Uptake of 14C photosynthates from Pisum sativum by haustoria of Erysiphe pisi

TLDR: The technique for isolating haustorial complexes from leaves of Pisum sativum infected with Erysiphe pisi has been used to investigate the nutritional physiology of the host-parasite interface to discuss the role of the haustorium in nutrient transfer from the host to parasite.

Abstract: The technique for isolating haustorial complexes from leaves of Pisum sativum infected with Erysiphe pisi has been used to investigate the nutritional physiology of the host-parasite interface. The numerical efficiency of the extraction procedure was 4 to 5%. The haustorial complexes showed oxygen uptake in vitro which was unaffected by exogenous glucose, sucrose or mannitol. Haustorial complexes were isolated from leaves exposed to [14C]O2 where the mycelium was either left attached or separated from the leaves prior to the exposure. In each case, 14C assimilates soluble in boiling 95% ethanol were found in the haustorial complexes even after they were treated with Triton X-100 (1%). When the mycelium was attached large quantities of soluble and insoluble label accumulated in it. In isolations from leaves where the mycelium had been separated prior to 1 to 12 h exposures the quantity of soluble 14C assimilates in the haustorial complexes increased linearly. Subsequent in vitro incubation for 6 to 12 h had little effect on the amount of soluble label in the complexes, but [14C]O2 was released indicating that assimilates had passed across the host interface into the haustorial cytoplasm. Controls using uninfected leaves and infected leaves exposed in the dark showed that the contribution of host contamination and [14Q]O2 02 fixation by the haustorium was small. The quantity of label resident in the haustorial complexes was only a small proportion of label found in the mycelial and host fractions within the same area of leaf. These results are discussed in relation to the role of the haustorium in nutrient transfer from the host to parasite.