Physiological Aspects of Parasitism in Mistletoes (Arceuthobium and Phoradendron). II. The Photosynthetic Capacity of Mistletoe

Abstract

Phoradendron leaves contain a chlorophyll content comparable to that of their hosts. They fix large quantities of CO2 with much of the C being deposited as starch. Translocation of photosynthate from mistletoe shoots to their endophytic systems was noted. There was no appreciable transfer of photosynthate to its host even when the infected branches had no leaves. Aerial shoots of Arceuthobium also contain chlorophyll but at a concentration of only 1/5-1/10 that found in the foliage of the host. C fixed by their aerial shoots never was observed to translocate into their own endophytic system or into the host tissue. C fixed in the shoots of Arceuthobium was concentrated in sucrose and malic acid. The rate of C14O2 fixation in the aerial shoots was too low to be measured by an infrared gas analyzer but could be calculated from C14O2 experiments. Values ranged from 0.024 mg of CO2/g dry weight/hour for shoots of A. americanum to 0.003 mg of CO2/g dry weight/hour for A. campylopodum. Dark fixation was about 1/5 the rate for light fixation.