ABSTRACT
Plant responses to drought often have been quantitatively and even qualitatively different in controlled environments from the responses observed under most natural field conditions. Important information on the range of plant responses to environment and their adaptation can be obtained by comparing the function and development of the same set of genotypes growing in several contrasting field environments. In controlled environments such as greenhouses, growth chambers, or gas-exchange cuvettes, one can vary individual environmental factors while keeping other factors constant. Controlled environments can be used for conducting unique single-factor experiments that provide important information on the causes of specific plant responses to environment, and the experiments can be repeated permitting rigorous testing of the validity of the results. Nutrient limitations and reduced rooting volume may both contribute to the down-regulation of photosynthetic capacity that can occur when C3 plants growing in small pots are subjected to elevated atmospheric.
