Abscisic acid has many physiological functions, such as inducing plant dormancy, inhibiting seed germination and plant growth, and stimulating stomatal closure. Abscisic acid is one of the important factors leading to dwarfing of infected plants. The abscisic acid content of tobacco mosaic disease, cucumber mosaic disease, tomato verticillium wilt and other diseases is higher than the normal level, showing different degrees of dwarfing.