CO₂ Storage in Eucalyptus Oil Glands; a Hypothesis Disproved

Abstract

CO₂ is known to be highly soluble in oils. The hypothesis investigated was that the contents of leaf oil glands in Eucalyptus spp, might constitute a significant reservoir for CO₂ within the leaf. Solubilities of CO₂ in extracted oil from E. socialis leaves were measured and found to be 3-6 times that of CO₂ in water. The volume of oil glands constitutes up to 12% of the total leaf volume. It is shown that the possible capacity of this reservoir for CO₂ could at most amount to the equivalent of about 35 min of dark respiration, and therefore could not constitute a significant internal reservoir in the dark period. There appears to be a correlation between oil-gland percentage volume and the rainfall where the trees grew. Values are given for the percentage volume of the other tissues of the leaf and for cuticular resistance to CO₂ diffusion.