Scanning electron microscopy in nematode-induced giant transfer cells.

A study of giant cells induced by the root-knot nematode, Meloidogyne incognita, in roots of Impatiens balsamina was made by scanning electron microscopy. The cytoplasmic contents of giant cells were removed by a procedure based on KOH digestion, to reveal inner wall structure. Wall ingrowths typical of transfer cells are present in giant cells from six days onwards after induction. They develop on walls adjacent to vascular tissues, and their distribution and development was examined. Pit fields contianing plasmodesmata become elaborated in walls between giant cells, but pit fields are lost between giant cells and cells outside them. The distribution of plasmodesmata in pit fields suggests that de novo formation of plasmodesmata occurs in walls between giant cells. Various aspects of giant cell formation and function are discussed and wall ingrowth development is compared in giant cells and normal transfer cells.