Growth retardation and photosynthetic responses of Watermelon plug seedlings exposed to wind stimulation

Plants subjected to mechanical stimulation respond by undergoing morphological changes (thigmomorphogenesis). Wind is an environmental factor that induces mechanical stimulation of plants, affecting their growth and photosynthetic responses depending on its speed. In this study, we evaluated the effects of wind stimulation on watermelon seedlings in terms of wind speed, stimulation time, and application timing. We found that wind stimulation decreases the growth of watermelon seedlings, mainly suppressing their height. Among different wind treatments, the dwarf rate was the highest in the treatment performed at a wind speed of 4 m‧s −1 for 10 h per day. Compactness was the highest in the control treatment with diniconazole, and it increased with increasing exposure to different wind treatments. Low wind speeds, such as 1 m‧s −1 , increased the photosynthesis rate and water-use efficiency of the exposed seedlings; however, wind speed of 4 m‧s −1 decreased the photosynthesis rate. Moreover, wind stimulation increased transpiration in watermelon seedlings. Among different plug seedling production stages, wind application after the grafting stage resulted in effective growth retardation of watermelon seedlings. After transplanting, wind stimulation at the plug seedling stage did not have a negative effect on watermelon growth. Thus, wind stimulation can be used as a potential growth retardant for suppressing plant height in watermelon seedlings.