NaCl—induced modifications of nitrogen absorption and assimilation in salt tolerant and salt resistant millet ecotypes (Pennisetum typhoideum L. Rich.)

Abstract

It has been estimated that one-third of the irrigated areas of the world is affected by salinity and increasing salts in the soil represent the major limitation to crop yield in many arid countries5. Although salinity is not incompatible with plant life, only a few crops are able to grow under high level of salts accumulated by fertilization practices or by use of saline water for irrigation. Since the salt-free water available for irrigation purpose is difficult and expensive to obtain, a promising approach to overcome the problem of salinity may be the genetic improvement of salt tolerance in crops by: 1) selection among agronomic cultivars; 2) hybridization and ploidy changes; 3) use of wild germplasm sources to develop new cultivated species. Promising studies have been undertaken with barley, tomato, wheat and wheatgrass4,10,16,17. Salt stress in plants can be accounted for an increase in sodium, chloride or both ion contents9 and a decrease of the internal nutrient availability2,6. The consequent changes in plant metabolism are mainly on enzyme systems which can be repressed or inhibited, induced or activated7,8,14,19. Comparative studies on varieties of crop plants differing in salt tolerance appear useful. Millet (Pennisetum typhoideum L. Rich.) is one of the widely cultivated crops in African and Asian regions.2