Landscape Management EOPA Practice Exam

Water moves upward through a plant mainly through xylem, the tissue built for transporting water and minerals. Xylem consists of hollow, dead cells with thick, lignified walls that form continuous conduits from roots to shoots. Water is pulled upward by the tension created when it evaporates from the leaves (transpiration). This pull is facilitated by cohesion between water molecules and adhesion to the xylem walls, creating a continuous column that can travel against gravity. Root pressure can contribute a little at times, but it’s the transpiration-driven cohesion-tension system that drives most of the ascent. Phloem, in contrast, transports sugars and other nutrients, not water movement upward. Cambium is a growth layer that produces new xylem and phloem, and parenchyma is storage tissue, not the main water-conducting tissue. So the tissue carrying water upward from the roots is xylem.