Implicated in the defense of plants against pathogens. Hydrolysis of (1->3)-beta-D-glucosidic linkages in (1->3)-beta-D-glucans. Is expressed primarily in epidermal cell of healthy plant, and following induction by ethylene, accumulates in mesophyll cells. By ethylene and salicylic acid. Belongs to the glycosyl hydrolase 17 family.