Virtual Museum of Canada
Jardin botanique de Montréal 
Centre for Forest Research

Being stingy with resources

Some leaves have made changes as they evolved in order to conserve resources. The blade of these leaves, for instance, has completely disappeared: only the petiole remains, and over time it has expanded into a phyllode (An expanded leaf-like petiole taking on the function of a leaf blade.
. The leaf is the tree's biggest user of water; by eliminating the blade and retaining only the petiole, the tree minimizes its water losses. This adaptation is especially valuable in trees that grow in arid climates – when every drop of water counts, transpiration must be carefully controlled.

Photo of phyllodes of a Prickly Moses (Acacia verticillata subsp. ruscifolia)
Acacia verticillata subsp. ruscifolia
© Tony Rodd
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