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

Abstract

Profiles of shortwave radiation, net radiation and temperature were measured in swards of three grasses of contrasting structure Lolium perenne cv. S24, L. perenne cv. Reveille and Festuca arundinacea cv. S170. Measurements were also made of the reflection of shortwave radiation, leaf water potential and stomatal resistance. Differences in canopy structure influenced the absorption and reflection of radiation by the varieties. The absorption of net radiation and its influence on air temperature inside the canopy was shown to vary with canopy structure. Calculations showed that diurnal changes in the reflection and transmission of light (400–700 nm) would have little effect on canopy photosynthesis. No clear relationship between leaf extension rate, temperature and leaf water potential could be established, although decreases in water potential did appear to reduce the potential response of leaf extension rate to temperature.