Characterization of a glabrate Encelia farinosa mutant: morphology, ecophysiology, and field observations.

An individual Encelia farinosa (Asteraceae) from Death Valley, California is described that is completely lacking in the dense leaf pubescence covering characteristic of the species. While leaf absorptances to solar radiation of the mutant E. farinosa are much greater than those of the wild type, other morphological aspects and photosynthetic characteristics appear to be similar to those typical for E. farinosa. Leaf temperatures of mutant and wild type E. farinosa in the field are similar, but only because of steeper leaf angles and higher leaf conductances to water vapor in the mutant form. As a consequence of a greater water expenditure for transpirational cooling, the mutant E. farinosa becomes deciduous much earlier in the drought period than do the normal pubescent leaved E. farinosa.