Functions of Parenchyma Cells in Wood; Material Transport and Heartwood Formation

The parenchyma cells in wood survive and keep their physiological activity for a long time, from a few years to several decades, whereas the vessel elements, tracheids, and wood fiber, which function as water conduit or strengthen the stem, die immediately after cell maturation. Parenchyma cells play important roles for the trees’ longevity. Functional material transport is necessary for the parenchyma cells to store and recycle the materials for the trees’ growth. Also, during heartwood formation, reserve materials convert into heartwood substances and cell death of the parenchyma cells occurs. This text focuses on material transport and heartwood formation, and reviews recent studies as well as presents challenges to future studies of these functions.