35 Structure, Synthesis, and Function of the Plant Cell Wall

Abstract

The cell walls of higher plants form a contiguous scaffold surrounding the individual protoplasts within the plant body. In addition to providing mechanical support for the cells, plant cell walls have a pivotal role in growth and development, in cell-cell recognition and interaction, and in defense responses (for recent reviews, see Roberts 1990; Levy and Staehelin 1992; Carpita and Gibeaut 1993). In contrast to animal systems, cell migrations make little contribution to plant development; instead, the ordered formation of plant tissues and organs relies solely on the combination of two processes: the division of cells in specific planes, and the subsequent three-dimensional expansion of the cells in specific dimensions. This latter process of extension growth is primarily a function of the mechanical properties of the walls and the synthesis of new cell wall material. Since all cells within a growing tissue or organ are held together via their middle lamella, extension growth needs to be tightly coordinated between the various cell types in growing parts of the plant body. Since different cell types within a growth zone are distinguished not only by their shape and size, but also by the thickness of their walls, a very complex network of regulatory mechanisms is required to ensure the ordered formation of plant tissues and organs.

Cell wall formation in higher plants essentially takes place in three stages: cell plate formation, extension growth, and secondary growth. The cell plate is a structure formed during the final stages of cell division by the fusion...