Environmental Controls on the Growth and Yield of Okra. I. Effects of Temperature and CO2 Enrichment at Cool Temperature1

Growth and yield responses of okra (Abelmoschus esculentus(L.) Moench, cv. Clemson Spineless) to 6 different day/night temperature regimes and 3 CO2concentrations were studied in controlled environment chambers of the Duke University Phytotron. The objective of these experiments was to characterize the effects of temperature and CO2concentrations on vegetative growth and fruit yield of okra. The day/ night temperature regimes in the greenhouses at ambient light and CO2concentration (350 ppm) were: 17/11, 20/14, 23/17, 26/20, 29/23 and 32/26 C, and the CO2concentration in the growth chambers at 20/14 C were 450, 675, and 1,000 ppm. In the experiments at ambient CO2concentration, no plants survived at temperatures below 26/20 C. The plants grown at 26/20 C and higher temperatures in the greenhouses grew to maturity and produced fruits. Under CO2enrichment in growth chambers, however, the plants survived to maturity at 20/14 C. Thus at the suboptimal temperature of 20/14 C, CO2enrichment compensated for the adverse effects of cool temperature on the growth of okra. The chamber grown plants at 20/14 C produced the maximumd ry weight in 1,000 ppm CO2. The greenhouse grown plants under ambient CO2and light produced the greatest dry weight at 32/26 C. The results demonstrate why okra is not a productive crop at mean temperature of 26/20 C or below in ambient CO2concentration. However, at increasing atmospheric CO2levels okra becomes much more vigorous and productive at low temperature and therefore may spread into cooler areas if the global atmospheric CO2concentration continues to increase.