Peterson, R. L. Department of Botany and Genetics, University of Guelph, Ontario, Canada.
- Location and function
- Occurrence in plant groups
- Related Primary Literature
- Additional Reading
Plant cells characterized by the elaboration of an unlignified, secondary cell wall to form fingerlike projections or wall ingrowths which protrude into the cytoplasm of the cell (Figs. 1 and 2). These ingrowths are enveloped by plasma membrane (Fig. 2), forming a wall-membrane apparatus. The extent of wall ingrowth development varies from small, conical projections, through long, unbranched or branched structures, to Y-shaped flanges. In all cases their formation increases the surface-volume ratio of the cell, which implicates them in short-distance solute transport. The surface area of the plasma membrane may be increased up to 20 times that of a similar-sized cell lacking wall ingrowths. Most transfer cells elaborate numerous mitochondria (Fig. 2), many in close association with the wall ingrowths, suggesting that the transport process is energy-requiring. An enlarged, lobed nucleus (Fig. 2) and numerous endoplasmic reticulum cisternae and ribosomes are often characteristic of the cytoplasm of transfer cells. Plasmodesmata (cytoplasmic channels for intercellular transport) connect transfer cells to other transfer cells and to parenchyma cells (Fig. 2).
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