INFLUENCE OF COPPER ON ROOT-GROWTH AND MORPHOLOGY OF PINUS-PINEA L AND PINUS-PINASTER AIT SEEDLINGS

We assessed the effects of Cu on root growth and morphology of stone p ine (Pinus pinea L.) and maritime pine (Pinus pinaster Ait.) seedlings grown in culture solutions supplied with 0.012 (control), 0.1, 1 or 5 mu M CuSO4. The presence of 5 mu M Cu in the nutrient solution comple tely inhibited root growth of both species within 3 days. In both spec ies, taproot elongation was reduced in the presence of 1 mu M CU, alth ough partial growth recovery occurred after 7 days of treatment. The p resence of 0.1 mu M Cu in the culture solution slightly enhanced root elongation in P. pinnster, but did not significantly influence root el ongation in P. pinea. In both species, root weight per unit length inc reased in response to Cu exposure, and in P. pinaster, root diameter w as significantly increased. The Cu treatments also affected lateral ro ot number and length. In the presence of 1 mu M Cu, both species forme d only short lateral primordia. The 1 mu M Cu treatment increased the lateral root index (number of roots per cm of root length) of P. pinas ter, but decreased that of P. pinea, compared with control values. Nei ther the 0.1 nor 1 mu M Cu treatment had a significant effect on the m itotic index of either species. We conclude that cell elongation is mo re sensitive to Cu than cell division. Cell membrane damage, as indica ted by Trypan blue staining, occurred after 10 days of exposure to 1 m u M Cu.