Comparison of early development of three grasses: Lolium perenne, Agrostis stolonifera and Poa pratensis

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anglais. Background and Aims To improve the management of grass communities, early plant development was compared in three species with contrasting growth forms, a caespitose ( Lolium perenne), a rhizomatous (Poa pratensis) and a caespitose-stoloniferous species (Agrostis stolonifera). Methods Isolated seedlings were grown in a glasshouse without trophic constraints for 37 d (761 degrees Cd). The appearance of leaves and their location on tillers were recorded. Leaf appearance rate ( LAR) on the tillers and site-filling were calculated. Tillering was modelled based on the assumption that tiller number increases with the number of leaves produced on the seedling main stem. Above- and below- ground parts were harvested to compare biomass. Key Results Lolium perenne and A. stolonifera expressed similar bunch-type developments. However, root biomass was approx. 30% lower in A. stolonifera than in L. perenne. Poa pratensis was rhizomatous. Nevertheless, the ratio of above-ground : below- ground biomass of P. pratensis was similar to that of L. perenne. LAR was approximately equal to 0.30 leaf d(-1) in L. perenne, and on the main stem and first primary tillers of A. stolonifera. LAR on the other tillers of A. stolonifera was 30% higher than on L. perenne. For P. pratensis, LAR was 30% lower than on L. perenne, but the interval between the appearance of two successive shoots from rhizomes was 30% higher than the interval between two successive leaf stages on the main stem. Above- ground parts of P. pratensis first grew slower than in the other species to the benefit of the rhizomes, whose development enhanced tiller production. Conclusions Lolium perenne had the fastest tiller production at the earliest stages of seedling development. Agrostis stolonifera and P. pratensis compensated almost completely for the delay due to higher LAR on tillers or ramets compared with L. perenne. This study provides a basis for modelling plant development