PLASTICITY IN MORPHOLOGY AND BIOMASS ALLOCATION IN CYNODON-DACTYLON, A GRASS SPECIES FORMING STOLONS AND RHIZOMES

Stolons and rhizomes may be important for the placement of leaves and roots in new microhabitats (foraging), as well as for the storage of r esources. In a species which forms both types of structures, such as C ynodon dactylon, both such functions could be combined in a single str ucture, or rhizomes and stolons could exert different functions. We ex amine these functions in C. dactylon, by investigating plasticity in m orphology and biomass allocation in response to variation in light and nutrient availability. Both stolon and rhizome branching intensities were reduced in response to lower light and lower nutrient levels. Sto lons and their internodes elongated greatly under lower light levels, but slightly shorter under lower nutrient levels. The lengths of rhizo mes and their internodes did not respond significantly to nutrient ava ilability. Only at low light levels did the plant form orthotropic sho ots. Rhizomes failed to develop, and biomass allocation to stolons was slightly lower under low compared to high light intensity. The morpho logy of stolons was more responsive than the morphology of rhizomes to resource supply. Biomass allocation to stolons, however, was less var iable than allocation to rhizomes in response to light and nutrient tr eatments. These results support the contention that stolons enable C. dactylon to forage for light while rhizomes serve as organs for storag e of resources and meristems. These results are interpreted in terms o f the efficiency of exploitation of light patches within the habitat o f C dactylon, and the ability to survive after unpredictable disturban ces.