Are Mistletoes Shade Plants?
Mistletoes usually have slower rates of photosynthesis than their hosts. This study examines CO2assimilation, chlorophyll fluorescence and the chlorophyll content of temperate host parasite pairs (nine hosts parasitized by Ileostylus micranthus and Carpodetus serratus parasitized by Tupeia antarctica). The hosts of I. micranthus had higher mean annual CO2assimilation (3.59 ± 0.41 µmol m-2 s-1) than I. micranthus(2.42 ± 0.20 µmol m-2 s-1), and C. serratus(2.41 ± 0.43 µmol m-2 s-1) showed higher CO2assimilation than T. antarctica(0.67 ± 0.64 µmol m-2 s-1). Hosts saturated at significantly higher electron transport rates (ETR) and light levels than mistletoes. The positive relationship between CO2assimilation and electron transport suggests that the lower CO2assimilation rates in mistletoes are a consequence of lower electron transport rates. When photosynthetic rates, ETR and chlorophyll a /b ratios were adjusted for photosynthetically active radiation, hosts did not have significantly h
