Fundamental Studies on Optimization of Environment in Plant Production

以黄瓜和甘薯为试材，分析了环境对植株水分关系、根系生理功能和光合产物运转的影响，以期为植物生产环境优化提供数据库。利用环境因子和叶片特性定量定义了蒸发需求（艾德）及其对植物水分关系的影响（Imp）。艾德和Imp的动态与植物水分平衡、气孔运动、叶片生长、干物质生产和水分利用效率直接相关，这表明控制艾德和Imp对优化植物水分关系是可行的。本文介绍了一种新研制的密闭水培环境控制系统，用于根系呼吸、吸水速率的测定和^<18>O_2示踪。在黑暗条件下，空气O_2促进了缺O_2营养液中根系的吸水，并与根系呼吸同步进行。结果表明，在<18>缺O_2营养液中，空气环境中的O_2是通过根系呼吸来释放的。这些事实表明，在缺O_2的根环境中，黄瓜植株通过叶片进行根呼吸，从而提高了水分的吸收。在同化物运转方面，我们开发了两种新的培养系统来分析环境对库-源关系的影响：（1）沙培系统，其中库和源环境可以独立控制;（2）溶液-空气培养系统，其中通过将块根保持在空气空间中而将须根保持在营养液中来分离储存库和利用库。在这些系统上，对块根生长的最佳温度和湿度条件进行了研究。新建立的方法学可为植物环境优化提供定量数据库。

Environmental effects on whole plant water relations, root physiological functions and translocation of photoassimilates were analyzed by using cucumber plants and sweet potato plants with the view of integrating data base for environmental optimization in plant production. Evaporative demand (ED) and its impact (Imp) on plant water relations were defined quantitatively by using environmental factors and leaf characteristics. Dynamics of ED and Imp directly related to plant water balance, stomatal movement, leaf growth, dry matter production and water use efficiency, and this suggests the applicability of control of ED and Imp for optimizing plant water relations. An environment control system of airtight hydroponics was newly developed for measurements of root respiration and water uptake rates and for ^<18>O_2tracing. Root water uptake in O_2-deficient nutrient solution was promoted with aerial O_2 in darkness, and appeared simultaneous in dynamics with root respiration. It was found that ^<18>O_2 applied to aerial environment is respired by root respiration in O_2-deficient nutrient solution. These facts suggest that aerial O_2is transported through leaves for root respiration in cucumber plants grown in an O_2-deficient root environment, and this results in improvement of water uptake. On translocation of photoassimilates, two culture systems were newly developed for analyzing environmental effects on sink-source relationships : (1) a sand culture system where sink and source environments can be controlled independently : (2) a solution-air culture system in which storage sink and utilization sink are separated by keeping tuberous root in air space and fibrous roots in nutrient solution. On those systems, the optimum temperature and humidity conditions for tuberous root growth were examined. The methodology newly established can be helpful for integrating quantitative data base for optimization of plant environments.