The effect of the osmotic potential and specific ion concentration of the nutrient solution on the uptake and reduction of nitrate by barley seedlings

Abstract

Short-term absorption experiments were conducted with intact barley (Hordeum vulgare L.) seedlings to observe the effects of the osmotic potential (Ψπ) and salt species on nitrate uptake andin vivo nitrate reduction. The experiments consisted of growing barley seedlings for 5 days in complete nutrient solutions salinized to (Ψπ) levels of −0.6, −1.8, −3.0, −4.2, and −5.4 bars with NaCl, CaCl2 or Na2SO4. After the absorption period, the seedlings were separated into shoots and roots, weighed, then analyzed for NO3. The nutrient solutions were sampled for NO3 analysis each day immediately before renewing the solutions. The accumulative loss of NO3 from the solutions was considered to be uptake whereas NO3 reduction was the difference between uptake and seedling content. Lowering the (Ψπ) of the nutrient solutions resulted in decreased concentrations of NO3 in the plant, little or no effect (except at the lowest (Ψπ) level) on uptake, and increased nitrate reductase activity. Increased rates of NO3 reduction were in particular associated with the Cl concentration of the nutrient solution.