Chapter 34: Roots and Minerals
Roots-more extensive than shoot
ex. cornplant- 4 ft. tall, roots 8 ft. deep and 4 ft. across
- anchorage
- absorbing/absorbtion (water, minerals)
- storage ( surplus sugar stored in roots) (tap roots- carrots, beets, radished, turnips) (fibrous roots- sweet potatoes, yams
Tap roots- one main root, develops from embryonic root in seed (radicle)
tap root dies, surface roots form (lateral and shallow)
exception-Hickory tap roots do not die
Fibrous Root Systems
- embryonic root dies early on and is replaced by meristematic tissue at bottom of stem
- adventitious- roots that develop from stem tissue, not embryonic roots
- taproots- absorbs deep ground water
- fibrous- absorbs water on surface (rain)
Exterior Structure
root cap- protects meristem, replaced by mitosis(apical meristem)
- root cap cells- gravity detectors
- if root cap is cut, root cap eventually regenerates and directs roots in proper direction
Root hairs- extensions, short-lived, 1 cm(.5 inch)
Transport in xylem- one-way movement
- water moves horizontally into root
- meets xylem, moves vertically: PASSIVE
- pull from top, explained by tension/cohesion theory
- cohesion strong enough to pull water up 500 ft.
- cohesion due to water being a polar molecule
Root Pressure: ?push? on water, works in spring (moist soil)
- plant cells split ATD, use energy to pump ions to xylem
- water follows by osmosis
- have upward and increase water pressure in xylem
- forces water upwards: guttation
Sugar Movement: sugar is formed during dark reaction of photosynthesis
photosynthesis>>>glucose>>>fructose/sucrose(disaccharide)>>>loaded into phloem (sieve tube)>>> Sink(roots, meristems, flowers, fruits)
parenchymal in mesophyll (Source)
Pressure flow hypothesis:
- high pressure>>>low pressure
- linked cotransport: H+ gradient pulls in sugar
- also transports plant hormones, ATP, amino acid, ions(K+, Na+) and pathogens (ex. Tobacco mosaic virus
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