Cell-Cell Communication in Wood
The sapwood of trees contains living cells in the form of ray and axial parenchyma. Communication between these cells is important in controlling the differentiation of xylem cells, movement of nutrients and water, defence against pathogens and damage repair. These parenchyma cells are therefore linked symplasmically by plasmodesmata enabling them to coordinate their activities. This chapter reviews the distribution of plasmodesmata in mature sapwood and the cambium and differentiation zone in an attempt to explain their role in the wood. The extent to which symplasmic connections are important in unloading nutrients into the cambium and zone of differentiating wood cells is confused by the fact that many of the differentiating cells appear to be isolated from the symplasm. This suggests that these cells rely on the apoplasmic pathway for input of nutrients, and that secondary formation of plasmodesmata may be one factor in the control of the fate of differentiating wood cells.