Abstract

Hydroponic culture has been used to compare copper and cadmium tolerance in fiveSalix species from North Morocco using different approaches. Measurements of growth parameters have been combined with those of some photosynthetic parameters. Tolerance index based either on root or shoot growth allowed to defineSalix pedicelata and Salix purpurea as Cu and Cd-tolerant species, respectively. From the methodological point of view, the use of tolerance index based on aerial part growth, appeared most adequate for the screening of metal tolerance in woody plants. On the other hand, no significant effect on chlorophyll content was observed under treatment with either Cu or Cd, in any of the Salix species analyzed. In vitroexperiments with thylakoid membranes showed that the effects on the electron transport chain differ for each metal and species used. Furthermore, it seems that metal tolerance at the chloroplast level is distinct to that of the whole plant.

Key word: Salix, heavy metals, tolerance index, photosynthesis.

Abbreviation

Chl, chlorophyll; TI, tolerance index; PPBQ, phenyl-p-benzoquinone; PSII, photosystem II.