EFFECT OF OVERALL GROWTH-POTENTIAL LIMITA TION ON SOME ARCHITECTURAL TRAITS OF GERANIUM ROSAT (PELARGONIUM SP)

The present study investigates the relation between the vigour (ie., r oughly speaking, the growth potential) and the architecture. The prece dence between branches of different orders of geranium rosat (a woody species of Pelargonium) are investigated by artificially restricting t he overall growth potential of the plant. Such restrictions are achiev ed by planting in pots of different sizes at two different altitudes ( determining contrasted climatic conditions). The main axis (I) reveals absolute priority over all other axes while second order axes (II) sh ow relative priority over third order axes (III). The overall under-de velopment attained by restricting pot volume is not therefore, a mere reduction in scale since speed ratios between axes of different order are modified : architecture adapts to growth potential. The effects of climatic conditions are more ambiguous. Reduction in temperature enta ils an (apparently) homothetical reduction in the elementary rate of l eaf production but is also associated to an increase in branching of s econd order axes which counteracts the former effect.