OCCURRENCE AND IDENTIFICATION OF JASMONIC ACID AND ITS AMINO-ACID CONJUGATES INDUCED BY OSMOTIC-STRESS IN BARLEY LEAF TISSUE

The effect of osmotically active substances on the alteration of endog enous jasmonates was studied in barley (Hordeum vulgare L. cv. Salome) leaf tissue. Leaf segments were subjected to solutions of D-sorbitol, D-mannitol, polyethylene glycol 6000, sodium chloride, or water as a control. Alterations of endogenous jasmonates were monitored qualitati vely and quantitatively using immunoassays. The structures of jasmonat es isolated were determined on the basis of authentic substances by ca pillary gas chromatography-mass spectrometry. The stereochemistry of t he conjugates was confirmed by high performance liquid chromatography with diastereoisomeric references. In barley leaves,jasmonic acid and its amino acid conjugates, for example, with valine, leucine, and isol eucine, are naturally occurring jasmonates. In untreated leaf segments , only low levels of these native jasmonates were found. After treatme nt of the leaf tissues with sorbitol, mannitol, as well as with polyet hylene glycol, an increase of both jasmonic acid and its conjugates co uld be observed, depending on the stress conditions used. In contrast, salt stress was without any stimulating effect on the levels of endog enous jasmonates. From barley leaf segments exposed to sorbitol (1 M) for 24 h, jasmonic acid was identified as the major accumulating compo und. Jasmonic acid-amino acid conjugates increased likewise upon stres s treatment.