EFFECTS OF ROOT TEMPERATURE ON GROWTH OF CROP PLANTS

研究了不同硝铵配比下番茄（Lycopersicon esculuntum）对恒低温和变低温的响应。在其他环境条件不变的情况下，番茄的根温（12/12、16/8和20/ 20oc）被设置为白天/晚上。测定了低根温对木质部汁液蒸腾、生长、总离子平衡、水溶性矿质元素离子平衡、可溶性碳水化合物离子平衡、养分浓度以及赤霉素和细胞分裂素水平的影响。结果表明，相对于20 C日根温，12和16 C日根温显著降低了番茄的蒸腾和生长（茎干质量降低47%和26%，根干质量降低36%和14%，茎硝态氮降低79%和50%，根硝态氮降低49%和16%，根木质部分泌的细胞分裂素降低27%和13%，赤霉素降低65%和23%）。在12℃的根温下，茎部和根部的可溶性碳水化合物含量显著增加，分别增加了18 ~ 111%。综上所述，根温制度通过对番茄生长的影响来影响番茄的生长。综上所述，根温制度通过对番茄各生长参数的影响来影响番茄的生长。在8 ~ 16 C范围内波动的根温比在12 C范围内恒定的根温更有利于番茄的生长。温度效应不能用养分运输或氮代谢来解释。水分吸收问题，由于水的粘度和膜的通透性的变化，有直接影响气孔关闭。根中细胞分裂素和赤霉素的产量在低根温度下比在高根温度下要低。激素从根到茎的运输受昼夜实际根温控制，而不是平均根温。低根温对茎部生长的影响主要来自于植物激素和硝酸盐向植株顶部的转运速度减慢，而不是它们的生物合成速度减慢或进入根部的速度减慢。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