Benefits of clonal propagation: impact of imported assimilates from connected ramets

Abstract

To benefit from expansion in space, a clonal plant must at first invest some of its resources in the production of clonal offspring. When resources are scarce, investment in clonal growth can be costly. Investment could be more costly in the case of long compared to short rhizomes. However, benefits can also be substantial if the plant can attain resources from a large area. Thus, both the growth form and soil fertility can influence the balance between costs and benefits from clonal growth. We established an experiment in which half of the plants of Elymus repens (long rhizomes) and Alopecurus pratensis (short rhizomes) were planted through a black agrotextile sheet laid on either a fertile or an infertile soil. The textile sheet prevented clonal offspring from reaching sunlight. The other half of the plants were allowed to grow freely. The size of the genets and the number of clonal offspring (daughter ramets) were primarily affected by soil fertility while covering only impacted the growth of E. repens. Covering increased the seed production of A. pratensis by almost 50 % while total rhizome length per genet of E. repens was significantly larger in the nutrient-poor soil and in covered conditions. E. repens benefited from clonal growth only in fertile conditions where genets grew bigger, whereas A. pratensis showed no signs of direct benefit. We conclude that it is essential to consider the growth form of genets when evaluating the relationships between clonal growth or reproductive behaviour and environmental conditions.