SENSITIVITY OF SHOOTS AND ROOTS OF YOUNG WATERMELON PLANTS TO END-OF-DAY RED AND FAR-RED LIGHT

The sensitivity of shoots and roots to end-of-day (EOD) red (R) or far -red (FR) light on growth of 'Sugar Baby' watermelon [Citrullus lanatu s (Thnnb.) Matsum & Nakai] was investigated. Plants mere grown in full -strength Hoagland solution and treated for 14 days to 15 minutes EOD light in trial 1 and in half-strength Hoagland solution and treated fo r 10 days to EOD light in trial 2. Exposing shoots to EOD FR resulted in elongated petioles of leaves 1 to 3 (as counted from the cotyledons ), internodes 1 to 3, and total stem length in both trials. Exposure t o EOD FR resulted in increased stem and petiole dry mass in trial 1, w hereas EOD FR resulted in increased root and leaf dry mass in trial 2. EOD FR exposure of roots increased the length of petiole 4 in trial 1 . In general, shoots were more responsive than roots to the growth-reg ulating effects of EOD ER.