CYTOLOGICAL CHANGES INDUCED BY THE ECTOPARASITIC NEMATODE LONGIDORUS LATOCEPHALUS IN TOBACCO ROOTS

Abstract

The migratory ectoparasitic root nematode Longidorus latocephalus, exposed to tobacco seedlings in aseptic agar culture, fed exclusively on the root tip. The plant response was swelling of the root apices which became transformed into terminal galls three days after nematode infection. Sections through the galls incited by L. latocephalus revealed the presence of a cluster of necrotic cells representing the feeding site. The drastic disturbance of these cells was represented by a general loss in distinctness of the cell membranes and the disappearance of cytoplasmic organelles. Concomitant with this change was the hypertrophy of the cells bordering the feeding area. An increased cytoplasmic density with gelled ground substance and proliferation of whorls of endoplasmic reticulum, producing lipid bodies together with dense osmiophilic inclusions in the vacuoles indicated that nematode elicitors induced an hypersensitive host response. Changes in cell structure were not restricted to cells close to the nematode but also involved, though to a lesser extent, cells away from this region. As a result, the root tip lost its normal physiology and growth efficiency.