Chapter 36 Notes Transport in Plants

Concept 36.1

Transport in plants occurs on 3 levels - the uptake and loss of water by individual cells - short distance transport of substances from cell to cell at the level of tissues and organs - long distance transport of sap within xylem and phloem of the whole plant

Concept 36.1 Uptake and loss of water by cells - plant cell membranes are selectively permeable - use of transport proteins /selective channels - transport can be active or passive

Concept proton pump: hydrolyzes ATP and uses the released energy to pump H + ions out of the cell - forms a H + gradient - plant cells use the energy from the gradient to drive the transport of many different solutes - ex. movement of K +

Concept 36.1

Differences in water potential drive water transport in plant cells Osmosis: the net uptake or loss of water by a cell - high concentration to low In plants, the cell wall makes physical pressure a factor of osmosis

Concept 36.1 Water potential: the combined effect of solute concentration and pressure. - psi (  ) - water will move from the solution with the higher water potential to the solution with the lower water potential

Concept 36.1

The combined effects of pressure and concentration -  =  P +  S -  P : pressure potential -  S : solute potential

Concept 36.1

Bulk flow functions in long distance transport Bulk flow: the movement of fluid driven by pressure - water and solutes move the xylem vessels and sieve tubes - transpiration reduces pressure in xylem which creates tension

Concept 36.2 Most absorption occurs near root tips - soil particles adhere to root hairs - the soil sln. flows into the walls of the epidermal cells and into the root cortex - mycorrhizae absorb water and minerals and then transfers them to the plant

Concept 36.2

Concept 36.3 Root pressure: water flows in from the root cortex, generating a positive pressure that forces fluid up the xylem Root pressure causes guttation: when more water enters leaves than is transpired and the excess is forced out Root pressure can only force water up a few meters, not the major force

Concept 36.3 Pulling up xylem sap: Transpiration- Cohesion-Tension Theory Transpiration -when stomata open water exits the leaf - move from [high] to [low]

Concept 36.3

Cohesion - water molecules will bond to each other with hydrogen bonds - water molecules exiting the xylem tug on adjacent molecules - the pull is relayed

Concept 36.3 Tension - the upward pull creates tension within the xylem - the small diameter of the tracheids helps overcome the force of gravity