MORPHOLOGICAL PLASTICITY IN TRIFOLIUM-REPENS L - THE EFFECTS OF CLONEGENOTYPE, SOIL NUTRIENT LEVEL, AND THE GENOTYPE OF CONSPECIFIC NEIGHBORS

This study investigates the effects on clone morphology when different genotypes of Trifolium repens L. (white clover) are grown together in mixtures. Three genets of T. repens were selected from a field popula tion and grown in a greenhouse partly in isolation and partly in mixtu re with another T. repens clone, either of the same or of a different genotype, and at two soil nutrient levels. Responses in growth and for m were assessed by measuring the following variables: dry mass per qua drat, polygon area, ramet mass, number of nodes, proportion of nodes b ranching and internode length. Analysis revealed numerous significant main effects of soil nutrient level, as well as identity of own and of neighbour genotype on clone growth and form but did not detect any in teractions; this may have been due to the low number of surviving repl icates. In response to increasing soil nutrient levels there was (i) a n increase in number or size of some of the characters measured and (i i), a change in form of the plant, which affected the placement of dau ghter ramets. In general, the response of most variables to increased soil nutrients was consistent with the hypothesis that clones consolid ate occupation of favourable habitat patches and increase their probab ility of escape from unfavourable conditions. Clover clones also respo nded to neighbouring clones in a manner consistent with this hypothesi s, increasing the likelihood of growing away from competitors, althoug h the responses were not as pronounced as those induced by soil nutrie nts. The responses were strongest in fertilized conditions and in the clone with the most guerilla-like growth form. The precise response ex hibited by any clone differed according to the genotype of the neighbo ur encountered. The changes provoked by conspecific neighbours were lo calized within the parts of the clones encountering the neighbours, ra ther than spread throughout the whole clone.