On the Mechanism of Xylem Vessel Length Regulation

The mechanism by which the plant regulates the length of xylem vessels has not yet been elucidated. The length of a xylem vessel depends on the number of fused vessel elements and their individual lengths. In this paper, a straightforward mechanism is postu- lated to explain how the length of xylem vessels in plants is regulated. The mechanism is based on a steerable, similar chance for all tracheary elements to be a terminal element. As a result, an exponential vessel length distribution is created with mostly short and fewer long vessels, as is commonly found in plants. Angiosperm plants have xylem vessels, which are responsible for long-distance transport of water and nutrients. During vascular development, single cells fuse into linear strings. After fusion and formation of a secondary cell wall, these tracheary elements lose their nucleus and cell contents, leaving a hollow, dead, finite capillary (the vessel). Xylem vessels are