End-of-Day Light Treatments Regulate Watermelon Seedling Growth with No Subsequent Effects on Fruit Production After Transplanting to the Field

Abstract

While using end-of-day (EOD) red or far-red (FR) light had been previously successful in regulating the seedling growth of selected vegetable transplants, no study has evaluated this transplanting regulating technique for watermelon, or whether it has effects on fruit production after the seedlings are transplanted to the field. As such, the influence of end-of-day (EOD) red (R) or far-red (FR) light on watermelon [Citrullus lanatus (Thunb) Matsum and Nakai], cv. Sugar Baby, seedling growth and subsequent fruit production after transplanting to the field was investigated. Seedlings were exposed to low intensity EOD R (15 min), EOD FR (15 min), EOD FR + R (15 min of FR followed by a 15 min of R treatment), or no EOD light (control) treatments at the end of each photoperiod to determine if these light treatments affected plant growth in a manner that might be beneficial for transplant production (e.g., shorter more stocky plants that might be less prone to lodging and more easily used with mechanical transplanters, or larger taller plants that might have greater early growth after transplanting) without deleterious effects on subsequent fruit production. EOD FR treated seedlings had longer petioles and internodes than seedlings in any of the other EOD R and EOD FR + R or control light treatments. EOD R treated seedling growth was not different than control seedlings. The EOD FR + R treatment negated the EOD FR light growth effects suggesting involvement of phytochrome in the light regulated growth of watermelon seedlings. When EOD treated watermelon seedlings were transplanted to the field there were no subsequent effects on fruit production.

Key Words:

• Citrullus lanatus
• light
• phytochrome
• photomorpho-genesis
• red (far-red) light