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