Effects of Seedling Age on the Growth and Physiological Characteristics of Grafted Watermelon Seedlings

To find out the optimal transplanting stage for root pruning hole insertion grafted watermelon seedlings, the growth and physiological changes of grafted seedlings under different physiological ages were investigated. The results showed that the optimum transplanting stage for the grafted watermelon seedlings is the second or the third true leave of watermelon seedlings is fully expanded, about 21-24 days after grafting, at this period the seedlings had less space limitation to the root size. As the seedling age was older than three true leaves, the seedlings would grow excessively, resulting in lower leaves yellowed, weakened mineral absorption capacity of root.