Growth and Quality of Grafted Watermelon Seedlings Under Controlled Light Intensity in a Plant Factory Nursery System

This study was conducted to evaluate the growth and quality of grafted watermelon seedlings under different controlled light intensities in a plant factory nursery system.The watermelon scion cultivars were used 'BravoKkul (BK)' for the high-temperature season and 'SantaKkul (SK)' for the low-temperature season.For rootstocks, 'BullojangSaeng (BS)' was used for the high-temperature season and 'DongjangGun (DG)' for the low-temperature season.Light intensity treatments were applied 125 25, 225 25, and 325 25 molm -2 s -1 .The highest plant height was observed at 125 25 molm -2 s -1 for the high-temperature season grafted seedlings (BK+BS) and at 225 25 molm -2 s -1 for the lowtemperature season grafted seedlings (SK+DG).Both BK+BS and SK+DG seedlings showed the largest stem diameter and highest number of nodes at 225 25 molm -2 s -1 .Root length and leaf area were greatest at 325 25 molm -2 s -1 for BK+BS and at 225 25 molm -2 s -1 for SK+DG.Shoot and root fresh and dry weights were highest at 225 25 molm -2 s -1 during both high-and low-temperature seasons.The compactness of seedlings increased with higher light intensities in both cultivars, particularly noticeable in BK+BS.Leaf area ratio (LAR) significantly increased with increasing light intensity in BK+BS but showed no significant difference in SK+DG.Overall, the growth characteristics were optimal at 225 25 molm -2 s -1 , although considering seedling quality, more robust seedlings were produced at 325 25 molm -2 s -1 .