EFFECTS OF RESOURCE AVAILABILITY ON INTEGRATION AND CLONAL GROWTH IN MAIANTHEMUM-BIFOLIUM

The aim of this study was to investigate whether resource availability affects the degree of physiological integration and the growth patter n of interconnected ramets in the clonal plant Maianthemum bifolium (L .) F.W. SCHMIDT (Liliaceae), a rhizomatous herb of European forests, b y studying it at two contrasting South Swedish beech forest sites term ed ''poor'' and ''rich''. The degree of physiological integration was studied by tracing the pattern of C-14 translocation and in a cutting experiment involving rhizome severing and defoliation treatments. The size of the plants, growth of new rhizomes, branching frequency, dista nce between shoots and the intermode length were compared. The plants were larger, rhizomes had greater specific mass (mg mm-1), intermodes were shorter and branching frequency higher at the rich site. The cutt ing treatments reduced the growth of new rhizomes at both sites, and n ew rhizome segments had lower specific mass in treated plants than in controls, showing the importance of physiological integration for new growth. Translocation of C-14 in May showed that the young rhizome tip was a strong sink for carbon. Basipetal translocation to older portio ns of the rhizome system was greater at the rich site than at the poor site. In September, four months after labelling, the rhizome tips wer e still strongly labelled with C-14 and basipetal translocation had in creased at both sites. Plants at the rich site appeared to translocate larger amounts of C-14 basipetally than plants at the poor site. It i s concluded that M. bifolium shows a plastic response to resource avai lability by varying rhizome growth and branching frequency, but the de gree of physiological integration is probably only indirectly affected through an increased number of sinks (new rhizome branches) along the ramet system at the rich site.