TILLERING PATTERNS IN TURFGRASS SPECIES WITH DISTINCT CLONAL TACTICS

The morphological organisation of the aerial system was compared in three turfgrass species with similar ecological requirements known to exhibit different clonal tactics: the caespitose perennial ryegrass (Lolium perenne L.), the caespitose-stoloniferous creeping bentgrass (Agrostis stolonifera L.) and the rhizomatous Smooth-stalked meadow-grass (Poa pratensis L.). Isolated plants were studied in a greenhouse in semi-controlled conditions with increasing photoperiod and without constraint, perturbation or competition. The number and the emergence of new leaves, tillers, stolons and rhizomes were regularly counted in relation to thermic time over a period of five weeks. The results indicated that, (i) the slowest development of the aerial system in Smooth-stalked meadow-grass and (ii) the fastest one in creeping bentgrass which produced more leaves per tiller than the other species. For all species, primary tillers appeared slower than other tillers. In Smooth-stalked meadow-grass, tillers from rhizome appeared faster than primary tillers from the main shoot. Theoretical growth curves of tiller populations were calculated for each species as a function of thermic time (x, degree-days): A. stolonifera y = 0.6230 e ^0.0055x ; L. perenne y = 0.5528 e ^0.0041x; P. pratensis y = 0.5627 e ^0.003x . These data were used to (i) to calculate the mean rate of leaf emergence from tillers of different orders, and (ii) to build tillering patterns based on the result that total number of tillers increased exponentially with the number of leaves produced by the main shoot.