ABSTRACTCOMPREHENSIVE studies of plant dynamics re-quire simultaneous measurements of plant roots and tops in a controlled environment. The objectives of this research were to design, construct, and test a computer-controlled environmental system for studying whole-plant responses. Three independently controlled and monitored sunlit chambers, the Soil-Plant-Atmosphere Research (SPAR) system, were constructed attheUSDA-SEA, Coastal Plains Soil and Water Conservation Re-search Center, Florence, SC. Each SPAR unit is a base steel soil bin, (2 x 0.5 x 1 m) on top of which is an acrylic plastic aerial chamber (1.5 m high), secured and sealed to the base. The temperatures of the aerial chamber and the soil bin can be controlled independently by air-conditioners and heaters. Micrometereological, soil, and plant variables are measured automatically with a micro-processor-based digital data acquisition system. In each chamber, COz can be measured each minute to determine the amount of C02 absorbed by the plant, which must be replaced to maintain a constant C02 level. Apparent net photosynthesis is calculated from C02 measurements and corrected for chamber leakage. The SPAR system was evaluated using cotton to de-termine the potential amount of root dry matter accumu-lation and proliferation in the soil under constant soil matric potential and non-limiting photosynthate supply. Initial results indicated that the SPAR system provides a precisely controlled soil and aerial environment to accurately and rapidly measure automatically some plant stresses and growth rates. Dependence of these rates on incoming energy indicates the need to rapidly and continuously measure soil-plant-atmosphere pro-cesses, because integration of these measurements for long periods tends to mask these responses.