Abstract:

 Watermelon Jing xin No.4 and pumpkin Jingxinzhen No.4 were used as test materials, and LED pure white light was taken as control (CK). Five treatments were set, namely, red-blue light alternating at 1 hour interval (R/B1), red-blue mixed light (RB), red-blue light alternating at 6 hours interval (R/B6), pure blue light (B) and pure red light (R). Besides, experiments were carried out in a fully artificial light plant to delve into the optimal light formula for the growth and development of watermelon and Pumpkin seedlings. The results showed as follows: (1) the absolute growth rate of plant height, stem diameter and leaf area of watermelon seedlings under R/B6 treatment were increased by 77.2%, 110.7% and 68.5% compared with the control, respectively; the number of leaves of watermelon seedlings under R/B1 treatment was significantly increased by 78.6% compared with the control at 40d (P<0.05). Under R/B1 treatment, the absolute growth rate of pumpkin seedling height and the number of leaves at 40d after planting were significantly increased by 211% and 18% (P<0.05), respectively, and the absolute growth rate of stem diameter was increased by 85%. (2) The crude polysaccharide content of watermelon and pumpkin seedlings under R treatment was increased by 25.5% and 13.4% compared with the control (P<0.05), and the crude protein content of watermelon seedlings under B treatment was increased by 9.4% compared with the control, and the chlorophyll content of watermelon and pumpkin seedlings under RB treatment was higher than that under the control 10 to 40 days after planting. Watermelon and pumpkin seedlings treated with RB showed a 1.8% and 0.3% increase in chlorophyll content, respectively, on the 40th day after planting, compared to control plants. (3) At 40th day after implantation, PI_abs of watermelon seedlings under B and R/B6 treatments were 2.8 times and 1.1 times higher than that of control, respectively. Pumpkin seedlings treated with R/B1 and R/B6 had 110% times and 34% higher PI_abs, respectively, than control seedlings. In summary, alternating irradiation of watermelon and pumpkin seedlings with red and blue light effectively improved the growth and development of watermelon and pumpkin seedlings and enhanced the chlorophyll fluorescence performance, while blue light can increased the crude protein content and red light can increase the crude polysaccharide content. Thus, when watermelon and pumpkin seedlings are cultured in a uniform manner, alternating red and blue light can maximize the seedling quality and provide high-quality seedlings for factory production.

Key words: Plant factory, Growth and development, Chlorophyll, Good quality seedling