EFFECTS OF ROOT TEMPERATURE ON GROWTH OF CROP PLANTS

研究了不同硝态氮/铵比条件下番茄对恒定和可变根温的反应。在其它环境条件不变的情况下，番茄根温分别为12/12、16/8和20/20 ℃。研究了低温根温对番茄蒸腾作用、生长、木质部汁液中矿质元素、可溶性碳水化合物和养分的离子平衡以及赤霉素和细胞分裂素含量的影响。结果表明，12 ℃和16 ℃的低温日根温显著降低了番茄的蒸腾作用和生长（地上部干重分别提高47和26%，根干重分别提高36和14%，地上部硝酸盐分别提高79和50%，根硝酸盐分别提高49和16%，根木质部分泌物中的细胞分裂素水平分别降低27%和13%，赤霉素水平分别降低65%和23%。可溶性碳水化合物在地上部和根系中的含量显著增加（18 a 关于我们 nd 111%。因此，根温状况是通过影响番茄生长而影响番茄生长的.因此，根温状况是通过影响番茄的各项生长参数来影响番茄生长的.根温在8 ~ 16 ℃范围内波动比根温在12 ℃范围内恒定更有利于番茄生长。水分吸收问题，由于水的粘度和膜透性的变化，气孔关闭有直接的影响。根中细胞分裂素和赤霉素的产生在低温下比在高温下低。激素从根向地上部的运输受昼夜实际根温而不是平均根温的控制。低根温对芽生长的主要影响来自植物激素和硝酸盐向顶部的缓慢运输，而不是分别降低其生物合成速率或进入根部。少

Response of tomato (Lycopersicon esculuntum) supplied with vary ratios of nitrate/ammonium to constant and variable low root temperature were studied. Root temperatures (12/12,16/8 and 20/20ﾟC day/night) were set for tomato, where other environmental conditions were constant. The effects of low root temperature on transpiration, growth, ionic balance of total and of water soluble mineral elements, soluble carbohydrates and nutrient concentration as well as gibberellins and cytokinin levels in xylem sap are determined.Tomato results showed that low day root temperatures of 12 and 16ﾟC reduced, significantly, the transpiration and growth (shoot dry weight by 47 and 26%, root dry weight by 36 and 14%, shoot nitrate by 79 and 50%, root nitrate by 49 and 16%, levels of cytokinins in root xylem exudate by 27 and 13% and gibberellins by 65 and 23%) in relation to the respective values of 20ﾟC day root temperature. Soluble carbohydrates in the shoot and roots were increased significantly (18 a … More nd 111%) by 12ﾟC root temperature. In conclusions root temperature regime affects tomato growth by its influence. In conclusions root temperature regime affects tomato growth by its influence on various growth parameters. Fluctuating root temperature in the range 8 to 16ﾟC is more favorable for tomato growth than constant root temperature at the same average of 12ﾟC.The temperature effect can not be explained, only, on the basis of nutrient transport or nitrogen metabolism. Water uptake problems, due to changes in water viscosity and membrane permeability, has a direct effect on stomatal closure. Cytokinin and gibberellin production in the root is lower at low than at high root temperatures. Hormones transport from the root to the shoot is controlled by the actual root temperature during day and night and not the average root temperature. The main effects of low root temperatures on shoot growth stem from slow transport of plant hormones and nitrate to the top rather than reduction in their rate of biosynthesis or entry to the root, respectively. Less