Dynamic dead cells are revealing how plants control the flow of water through their stems. A report in Science News , vol 159, p53, 27 Jan 2001 describes experiments on xylem, a plant’s internal plumbing system formed by stacks of dead cells. When the concentration of dissolved salts in water flowing through the xylem increases, pores in the cells enlarge so that more water can flow through the pipes. The regulator appears to be a hydrogel substance built into the membranes between cells. It becomes more porous (leaky) when salt concentration increases. According to the scientists who carried out the study this system enables plants to maintain high flow of water to branches that receive a lot of sunlight and are therefore metabolically active. Water evaporates more rapidly from these, which increases the salt concentration causing the pores in the xylem to open up and increase the flow.

Editorial Comment: Such a chicken and egg situation in this sophisticated plumbing system is one more evidence of forward planning by an intelligent designer. Without a functional leaf and vein and stem system there would be no need for hydrogels. Without the hydrogel there could be no water flow. All has to be present or none of it works. (Ref. xylem, plants, design)