MULTINUCLEATE GIANT CELL FORMATION IN A PACHYPSYLLA GALL ON CELTIS

D undon , T homas R. (Saint Louis U., Saint Louis, Mo.) Multinucleate giant cell formation in a Pachypsylla gall on Celtis . Amer. Jour. Bot. 49(7): 800–805. Illus. 1962.—Cytological antecedents of the multinucleate giant cell in gall tissue of Pachypsylla mamma on leaves of hackberry, Celtis occidentalis , have been presented. The nymph's stylet punctured the epidermis and terminated in a single mesophyll cell where it remained fixed until a multinucleate giant cell formed there. An intracellular cytoplasmic reaction occurred at the tip of the stylet which was attributable either to the secretory or the sucking activity of the nymph. The walls of cells surrounding the tip of the stylet gradually became less distinct as demonstrated by a decreasing affinity for cellulose stain. Later, cellulolytic effects were easily visible as large breaches formed in the walls of cells grouped around the stylet. The cellulolytic process spread centrifugally from the tip of the stylet until complete dissolution of all but the outermost walls of 6–8 cells was accomplished, leaving a typically shaped multinucleate giant cell. In one instance, nuclei from adjacent cells were observed partially drawn through apertures in the cell walls into the protoplast of an incompletely formed giant cell containing the stylet. This nuclear movement was attributed to a centripetal flow of plant juice caused by the sucking activities of the nymph. These findings do not support an earlier theory that the multinucleate giant cell was a product of plant growth, namely, enlargement of a single mesophyll cell and multiple karyokinesis or amitosis.