GENOTYPIC VARIATION AND PLASTICITY OF CLONAL GROWTH IN RELATION TO NUTRIENT AVAILABILITY IN AMPHIBROMUS-SCABRIVALVIS

1 Genotypic variation and plasticity of clonal growth and storage in relation to nutrient availability were examined in 10 clones of a perennial, corm-forming grass (Amphibromus scabrivalvis). The clones (derived from seeds) were each separated into 72 ramets and planted in a glasshouse. Half of all ramets received fertilizer every 2 weeks, while the others received only water. 2 At 11, 20 and 26 weeks, 24 ramets per clone genotype were harvested; number of ramets and corms, and corm, rhizome, root, and shoot dry mass were recorded. Ramet number and rhizome mass were indicators of clonal growth, while corm number and mass were indicators of storage. 3 There were highly significant differences among clones for all traits examined at all ages. The response to nutrient addition showed genotypic variation, but depended on age for at least some traits. 4 Substantial phenotypic plasticity of traits important to clonal growth and storage was exhibited by the clones in response to nutrient availability. Norms of reaction for number of ramets and corms varied with clone and age, indicating the potential for microevolutionary responses to soil nutrient heterogeneity in this population. 5 Phenotypic plasticity increased with plant age; corm and shoot mass were most responsive to nutrient addition, but variation in response among clones was relatively low for these traits. 6 Rhizome mass showed the most variation in plasticity from clone to clone at all plant ages, suggesting that foraging capability could respond to selection pressures such as spatially heterogeneous soil nutrients in this population.