Growth of Roots of Seven Varieties of Spring Wheat at High and Low Moisture Levels1

Abstract Seven varieties of spring wheat, T. aestivum L., were grown at two levels of moisture in glass‐faced boxes. Weekly measurements, made of the roots showing on the glass, and the total weight at each depth were required to determine the root pattern. Four of the varieties were grown in both Weyburn Oxbow Loam and Regina Heavy Clay. Yield of ‘Thatcher’ was reduced less by moisture stress than that of other varieties. Roots of Thatcher penetrated the soil more quickly in dry soil than in wet soil and more quickly than other varieties tested at both moisture levels. When soil dried out in surface layers, root growth of Thatcher increased in the moist layer just below. Two lines developed for the Canadian Prairies were similar to Thatcher but yielded slightly less when moisture stress was high. ‘Nainari 60,’ ‘Lemhi 53,’ and especially ‘Koga II’ produced more roots at high levels of moisture than Thatcher but suffered more under moisture stress. ‘Narino 50’ was earlier and lower yielding but suffered less from moisture stress than most varieties tested. The pattern of roots of the different varieties help to explain their yield performances at different moisture levels. The loam soil was more satisfactory to use in root studies than the clay soil, as it tended to accentuate the differences in response to high and low levels of moisture.