Meloidogyne incognita-Induced Changes in Cell Permeability of Galled Roots

Electrolyte leakage of Meloidogyne incognita-infected and healthy tomato roots was compared by conductivity measurements, and by compartmental analysis using Rb. Conductivity measurements suggested difference in electrolyte loss from healthy and galled roots. On a percentage basis, a greater rate of efflux occurred for healthy plants, but galled roots contain more electrolytes and may show a larger net loss. Compartmental analysis indicated that: (i) the longer half-time for Rb loss from vacuoles of galled root cells could indicate either a greater vacuolar content or decreased tonoplast permeability, (ii) the shorter half-time for loss Rb from the cytoplasm of galled root cells could reflect either a reduced cytoplasmic content or an increased plasma membrane permeability, and (iii) in split-root plants, the permeability of the tonoplast and the plasma membrane of cells in nongalled roots is increased by nematode infection on the other half of the root system. Thus, a mechanism for mobilizing minerals to the infection site is proposed.