Alleviation of salinity stress in broccoli using foliar urea or methyl-jasmonate: analysis of growth, gas exchange, and isotope composition

We studied the effects of foliar application of urea or methyl-jasmonate (MeJA) on the salinity tolerance of broccoli plants (Brassisca oleracea L. var. italica). Plant dry weight, leaf CO2 assimilation, and root respiration were reduced significantly under moderate saline stress (40 mM NaCl) but application of either urea or MeJA maintained growth, gas exchange parameters, and leaf N-NO3 (-) concentrations at values similar to those of non-salinized plants. Additionally, when these two foliar treatments were applied leaf Na+ concentration was reduced compared with control plants grown at 40 mM NaCl. However, at a higher salt concentration (120 mM NaCl), no effect of the foliar applications was found on these parameters. Salinity also decreased leaf delta N-15 but increased delta C-13. Our study shows the feasibility of using foliar urea or MeJA to improve tolerance under moderate saline stress.