SPAR—A Soil-Plant-Atmosphere Research System

Abstract

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…