CARBON-DIOXIDE AND TEMPERATURE EFFECTS ON PIMA COTTON GROWTH

Temperature and CO2 are major environmental variables that affect plant growth and development. Limited information is available concerning how these factors affect plants, as well as specific interactions between the two. We conducted two experiments in controlled environmental chambers were temperature and CO2 were controlled and other environmental factors were not limiting. The purpose was to determine how cotton grew and responded to a range of temperatures and CO2 concentrations. During vegetative development, stem growth was quite sensitive to CO2 resulting in more effective early-season light capture. Plants did not develop more nodes when exposed to additional CO2, while node number increased more at higher temperatures. Individual leaf growth was about 18% greater at optimum temperature in 450 mul 1(-1) than in 350 mul 1(-1) CO2, but did not increase from 450 mul 1(-1) CO2 to 700 mul 1(-1) CO2. However, the time required for a leaf to reach mature size was not influenced by CO2. Leaf area, on the whole plant basis, was about 33% greater on plants grown at optimum temperature in high CO2 than in ambient CO2. The greater leaf area on a whole plant basis was achieved by a combination of larger leaves and additional leaves produced primarily on the branches. There was a 28% increase in number of bolls produced at 700 mul 1(-1) CO2 at optimum temperature compared with bolls produced at 350 mul 1(-1) CO2. There was not, however, an increase in boll size due to high CO2. At 35.5-degrees-C, little growth response to high CO2 environments occurred at 700 mul 1(-1) CO2 compared with 350 mul 1(-1) CO2, but approximately a 45% increase occurred in the plants grown at 18.9-26.9-degrees-C. Less total biomass was produced at 35.5-degrees-C than at 26.9-degrees-C and no bolls were produced in either CO2 environment at the higher temperature. The most important response to temperature and CO2 occurred at high temperatures where the effects of elevated CO2 on plant growth were masked by apparent high-temperature injury that limited growth of all plant organs, particularly, reproductive growth.