Turczaninowia (Mar 2017)
Anatomy of the roots of some northern hemiparasites (Orobanchaceae)
Abstract
The root structure and the haustorial formation of 5 northern hemiparasites: Bartsia alpina, Castilleja lapponica, Pedicularis lapponica, Pedicularis sceptrum-carolinum, Rhinanthus minor subsp. groenlandicus (Orobanchaceae) have been studied. The autotroph Scrophularia nodosa (Scrophulariaceae) has been chosen as a control. It is shown that the main preconditions providing the possibility of rapid haustorium development are the long life of the primary outermost tissue of the root – the rhizodermis that covers the entire length of both young and older roots, and constant readiness of this tissue to form special haustorial hairs, and also an unusual structure of exodermis, which in many details is similar to rhizodermis. The formation of haustorial hairs is one of the earliest structural events in haustorium development; the haustorial hairs are long, with a smooth surface. The division and elongation of cells in the outer tissues play a major role in the early stages of endophyte development. The parasitic form of life influence the inner structure of the vascular cylinder that appears as the reduction of phloem conductive elements and the accumulation of large amounts of starch in the xylem. It was found that the haustoria can penetrate not only in the roots but also in the rhizomes of the host plants.
