31 FlowerPlantsBB - The pipes and valves of plant plumbing...

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Sugar movement The pipes and valves of plant plumbing Xylem tissue: vessels, tracheids Phloem tissue: Sieve cells, companion cells Stomata, Guard cells valves Transport of substances 1. Water transport: Water and solutes (inorganic nutrients) up the plant from root up to other parts 2. Assimilate transport: Sugars (organic nutrients) from source to sink from leaf (=source) to root (=sink) or flower (= sink) Plants use lots of water; it is transported in the xylem A sunflower plant uses, on a weight basis, ~ 20x more water than a human On a summer’s day, a large tree uses hundreds of gallons of water
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So, what’s the problem? 92 m (=275 ft) tall Eucalyptas regnans at Wallaby Creek, Victoria, Australia Water rises in narrow tubes due to the capillary forces of cohesion and tension Capillary rise depends on the radius of the tube Radius 25 μ m 0.025 mm Height 0.6 m Radius 10 m -8 0.000001 mm Height >1km Where are the capillary tubes in plants? Xylem tissue in vascular bundles contains narrow,
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31 FlowerPlantsBB - The pipes and valves of plant plumbing...

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