Effect of Reduced Temperatures on Melon Transplant Subsequent Growth and Survival

Abstract

Delays in transplanting vegetable seedlings are often a problem due to cold, wet spring weather. This results in the production of overgrown transplants, which are more difficult to transplant and often do not survive. The objective of this study was to find a non-chilling temperature at which to short-term-treat transplants in order to slow down vegetative growth. `Superstar' muskmelon and `Royal Jubilee' watermelon seedlings were greenhouse-grown at 20°C during Mar. 1996. Fifty-cell trays of transplants were grown to the first true leaf stage and then held in a dark cooler at 7.5 or 12.5°C for 4 to 8 days. Control plants were kept in the greenhouse. Transplants were repotted into larger pots after the treatment. Preliminary experiments revealed that 8 days of 7.5°C was too severe of a temperature for watermelon and cantaloupe transplants. Six days of 7.5°C was effective in significantly reducing stem and leaf area growth without seedling death for both types of melons. Shorter durations at 7.5°C or the same duration at 12.5°C was less effective in retarding stem elongation. Surface area of the transplant leaves, after the reduced temperature treatment and subsequent growth, was much more sensitive to a drop in temperature and the length of temperature treatment. In 1997, these treatments will be repeated in the greenhouse and also in the field.