ABSTRACT

Cotton seeds (Gossypium hirsutum L.) were planted in 15 1 pots in greenhouse, April 20, 1992. The carbon dioxide was injected in two greenhouses beginning April 26, 1992 (when 50% percent of the seedlings emerged) and continued until July 21, 1992 from 06:00 h through 19:00 h at a set point of 550 " 75 ìmol mol^-1. The temperature in each greenhouse was gradually increased at 2-hour time step to mimic day and night temperatures of Arizona during cotton growing season (based on five years temperature record in Phoenix, AZ). Two greenhouses were maintained at high CO₂ x high temperature (40EC day/32EC night); high CO₂ x low temperature (32EC day/22EC night); and the other two greenhouses were maintained at ambient CO₂ atmosphere with high and low temperatures as described for high CO₂.

Plant height increased significantly with increased air temperature and high CO₂. Fully expanded leaves were larger in CO₂-enriched plants at each leaf position. The biomass production at high CO₂-high temperature environment increased significantly however, production of squares and bolls per plant increased at low temperature with enriched CO₂. The effect of temperature on growth, development, and yield of bolls followed a similar trend in ambient CO₂ as in high CO₂ atmosphere. Water was however, conserved in low Temperature plants grown at enriched CO₂-environment; as transpiration rate remained lower in this environment than high temperature plants grown under the same environment.