Microclimate, Canopy Structure and Photosynthesis in Canopies of Three Contrasting Temperate Forage Grasses: I. Canopy Structure and Growth

Abstract

The crop growth rates and structures of three temperate forage grasses Lolium perenne cv. S24, L. perenne cv. Reveille and Festuca arundinacea cv. S170, were examined in the field during a summer growth period. The growth rates of the varieties were remarkably similar at 7 g DM m⁻² day⁻¹. The angular structures of the varieties were different and they varied during the experiment. However, these differences did not seem to affect crop growth rates. Nevertheless, a decrease in the efficiency of light energy conversion of approximately 24 per cent was observed after a change to a more prostrate form of canopy due to lodging. There appeared to be an inverse relationship between the number of tillers per unit ground area and the weight of an individual stem. There were large numbers of relatively light tillers in S24 whereas S1 70 had fewer but heavier tillers. Furthermore, S24 had many small leaves per unit ground area compared with SI70 which had fewer longer leaves per ground area and a slower rate of leaf appearance. There were diurnal changes in the rates of leaf extension for all the varieties. The mean daily extension rates declined as the canopies developed.