Biology

Topics: Leaf, Plant physiology, Xylem Pages: 3 (682 words) Published: May 18, 2013
Arrangement of Vascular Tissues in Flowering Plants

• Xylem and phloem often are grouped together -> vascular bundle • Cambium -> lies in between xylem and phloem -> divide and differentiate -> form new xylem and phloem tissues -> thickening of stem

Movement of Substances Into and Within Flowering Plants
Entry of Water and Nutrients into Plants
• Absorption of water -> root hairs -> grow into close contact with liquid around them • Thin film of liquid surrounding soil particle -> dilute solution of mineral salts • Cell sap in root hair -> lower water potential than surrounding soil solution -> separated by partially permeable membrane • Water enter root hair cell by osmosis/active transport • Mineral salts -> diffusion and active transport

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How is the structure of root hair cell adapted to its function of absorption? • Elongated protrusion that increases surface area to volume ratio -> increase efficiency of absorption of water and mineral salts • Root hair grow between soil particles -> close contact with surrounding water

Active transport: when concentration of ions in soil solution is lower than that in root hair cell sap Diffusion: when the concentration of ions in soil solution is higher than that in root cell

Movement of Water in Root
• Entry of water dilutes cell sap of root hair cell, such that is of a higher water potential than that of the next inner cell in cortex or cortical cell • Water passes by osmosis from root hair cell into inner cortical cell • Continues until water enters xylem vessels -> moves up plant by transpiration pull Movement of Water Against Gravity Up a Plant

1. Transpiration pull
• Provides a suction force -> main factor that cause movement of water up xylem 2. Capillary action
• Water tends to move up inside very narrow tubes ( capillary tube due to cohesion between water molecules) , as well as adhesion of water molecules on surfaces of...
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