EXPANSION OF POTATO CELLS IN RESPONSE TO JASMONIC ACID

Since jasmonic acid (JA) has strong potato tuber-inducing activity and tuberization of potato plants is initiated mainly by expansion of cells, it is highly likely that JA is capable of inducing expansion of potato cells. When disks cut from potato tubers were cultured on medium that contained JA, the disks began to swell markedly after 1 day in culture. Within 5 days in culture, the fresh weight of the disks doubled in the presence of JA at 3 x 10(-5) M. Light microscopy revealed that the swelling was due to the expansion and not the division of cells. JA exhibited this expansion-inducing activity at concentrations above 10(-5) M. Air-borne methyl jasmonate (JA-Me) also exhibited this activity. The cells that expanded in response to JA in the medium or to airborne JA-Me were localized on the lower side of each disk. The localization seemed to be a result of the greater availability of water. Sucrose in the culture medium was not necessary for the expansion of cells. The expansion-inducing activity appeared to be specific to JA and related compounds, since various plant hormones and a precursor of ethylene had no appreciable effects on the size of cells. Abscisic acid at concentrations above 10(-5) M and benzyl adenine at concentrations above 10(-4) M markedly inhibited the JA-induced expansion of cells. The expansion-inducing activities of JA and JA-Me seem to be associated with their tuber-inducing activities.