Growth and development of seminal and crown roots of wheat seedlings as affected by temperature

The experiment was conducted to determine the optimum temperature for root growth of wheat seedlings (Triticum aestivum L.), and to evaluate the effects of temperature on growth and development of seminal and crown roots. Wheat seedlings were grown in a controlled environmental growth chamber and were harvested on alternate days for about 30 days beginning at 4 days after planting (DAP). The number of seminal and crown root axes and the length of each seminal and crown root axis, as well as the days after planting when the root axes and shoots were first observed, were recorded. Dry matter production of shoots and of seminal and crown roots was determined for air temperatures of 10, 20, 25 and 30°C. Some seminal root axes had already appeared at 4 DAP when sampling started, but their lengths were different at different temperatures. Shoots and crown roots emerged much earlier at 25 and 30°C than at 10 and 20°C. The 30°C temperature restricted formation of seminal root axes. The 10°C temperature retarded emergence and elongation of crown root axes. Lengths and dry matter production of both seminal and crown roots increased gradually to a maximum as temperature increased to 25°C, then declined at a temperature of 30°C. Root to shoot ratios were significantly greater and specific root lengths were significantly less at 10°C than those at 20, 25 and 30°C. Wheat grown at 25°C had the most extensive root system.