SECTION 3 .4UNIT C

Transport in Plants

Objectives

distinguish between cohesion and adhesion, giving examples

describe water transport from root to leaf including different processes used

relate tonicity of plant environment to movement of water in and out of the cell

summarize the process of sugar transport in plants

Review

What is osmosis?What is diffusion?What is active transport?What is transpiration? Where does it take

place?

Plant Transport of Water: 3 Main Steps

1) Water uptake in roots – root pressure2) Cohesion & Adhesion in Xylem 3) Leaf transpiration

Animation:

http://www.biology.ualberta.ca/facilities/multimedia/uploads/alberta/transport.html

Root Pressure

Movement of water from roots to leavesPressure built up in xylemDissolved minerals in root cells due to active

transportWater enters cell, creating positive pressure,

forcing fluid up the xylemWater forced from area of higher pressure in

roots to area of lower pressure in leaves

Root Pressure

When would root pressure not be the complete explanation for water movement in plants? When the plant is very large (maximum of a few

metres)Overall process affected by transpiration

Cohesion and Adhesion

Cohesion Attraction of water molecules to other water

molecules Due to polar nature of water (slightly positive end

attracts slightly negative end of another water molecule)

Cohesion and Adhesion

Adhesion Attraction of water molecules to molecules of other

substances Usually polar interactions

Cohesion & Adhesion in the plant

Cohesion and adhesion are two properties of water that helps it to travel from roots to leaves.

Cohesion Causes water molecules to cling to each other

Adhesion allows water to pull itself up the plant

Video: http://www.youtube.com/watch?v=EKyHbanzYnI&feature=related

Trees & Capillary Action: http://www.davidlnelson.md/Cazadero/Trees&CapillaryAction.htm

Transpiration

Evaporation of water through stomata and lenticels through transpiration creates a tension or transpiration pull.

When combined with cohesion, adhesion, and root pressure, water is able to be drawn up the xylem.

Transpiration is dependent on temperature. Higher temperatures increase the rate of evaporation and cause rapid movement in xylem.

Video: Plant Transport - Summary

http://www.youtube.com/watch?v=U4rzLhz4HHk&feature=related

Why would the carnation/celery change color?

How is it related to root pressure and transpiration? Transpiration causes the loss of water through the

stem and leaves. This water must be replaced, drawing water up from

the roots Note that only certain cells in the celery are stained

Which cells might these be? Xylem

Do Now

Individually, write a story of water transport in a large plant using the information on p. 317-318. You are writing it from the point of view of the water molecule.

Explain in your story how the plant uses adhesion and cohesion properties of water to its advantage

Include the different transport mechanisms used at different parts of the plant Root Pressure, Adhesion, Cohesion, Transpiration

Tonicity & its Effect on the Plant

Tonicity concentration of solute particles in an solution Related to hypertonic and hypotonic (which one would

have a higher tonicity?)What will happen to a plant cell that is placed

in a concentrated salt solution? Water leaves the plant cell by osmosis Effect = plasmolysis (cell looks shrunken) Water leaves vacuole, cell contents pull into center, cell membrane becomes visible

Hypertonic solution

Hypotonic solution

Question

What would happen to a plant that was placed in a hypertonic solution (salt solution)? Becomes flaccid

What would happen to the plant when it was moved from this solution to a hypotonic environment? Becomes turgid

Sugar Transport

Phloem is essential Removal causes plant death

Takes sugar from source (leaves) to place to be used/stored (sink)

Composed of sieve tube cells Need companion cells to control its activity Why? Uses carrier proteins and active transport to take in

sugar molecules

Sugar Transport

If sugar is being moved into the cells, what else will follow it? Water!

Increased pressure pushes water and sugars through phloem to rest of plant

Called the pressure-flow theory

Sugar Uses

Actively transported from sieve cells in phloem to adjacent cells

Use: Growth Respiration Other life processes

Stored in roots, stems, or leavesWater follows movement of sugar and can:

Increase turgidity of other cells Leave through transpiration Move into xylem