Enhancement of Growth and Quality of Winter Watermelon Using LED Supplementary Lighting

The effect of LED supplementary lighting at various intensities on winter-grown watermelon plants was evaluated to identify the optimal level for enhancing growth, yield, and quality. The plants were exposed to three lighting conditions: natural daylight (control) and LED supplementary lighting at 900 and 1500 µmol/m2/s, from 17:00 to 21:00. Supplemented LED lighting enhanced chlorophyll content, Ca2+ and Mg2+ in the leaves of fruit set region, leading to an increase in photosynthesis rate throughout the growing period and supporting consistent plant growth. The results showed that LED900 µmol/m2/s significantly boosted the number of female flowers, fruit weight, size, and flesh thickness. Ultimately, the yield per plant increased by 31% under the LED at 900 µmol/m2/s and by 14% under the LED at 1500 µmol/m2/s compared to the control. Furthermore, high sugar and low acid contents were detected in the LED-treated fruits. These results indicate that fruits bore under LED lighting ripened faster than those in the control. In conclusion, supplemental LED lighting markedly contributes to watermelon production during winter, with a 900 µmol/m2/s LED light intensity outperforming 1500 µmol/m2/s in promoting plant growth and boosting the yield and quality.