Chilling injury in okra (Hibiscus esculentus L.) in relation to plant development and nitrogen metabolism

Summary Okra plants were exposed to chilling temperatures of 5° or 10°C for various periods up to 144 hours in a controlled environment room. Controls were maintained in a similar room at 25°C. Seedling plants which had developed five true leaves and plants in a preflowering condition with well developed buds were used. Results showed that injury occurred at both 5° and 10°C in plants at both growth stages. Seedling plants exposed at 5°C for 144 hours were killed while the older ones died back to the lower nodes. Eventually growth occurred from the buds at these nodes. In cases where the plants survived there was a delay in flowering and a decrease in the total number of flowers. Increased cold exposure resulted in an increased percentage dry matter. It appeared that increased dessication contributed to injury, but that atmospheric humidity itself had little relationship to injury. The insoluble nitrogen fraction did not show any great change. There was an increase in some amino acids, and it was noted that these were the same as those derived from pyruvate. The soluble protein fraction did not change. It was suggested that this lack of change might be a manifestation of the difference between plants that can be hardened and those that cannot.