Studies on the response of nitrate reductase to salinity and water stress in two varieties finger millet (Eleusine Coracaria (L) Gaertn)
Gisesa, William N. Obiero
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Among the various biochemical factors responsible for growth, the enzyme nitrate reductase is of major importance. It is the rate limiting enzyme in the reduction of nitrate to ammonia. Nitrate reductase activity is influenced by a variety of environmental factors including water and salt stress. Since this enzyme is important in assimilatory nitrate reduction, the effect of water and salt stress on its activity is of prime importance in crop plants. In the present study, the effect of salinity on the germination of seeds, plant growth and development, and nitrate reductase activity in the two varieties of finger millet was investigate. The effect of salinity and water stress on nitrate reductase activity during the different stages of development was also evaluated. An attempt was also made to study the effect of increasing levels of salinity on callus growth. These experiments were set up in the laboratory, green house and the tissue culture chamber. Two cultivars of finger millet (KAT/FM-1 and ENKA) were subjected to water stress and increasing levels of salinity. Growth, nitrate reductase activity and tissue nitrate content were monitored during the tissue nitrate content were monitored during the different stages of development (2 to 14 weeks). It was observed that salinity reduced the rate and percentage germination. Salinity reduced linear growth of the roots and shoots, seedling dry weight and /or had no effect on tissue soluble protein content in the two cultivars. Salinity reduced nitrate reductase activity and the tissue nitrate content. It was also observed that water stress adversely affected nitrate reductase activity and it also led to a reduction in tissue nitrate content. The tissue culture studies showed that increased levels of salinity reduced callus growth. However, the battery of these experiments demonstrated clearly that both varieties have some degree of salt resistance. The studies have clearly unfolded the truth that these varieties are somewhat tolerant to drought and salinity conditions. Field studies under controlled conditions shall be necessary before any variety is recommended to farmers in the arid and semi-arid regions of this country.