Genetic differences among barley cultivars and wild oat lines in endogenous seed nutrient levels, initial nitrate uptake rates, and growth in relation to nitrate supply

Abstract

1. Net NO₃ ^‐ uptake rates and internal root NO₃ ^‐ contents were studied in 9 barley (Hordeum vulgare L.) varieties and 5 genetically pure lines of wild oats (Avena fatua L.). Significant differences in net NO₃ ^‐ uptake rates and [NO₃ ^‐]_e were found among barley cultivars while the NO₃ ^‐ uptake rates were only significantly different amoung wild oat lines. No correlation existed between net NO₃ ^‐ flux and [NO₃ ^‐]_i in barley cultivars.

2. Net NO₃ ^‐ uptake isotherms were determined for 3 barley varieties, Compana, Fergus, and Betzes, and 3 wild oat lines, CS40, AN51, and SH319. Kinetic constants V_max and K_m, calculated for uptake rates of selected cultivars, indicate that net NO₃ ^‐ flux was generally higher for Compana than Fergus and Betzes. Although the wild oat lines had similar NO₃ ^‐ flux rates at higher [NO₃ ^‐]_e levels, CS40 had a higher net flux at lower nutrient levels.

3. Variations in growth characteristics were seen between 9 barley varieties and 5 wild oat lines at 4 different [NO₃ ^‐]_e levels (25, 50, 100, and 200 μM [NO₃ ^‐]_e). Variations were more apparent with the biomasses of the cultivars compared with the nutrient contents, suggesting that the intervarietal differences were not so much due to internal total nitrogen but the biomass of the plant.

4. Significant differences were seen among barley cultivars and among wild oat lines in seed N, F, and K levels. There was no correlation between the rankings of the seed N content and the growth at 25, 50, 100, or 200 μM [NO₃ ^‐]_e between barley cultivars or wild oat lines in our hydroponic system.