Competition studies in diploid and tetraploid varieties of Lolium perenne: 1. The influence of density and proportion of sowing

Abstract

Two varieties of Lolium perenne, the diploid Hora and the tetraploid Terhoy were sown either as a pure stand or as a binary mixture on to the surface of multipots filled with a standard John Innes compost. Density of sowing was varied over the range of 16, 24, 36, 50 and 100 seeds/pot. There were four replicates. The pattern of germination was followed over a period of 14 days when it was found that (i) the varieties did not differ in their germination when grown alone, but in mixtures the diploid was slower to germinate than the tetraploid, (ii) as the density of sowing per pot was increased, the mean germination time (MGT) was increased, and (iii) the final germination of both verities decreased with increasing density.In a second experiment the same procedures were followed as before but seed of each variety was sown either as a pure stand or in a mixture of varying proportion as follows: 100:0, 75:25, 50:50, 25:75, 0:100.The results showed that (i) the diploid had the fastest MGT whilst the mixture values showed no significant variation, and (ii) the final germination percentage of the diploid decreased relative to its pure stand value as its proportion in mixtures decreased, whilst the tetraploid under the same circumstances increased relative to its pure stand value.It is suggested that differences such as those found could be explained by the presence of germination inhibitors in the seed coats of the two ryegrass varieties. Boe^-B

Meadow Fescue and Tetraploid Perennial Ryegrass—Two New Species for Overseeding Dormant Bermudagrass Turf

“…There were no significant differences in seedling vigor between diploid, tetraploid, or intermediate ryegrass at any location (Table 1). Earlier work on germination and seedling vigor of tetraploid ryegrasses has been inconclusive, with some studies showing improved vigor of tetraploids due to increased seed size (Norrington‐Davies and Harries, 1977). However, recent studies by Sanderson and Elwinger, 2004, found no relationship between increased seed size in tetraploid and increased seedling vigor, which concurs with the present study (Table 1).…”

Evaluation of New Herbage Cultivars

“…It appears that the growth of grasses as pure swards under cutting can be used to predict quite well their performance in a mixture of other grasses (Harris and Sedcole, 1974)) but of course this does not take into account factors like inhibition of germination by seed of one cultivar on another as shown by Norrington- Davies and Harries (1977)) or the possibility of selective grazing when animals are present. In the case of white clover, correlations between growth in monoculture and in mixtures have often been low, although correlations between the best lines in monoculture and mixtures were higher for the better lines than the poorer lines (Dijkstra and de Vos, 1972).…”