![]() Thus, cell walls play a vital role in the water balance of leaf and root cells. When exposed to water, the leaf cells swell in volume, stretching the cell wall, and the elastic stretch transmits a restoring pressure force or turgor pressure to the osmotic fluids in the walls. The cell walls in leaves provide structural support and control the water relations of cells through turgor pressure. Cell walls are typically 0.5–1.5 µm thick in living leaf cells ( John et al., 2013). Relatively little quantitative information is available for the role of plant cell walls in water and solute transport in plants, except the obvious consideration that if water and solutes pass through a plasma membrane, then the water and solutes must also pass through the cell wall immediately adjacent to the membrane. The absence of pits, combined with the evidence of exclusion of solutes of molecular weight >300, explains the unexpected osmotic properties.Ĭentrifugation techniques, functional role of pits, lignified walls, Metasequoia glyptostroboides, solute exclusion, solute-free space Introduction ![]() The functional role of pits was additionally indicated by combining data in this paper with previous studies of unusual osmotic relationships in woody species that lack pits between dead wood fibers and vessels. Hence, movement of large solutes from living cells to xylem conduits is necessarily confined to pit structures that permit transmembrane solute transport via primary walls without lignin. We measured the portioning of water and solute-free space among anatomical components in stems and demonstrated that lignin impeded the free movement of solutes with molecular weight >300. Quantitative perfusion of stems with polyethylene glycol of different molecular weight was used to determine the solute-free space. Quantitative anatomical evidence was used to evaluate the water volume in xylem conduits and the water content of living cells. Centrifugation methods were used to strip water from xylem conduits, permitting a more quantitative gravimetric determination of the water and solid contents of cell walls than is possible by more traditional methods. ![]() ![]() ![]() The functional role of pits between living and dead cells has been inferred from anatomical studies but amassing physiological evidence has been challenging. ![]()
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