What is plant plumbing?

Answer 1

Water pipes, formed by the walls of dead cells, ensure the efficient transport of water and solutes in the xylem of vascular plants. In elongating plant organs such as the hypocotyl, which lifts the growing tip of the germinating seedling out of the soil, the passive elongation of dead and empty protoxylem elements by surrounding live tissue maintains a functional water-conducting system. Now, Ulrich Ryser and co-workers use confocal laser scanning microscopy to investigate a new structural element in the cell wall of protoxylem cells in hypocotyls . This structural element, which contains glycine-rich proteins , is initially deposited in the corners of cells along the longitudinal axis of the protoxylem, where it is associated with the pectin polysaccharide rhamnogalacturonan I. The authors show that the polysaccharide-rich wall of living and elongating protoxylem is gradually replaced by GRP-containing cell wall material, which develops into a complicated 3D network that seems to stabilize the protoxylem. They also report that GPR-related sequences are found in many seed plants, leading them to suggest that GRP-rich walls originated early in seed plant evolution.