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 analysis of enzyme activities were used to study the reactions of photosynthesis to salinity and JA. Both 100 mM NaCl and 25 M JA treatment led to a noticeable decrease in both the initial slope of the curves representing net photosynthetic rate vs intercellular CO 2 concentration and the maximal rate of photosynthesis. The calculated values of the intercellular CO 2 concentration, CO 2 compensation point, and maximal carboxylating 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 phosphoenolpyruvate carboxylase and carbonic anhydrase increased more than twofold. Pretreatment with JA for 4 days before salinization diminished the inhibitory effect of high salt concentration on the growth and photosynthesis. The results are discussed in terms of a possible role of JA in increasing salinity tolerance of the barley plants.

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This study provides evidence that, in the soluble fraction from buffer-washed pea thylakoids, one form of soluble carbonic anhydrase (CA) is associated with rubisco in a stromal protein complex. On native-PAGE gels, it is present as a protein band with MW approximately 160 kDa. On SDS-PAGE gels, it is resolved as a single 25-kDa polypeptide. Analysis of Western blots developed with polyclonal antibodies to barley rubisco and to soluble pea CA shows that a 160-kDa protein with CA activity is associated with rubisco in a protein complex localized on the outer surface of thylakoid membranes.