The pasture ryegrass plant, what is it?

Abstract

Detailed studies of plant growth processes are important in understanding the performance and persistence of species in pastures, particularly in response to uncharacteristic environmental stress. The morphology of perennial ryegrass plants in mixed sheep grazed pastures was determined in self contained farmlets undercontrasting managements of rotational grazing, set stocking or a combination of both. Average size was 90 mg total DW, with 4- 5 tillers and 12-13 leaves, little different to white clover. Ryegrass exhibits strong clonal growth, with extension at the apex and death of the basal stem releasing branches to form new plants at regular intervals, maintaining a stable population structure of small plants all year. The normally short internodes on ryegrass stems can elongate to form stolon and elevate the apex to a more favourable position if survival is threatened. On average only 2530% of plants contained stolon at any one time. Because of high plant density the quantities of ryegrass stem present was often in excess of that produced by white clover in the same swards. Grazing management did not affect plant structure (numbers of tillers, leaves etc) only their size (dry weight), but had marked effects on pasture structure and subsequent survival of plants under stress. Keywords perennial ryegrass, plant morphology, grazing management, seasonal variation, plant survival, stolon formation