhshan and Goli were better in terms of growth and accumulation of minerals than the other three. In General, germination and nutrient accumulation was inhibited in kidney bean due to the presence of aluminium