FREE PROLINE ACCUMULATION IN SAPWOOD, BARK AND LEAVES OF 3 EVERGREEN SCLEROPHYLLS AND A COMPARISON WITH AN EVERGREEN CONIFER

Free proline content was investigated in sapwood, bark and foliage of Ceratonia siliqua, Laurus nobilis, Myrtus communis and Pinus halepensis throughout a 12-month period. Free proline concentration in leaves and needles peaked during the drought and cold periods, respectively, then declined prior to the flushing of the new foliage; the minimum values coincided with the expansion of the young foliage. The results indicate that proline was neither translocated during stress periods, nor accumulated in turgid foliage. In the bark and sapwood of the four species examined, free proline content was generally lower compared with that of the foliage, but the seasonal trends were similar. Thus, free proline accumulation in sapwood and bark decreased during the main and secondary growth periods.