Carbon Dioxide and Temperature Effects on Pima Cotton Development
- K. Raja Reddy,
- Harry F. Hodges and
- James M. McKinion
Predicting plant responses to changing atmospheric CO2 and to the possible global warming are important concerns. Effects of CO2 on developmental events are poorly documented, as is the interaction of CO2 and other major climate variables on crop development. The objective of this experiment was to determine the effects of an altered CO2 environment and interactions of CO2 and temperature on pima cotton developmental rates. Pima cotton (Gossypium barbadense L. cv. S-6) was grown from seed in sun-lit plant growth chambers. Air temperatures were controlled from 20/12 to 40/32°C (day/night) in 5-degree increments. Daytime CO2 was maintained at 350 or 700 μL L−1. In a second experiment, the temperature was maintained at 30/22°C day/night and the plants were grown in 350, 450, or 700 μL L−1 CO2. Days required to develop nodes on the mainstem, days from emergence to first square, number of vegetative and fruiting branches, number of fruiting sites produced, number of bolls and squares produced, and number of bolls and squares retained by the plants were determined. Rates of mainstem node formation and the time required to produce the first square and first flower were not sensitive to atmospheric CO2, but were very sensitive to temperature. Prefruiting branch nodal positions required longer to develop than nodes with fruiting branches. Carbon dioxide levels did not affect the time required to produce nodes. Number of branches produced was sensitive to both temperature and CO2. The larger number of bolls set on the lower branches of plants grown at high CO2 provided a larger sink for photosynthate than plants grown at low CO2. This may be the reason for the observed reduction in number of fruit at the upper nodes of high-CO2-grown plants. More bolls and squares were produced and retained on plants grown in high-CO2 environments, except that none were produced in either CO2 environment at 40/32°C. Our results indicate that high-temperature-tolerant cotton cultivars would be more productive in the present-day CO2 world, and they would be essential in the future if global temperature increases.
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