WATER RELATIONS, GAS-EXCHANGE AND GROWTH OF DOMINANT AND SUPPRESSED SHOOTS OF ARBUTUS-UNEDO L

Basal shoots produced by Arbutus unedo L. after cutting at ground leve l vary in size and growth rate, and are classified accordingly as domi nant or suppressed. The suppressed shoots eventually cease growth and die. In this study, we investigated the role of light and water in the competition among shoots of A. unedo. Dominant and suppressed shoots of A. unedo showed similar leaf water potentials and tissue water rela tions over the year, suggesting that water status is not responsible f or the lack of flushing in suppressed shoots. Although suppressed shoo ts did not flush under low light, they showed many characteristics of shade-tolerant plants. Leaves of suppressed shoots had lower leaf cond uctance and light-saturated photosynthetic rate, and higher specific l eaf area than leaves of dominant shoots. We conclude that light was th e main resource determining competition among shoots and the death of suppressed shoots.