A POSSIBLE ROLE FOR JASMONIC ACID IN ADAPTATION OF BARLEY SEEDLINGS TO SALINITY STRESS

The changes caused by NaCl salinity and jasmonic acid (JA) treatment ( 8 days) on growth and photosynthesis of barley plants (Hordeum vulgare L., var. Alfa) have been studied. Gas exchange measurements and analy sis of enzyme activities were used to study the reactions of photosynt hesis to salinity and JA. Both 100 mM NaCl and 25 mu M JA treatment le d to a noticeable decrease in both the initial slope of the curves rep resenting net photosynthetic rate vs intercellular CO2 concentration a nd the maximal rate of photosynthesis, The calculated values of the in tercellular CO2 concentration, CO2 compensation point, and maximal car boxylating efficiency of ribulose-1,5-bisphosphate carboxylase support the suggestion that biochemical factors are involved in the response of photosynthesis to JA and salinity stress. The activities of phospho enolpyruvate carboxylase and carbonic anhydrase increased more than tw ofold. Pretreatment with JA for 4 days before salinization diminished the inhibitory effect of high salt concentration on the growth and pho tosynthesis, The results are discussed in terms of a possible role of JA in increasing salinity tolerance of the barley plants.