根系环境温度变化对根系吸水和叶片蒸腾的影响

木本植物银合欢(Leucaena leucocephala (Lam.) de Wit.)和禾本科植物玉米(Zea map L.)为材料，研究了根系温度变化对根系吸水和叶片蒸腾的影响。当根系周围温度从25°c降至15°c，短时间内(14 min)可显著促进根系的吸水和提高植株的蒸腾速度，这种促进作用随着低温处理时间的延长而消失。如将根系周围的温度又从15°c提高到25°c对根系的吸水和植株的蒸腾速度无明显的影响。低温处理短时间内(20 min)可提髙根系的水导和植株的蒸腾速度，但随着低温处理时间的延长，根系水导和植株的蒸腾速度迅速下降。低温处理30 min后显著促进根系ABA的合成，提高木质部ABA的浓度。外源ＡＢＡ处理根系显著降低叶片的蒸腾速度，但对根系的水导有促进作用。结果表明，处理初期低温对根系吸水和植株蒸腾速度的促进与根源ABA无关。

Effects of changes in temperature around roots on water uptake by roots and leaf transpiration were studied in Leucaena leucocephala (Lam.) de Wit., a subtropical woody plant species, and in Zea mays L. When the temperature around roots was rapidly lowered from 25 °C to 15 °C, the water uptake by the roots and leaf transpiration were stimulated significantly within a short period (14 min). However, this effect did not occur when the cooling time was prolonged neither did if occur when the temperature around the roots was resumed from 15 °C to 25 °C. Both the hydraulic conductivity of roots and leaf transpiration were increased substantially at first (within 20 min) and then decreased steadily to a level lower than those of the control in which the roots were continuous exposed to a low temperature (15 °C). Low temperature also promoted the biosynthesis of ABA in roots and enhanced the xylem ABA concentration, but such stimulation did not occur untill about 30 min after cooling treatment. Leaf transpiration was reduced markedly, but the hydraulic conductivity of roots increased when the root system was treated with exogenous ABA. It was suggested that some mechanisms other than ABA may be involved in the short-time cryo-stimulation of water uptake by roots and leaf transpiration.