L26 - Cell Movement : Plants

Osmosis

= net movement of water molecules

• powers movement of plants

Rapid changes in water pressure

• ion channels are gated → water follows the ions

Plant cell expansion:

ex. venus fly traps

• uses Ca2+ gradient → water enters → outer cells expand → envelope/fold over to capture insects

Steps:

1. insect touches hairs

2. action potential

3. gated ion channels open

4. Ca2+ enters outer cells

5. water enters outer cells (following ions)

→ outer cells get larger → leaf folds inwards

ex. cape sundews - also moves leafs to capture insects

Slow Changes in water pressure

• central vacuole contains some pH sensitive pigments

• central vacuoles are acidic bc of ATP powered proton-pumps

• petals expand when water enters central vacuole

ex. flowers blooming

ex. Morning Glory flowers = bloom in morning from water entering

• NHX1 (present when morning glory flower blooms): a H+ powered K+ antiporter transporter that moves K+ ions into the CV

  • H+ exit CV & K+ enter CV

Extreme changes in water pressure

• during cell decomposition (few large things→ many little things), water enters → creates pressure

ex, squirting cucumber - disperses its seeds by increased water pressure

Examinable content

• ions enter cell → water follows ions and enters the cell → increased water pressure → cell expansion

• cell interior dies → water enters cell → increased water pressure → weakened connection → burst open to spread seeds