Light intensity and the growth of Eucalyptus seedlings. II. The effect of cuticular waxes on light absorption in leaves of Eucalyptus species

Abstract

In the species of Eucalyptus investigated, differences in reflection characteristics caused by the amount and orientation of waxes on the leaf cuticle resulted in variation in the capability of leaves to absorb light in the waveband 400-700 nm. When the waxes occur as clustered rods or tubes, as in E. pulverulenta and in juvenile and intermediate leaves of E. bicostata, the leaves have a glaucous appearance. The glaucescence is removed when the leaves are wiped with cotton wool. Wiped leaves absorb a greater proportion of incident light than leaves with wax intact and, consequently, have higher rates of apparent photosynthesis at light fluxes below those required for light-saturated photosynthesis. The optical characteristics of leaves of seedlings of E. fastigata and E. bicostata are not measurably affected when the intensity of the light climate in which they are growing is varied, but the temperature of the environment affects the reflectance of glaucous juvenile leaves of E. bicostata.