Responses of young maize plants to root temperatures
1963
Grobbelaar, W.P.
The effect of root temperatures on growth, water uptake and ion uptake of the maize single cross K <sub>64r</sub> X E <sub>184</sub> has been studied during the early vegetative phase in culture solution in temperature-controlled rooms. A root temperature range of 5°-40°C with 5°C increments, a constant air temperature of 20°C, and a constant light intensity were employed throughout.The optimum temperature range for root growth was found to be 20°-30°C (distinctly less at 35°C, mainly by less seed-root growth), that for shoot growth 25°- 35°C. The influence of root temperature on shoot apices was also estimated. Leaf initiation and elongation were most rapid between 25° and 35°C, as also the total leaf length per plant. The longest ultimate individual leaf size was however reached between 15° and 25°C. An attempt was made to explain the influence of temperature on content of dry matter and water-soluble carbohydrate in roots and shoots. Root temperature influenced the relation root/shoot. An analysis of the net assimilation rate, transpiration rate and rate of ion uptake and proportional growth revealed interesting relations. The differences in proportional growth were associated with the proportional leaf area per plant. Root temperature did affect the uptake of NO <sub>3</sub> -, P, K, Ca and Mg. The influence of the internal diffusion pressure deficit on growth rate was also considered.
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