[OBJECT]To provide an agricultural chemical and the like with the use of an effect of inducing systemic acquired resistance in a plant. To provide a growth inhibitor of not only a plant pathogenic bacterium but also a harmful microorganism.[MEANS FOR RESOLUTION]Utilization of a rare sugar for inducing systemic acquired resistance in a plant or inhibiting the growth of a microorganism. Utilization thereof as an agricultural chemical with the use of the effect of inducing systemic acquired resistance in a plant, a plant disease inhibitor, an inducer of a plant growth regulatory factor (i.e., an inducer of plant hormone-like actions consisting of disease resistance, insect resistance, fruit maturation, breaking of dormancy, regulation of germination, drying resistance, and other than this, resistance to environmental stresses such as low temperature resistance, high temperature resistance, salt resistance and heavy metal resistance and promotion of flowering) and a microorganism growth inhibitor. The rare sugar is an aldose (D-allose, D-altrose or L-galactose) or a ketose (D-psicose or a mixture of D-psicose and D-fructose).
