Great Basin Naturalist


Basic aspects of photosynthesis were investigated in white rubber rabbitbrush (Chrysothamnus nauseosus (Pallas) Britt. ssp. albicaulis), a common C3 deciduous shrub native to arid regions of the western U.S. Under favorable field conditions, net photosynthesis (Pn) ranged from 36 to 73 mg CO2 · dm −2 · hr−1, which is relatively high for a woody species. The leaves from the actively growing flowering shoots exhibited higher Pn than those on the vegetative shoots. Pn also varied according to the age of the leaves and the location of the plants. Pn did not light saturate even at quantum flux densities (QFD) equivalent to full sunlight. The light compensation point was relatively high (ca 100 μmol · m−2 · S−1), perhaps due to the presence of a tomentose vestiture on the leaf surface. At high QFD's, the stomatal conductance was high (ca 520 mmol · m2 · s−1) for a woody species. RUBP-carboxylase content of the leaves ranged from 20 to 22 mg per gram F.W., which is similar to that found in most C3 crop species. These results suggest that rabbitbrush is able to maintain high rates of Pn, at least under nonstressed conditions.