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Transport in Angiosperms9.2 part 1
Roots
A. Plants take in water and minerals through their roots
B. Roots have large surface area to allow for adequate uptake of water and minerals
-they are branched and they have root hairs
C. Function of the cortex=to facilitate water uptake
D. Roots also act as anchorage to ground
Zone of maturation: cells differentiate into different types of cells
Zone of elongation: allows the root to get deeper within the soil
Meristematic region: rapid mitosis of undifferentiated meristematic cells
Root cap: protects the meristematic region
Roots and active transport
A. Mineral concentrations are often higher in the root than in the soil
B. This suggests active transport (going against the concentration gradient)
C. Cortex cells can absorb ions that are dissolved in the water that is drawn by capillary action through the cortex cell walls
Water Uptake By Roots
Roots take in water via osmosis
-Water in the soil contains a lower concentration of solutes than the cytoplasm of root
cells
-This causes water to diffuse in to the roots
High solute Low solute
Root cell Soil
H2OH2O
Water Uptake by Roots
**Water diffuses (osmosis) to an area of high solute concentration to reach equilibrium between the roots and the soil **Minerals are taken in via active transport because the roots have higher solute concentration than the soil
Water Uptake By Roots (continued)
Most absorbed water is eventually drawn to the rest of the plant because of transpiration
-as water exits the leaves it must be replaced
To get water from the root hairs to the xylem, there are two possible methods
-apoplast or symplast
Apoplast pathway
-water does not enter the root cells
-it travels by capillary action through the cell walls of the cortex until it reaches the endodermis
-cells of the endodermis have Casparian strips around them that are impermeable to water
-to pass through the endodermis the water must follow the symplast pathway (the apoplastpathway stops at the endodermis)
Symplast Pathway
-water enters the cytoplasm of the cells, but not the vacuole
-water passes from cell to cell via the plasmodesmata(connections of cytoplasm between cells)
-the water eventually enters the xylem
Movement Through Roots
Assignment: (in notebook)
Make a chart to compare apoplastand symplast pathways
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