UPTAKE OF JASMONIC ACID AND RELATED-COMPOUNDS BY MESOPHYLL PROTOPLASTS OF THE BARLEY LEAF

Jasmonic acid (JA) permeates the plasma membrane of mesophyll cells by diffusion as the lipophilic undissociated JAH molecule probably witho ut the participation of a saturable uptake component. The mesophyll pl asma membrane is nearly impermeable to the JA anion. The permeability coefficients of JA and several JA derivatives (its methy ester (JAMe), 7-iso-cucurbic acid (7-iso-CA), 6-epi-7-iso-cucurbic acid (6-epi-7-is o-CA), and both stereoisomers of the JA leucine conjugate ((+)-JA-Leu and (-)-JA-Leu)) were determined and used in a simplified mathematical model to predict stress-dependent JA redistribution between cytosol a nd apoplast in comparison with ABA. The redistribution of JA takes pla ce similar to ABA; however, its velocity is much higher because of the high JA membrane permeability. When the permeability coefficients for the mesophyll plasma membrane are plotted double-logarithmically agai nst the ratio of the distribution coefficient and the molecular ratio to the power of 1.5 (K(D)M(r)(-15)), two straight lines result for two different classes of compounds. The permeability coefficients of JA c onjugates are lower than that of the free acid by approximately one or der of magnitude, but they are still significantly higher than that of ABA.