MORPHOLOGICAL RESPONSES TO NUTRIENT AVAILABILITY IN 4 CLONAL HERBS

This paper examines morphological plasticity of clonal plants of contr asting habitats and of contrasting architectures in response to nutrie nt supply. The hypotheses were tested that plants from rich habitats p ossess greater plasticity in response to variation in resource supply than species from poor habitats, and that rhizomatous species are less plastic in their response than stoloniferous species. Two sympodial r hizomatous herbs (Carex flacca, C. hirta) and two monopodial stolonife rous herbs (Trifolium fragiferum, I: repens) were subjected to four le vels of nutrient supply in a garden experiment. One of the two species of each genus (C. hirta, T. repens) is from fertile and the other fro m infertile habitats. We measured 1) whole plant characters: total pla nt dry weight, number of modules (product of a single apical meristem) and number of ramets; 2) ramet characters: ramet leaf area and ramet height; and 3) spacer characters: branches per module, length per modu le and length per module internode. All measured characters in the Tri folium species significantly responded to treatment: the values for al l measured characters increased with higher levels of fertilization. T he differences in plant characters between fertilization levels were l arger in Trifolium repens than in T. fragiferum in terms of whole plan t characters, ramet characters and stolen internode length. The two Ca rer species did not differ in their responses to treatment in terms of most characters measured. In ramet characters and in some whole plant characters the species from fertile habitats were more plastic than t hose from infertile habitats. In spacer characters this pattern was no t found. Foraging could not be demonstrated unequivocally. Morphologic al plasticity in the stoloniferous (Trifolium) species was much larger than in the rhizomatous (Carer) species. This seems in accordance wit h a foremost storage function of rhizomes, as against a foremost explo rative function of stolons.