PLS 170C1 Lecture Notes - Lecture 6: Cork Cambium, Vascular Cambium, Xylem
Document Summary
To stand upright, stems of both herbaceous dicots and monocots require thick walled. Turgor pressure increases as water enters the cell and pushes the plasma membrane to push against the cell wall. This hydrostatic pressure allows stems and leaves of herbaceous plants to stand upright. Plasmolysis occurs when so much water is lost that the plasma membrane shrinks away from the cell wall. Woody plants (trees) need more than turgor pressure in stems to stand upright. They strengthen their stems in diameter by producing layers of secondary xylem (wood) as they grow tall. Woody stems consists of the three primary tissue systems and secondary tissues produced by lateral meristems including: Vascular cambium makes 2 xylem (wood) and 2 phloem. Cork cambium makes the outer bark (periderm). Tree bark consists of crushed secondary phloem and periderm. Wood consists of layers of hollow, thick walled. 2 xylem cells produced annually from vascular cambium.