Great Basin Naturalist


Ultrastructure of the chloroplasts of white rubber rabbitbrush (Chrysothamnus nauseosus (Pallas) Britt. ssp. albicaulis) was observed with electron microscopy. In addition, leaf anatomy was observed with light microscopy. Previously, it had been reported that the leaves of this desert shrub exhibited a relatively high rate of photosynthesis when compared to other C3 plants. Comparisons with chloroplasts of other C3 and C4 plants demonstrated a reduced amount of granal stacking in the rabbitbrush. However, the classification of rabbitbrush as a C3 plant is confirmed. RUBP-carboxylase concentration is reported at about 450 mg · ml-1 stromal space based on the estimation of 1 mg of chlorophyll per 25 ul of stromal space in a normal C3 chloroplast and data from an assay to determine the ratio of RUBP-carboxylase to chlorophyll.