VIEW ARTICLE

Physiology and Biochemistry

Transport of an Apoplastic Fluorescent Dye to Feeding Sites Induced in Tomato Roots by Meloidogyne incognita. R. Dorhout, Transport Physiology Research Group, University of Utrecht, Botanical Laboratory, Lange Nieuwstraat 106, 3512 PN Utrecht, The Netherlands, Department of Nematology, Agricultural University, Binnenhaven 10, 6709 PD Wageningen, The Netherlands; C. Kollöffel(2), and F. J. Gommers(3). (2)Transport Physiology Research Group, University of Utrecht, Botanical Laboratory, Lange Nieuwstraat 106, 3512 PN Utrecht, The Netherlands; (3)Department of Nematology, Agricultural University, Binnenhaven 10, 6709 PD Wageningen, The Netherlands. Phytopathology 78:1421-1424. Accepted for publication 9 May 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-1421.

The fluorescent dye Tinopal CBS was used to investigate whether there is an apoplastic pathway between the stele and the cortex in tomato roots infected with the root-knot nematode Meloidogyne incognita. The endodermis prevented the uptake of the dye into the stele in uninfected as well as in infected parts of the root. The dye entered the stele only via branch roots. During transport in the xylem vessels, the dye left the xylem at the sites of giant cells and remained inside the stele. In experiments in which the root system was partly submerged in the dye solution, the water suction of the giant cells, together with their associated nematodes, was so strong that, in infected branch roots above the solution, the direction of the water movement in some xylem vessels was reversed. We conclude that at the time of feeding water flows within the stele from the xylem compartment toward the giant cells. There is no mass flow of water and nutrients from the cortex to the stele along the body of the nematode or from the stele to the cortex.