HEMIPARASITIC NUTRITION IN ANGIOSPERMS

Abstract

The structure of the root haustorium and the hairs of the shoot of Odontites has been examined by light microscopy. The haustorium provides a direct xylem‐xylem link between root of host and hemiparasite. Tracer studies show that solutes move across this pathway from the host to the shoot of the hemiparasite. Three types of hair clothe the shoot. They develop precociously, commencing to function in guttation before the stomata are perforated and the vascular tissues are differentiated. Guttation fluid and bleeding sap of members of associations of Odontites with barley or Stellaria media were analysed for phosphate, nitrate, calcium, potassium, amides and amino acids. The results suggest that the shoots of the hemiparasite and its host can absorb selectively the solutes supplied from their roots. Microautoradiographic studies of the distribution of [ 3 H]leucine fed to shoots of Odontites through the xylem show that cells bordering on the transpiration pathway actively assimilate the radiosubstrate. Mesophyll cells and glandular hairs of the leaf are particularly active in this respect. It is suggested that glandular secretion plays a relatively important role in directing solutes mto young parts of the shoot.