Nutrient uptake by wheat seedlings that differ in response to mixed nitrogen nutrition¹

In hydroponics, cereal crop growth is usually enhanced when the nutrient media contains both nitrate and ammonium compared to either form separately. Identification of genotypic variation between two spring wheat cultivars (Triticum aestivumcv. Len, and Triticum durumcv. Inbar) in their magnitude of growth response to mixed N permits a comparative evaluation of metabolic processes underlying enhanced growth from utilization of N mixtures. The objective of this study was to determine if the additional mixed N-induced growth, and the difference in response between cultivars, is associated with the uptake or partitioning of N, P, or K during the seedling stage of development. Plants of Len and Inbar were grown hydroponically for 21 days in nutrient solutions containing N either as all nitrate or as a 50/50 mixture of nitrate and ammonium. The mean of three experiments showed that whole plant dry weight increased 19% for Len and 41 % for Inbar when the plants were supplied with the N mixture compared to only nitrate. With the N mixture, the increase in biomass was almost entirely due to enhanced shoot production, which was mainly the result of greater tiller formation. Both cultivars absorbed more N, P, and K when grown with mixed N, and the additional N and K uptake.