OCCURRENCE OF HYDROXYLATED JASMONIC ACIDS IN LEAFLETS OF SOLANUM-DEMISSUM PLANTS GROWN UNDER LONG-DAY AND SHORT-DAY CONDITIONS

Under short-day (SD) conditions both 11-OH-jasmonic acid (11-OH-JA) an d a smaller quantity of 12-OH-JA occurred in leaflets of Solanum demis sum Lindl. plants which had formed tubers. This is the first time that 11-OH-JA has been detected as a native substance in higher plants. Un der long-day (LD) conditions no tubers were formed and none of these c ompounds were detectable. A positive correlation was found between the occurrence of 11-OH-JA and 12-OH-JA in leaflets of S. demissum and tu ber formation, but a causal relation has yet to be proved. The (-)-JA content in leaflets was not significantly different under short and lo ng days. Mild stress applied to detached SD and LD leaflets caused a r apid accumulation of JA in these leaflets. Upon this treatment an incr ease in the levels of hydroxylated JAs was detected in SD leaflets onl y. JA was a potent promotor of tuber formation in vitro in S. demissum explants. Lipoxygenase (LOX; EC 1. 13.11.12) is involved in the biosy nthesis of JA. Under SD conditions, application of salicylhydroxamic a cid (SHAM), an inhibitor of LOX activity, to the roots did not prevent tuber formation in vivo. It is suggested that daylength controls the hydroxylation of JA. The enzyme(s), responsible for the hydroxylation of JA, would only be effective under SD conditions.