Yes, xylem is thick, particularly the secondary cell walls of its cells.
The thickness of xylem is a crucial adaptation that allows plants to thrive on land. Here's a breakdown:
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Support and Strength: Xylem's primary function, in addition to water transport, is to provide structural support to the plant. The thick cell walls of xylem cells contribute significantly to the plant's ability to stand upright and resist mechanical stresses like wind.
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Secondary Cell Walls: The "thick secondary cell walls" are layers of cellulose and lignin deposited inside the primary cell wall. Lignin, in particular, is a complex polymer that provides rigidity and strength. This is emphasized in the provided reference.
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Resistance to Water Pressure: Xylem cells experience negative pressure (tension) as water is pulled upwards from the roots to the leaves. The thick walls help xylem vessels and tracheids resist collapse under this pressure, ensuring continuous water transport.
Therefore, the thickness of xylem, due to its secondary cell walls, is essential for both structural support and efficient water transport in plants.
