EFFECT OF PLANT GROWTH REGULATORS ON FEMALE FLOWER DEVELOPMENT AND PRODUCTIVITY OF WATERMELON PLANTS GROWN DURING WINTER SEASON WITH LOW-TECH GREENHOUSE

Temperature generally falls below the threshold limit of the watermelon plants during the winter which is a prime hindrance to cultivate it in this season in Bangladesh. Although low-tech greenhouse which made of bamboo or wooden structure and polyethylene film as a cladding material significantly increases temperature, but watermelon plants grown under low-tech could not initiate pistillate flowers rather than sufficient vegetative and male flower development were observed. The present study was carried out under the low-tech greenhouse from middle of October 2017 to middle of February 2018 in the Field Laboratory, Department of Crop Botany, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh to investigate whether the some plant growth regulators (PGRs) like ‘ethephon’ and ‘flora’ could develop the female flowers and fruit setting with fruit yield in four varieties of watermelon viz. Sonya, Black Dorin, Badsha and Dragon. The watermelon plants grown both in low-tech plants and that at outside were treated (sprayed) at earlier development stages with (i) no PGR (control), (ii) Flora, and (iii) Ethephon. Air and soil temperatures increased inside the low-tech than that aside outside which significantly hastened all the phenophase events like appearance of first vine, leaf, male and female flowers. Both the PGRs exerted the positive effect on the female flower development and fruit setting as well as yield components and fruit yield. However, the effect of ethephon was found as satisfactory. Therefore, it is concluded that spraying of ethephon at earlier growth stages could offer satisfactory fruit yield of watermelon under low-tech greenhouse during winter season in Bangladesh. The output is a combine effect where low-tech offers warmer microclimate for sufficient vine growth and development, and ethephon induces female flowering leading to get satisfactory fruit yield.