Water Relations b How water and minerals flow through the plant.

Water Relations b How water and minerals flow through the plant. b Why does the plant need water?

Water Relations b How water and minerals flow through the plant. b Why does the plant need water? TurgidityTurgidity growthgrowth photosynthesisphotosynthesis cooling (evaporative)cooling (evaporative) solvent/metabolic mediumsolvent/metabolic medium

Movement of Water?

Movement of Water b Leaves -> b stem-> b roots ->

Leaf Structure

Purpose of Stomata (?)

b Gas Exchange

Purpose of Stomata (?) b Gas Exchange C02 and H20C02 and H20 TranspirationTranspiration Trade Off (?)Trade Off (?)

Purpose of Stomata (?) b Gas Exchange C02 and H20C02 and H20 TranspirationTranspiration Trade Off:Trade Off: –How can a plant take in adequate carbon dioxide without losing too much water??? –Natural adaptations –Synthetic solutions - antitranspirants

Leaf Structure

Diffusion? b (Much of what happens during water transport depends on physical laws and the physical characteristics of water.)

Diffusion

Diffusion b b The movement of molecules from an area of greater concentration to an area of lesser concentration. b b TKE Translocational Kenetic Energy b Solute & Solvent

Laws of Thermodynamics b First b Second

Laws of Thermodynamics b First the total amount of energy in the universe is constant. Can change from one form to another.the total amount of energy in the universe is constant. Can change from one form to another. b Second

Laws of Thermodynamics b First The total amount of energy in the universe is constant. Can change from one form to another.The total amount of energy in the universe is constant. Can change from one form to another. b Second The total amount of free (usable) energy is declining.The total amount of free (usable) energy is declining. Some energy lost as heat of every transfer.Some energy lost as heat of every transfer.

Osmosis?

Osmosis

Osmosis b The movement of water through a differentially permeable membrane.

Solutions b Hypotonic - lesser concentration of solute on the outside of the cell. (Turgor Pressure)

Solutions b Hypotonic - Lesser concentration of solute on the outside of the cell. (Turgor Pressure) b Hypertonic - Greater concentration of solute on the outside of the cell. (Plasmolysis)

Solutions b Hypotonic - Lesser concentration of solute on the outside of the cell. (Turgor Pressure) b Hypertonic - Greater concentration of solute on the outside of the cell. (Plasmolysis) b Isotonic - Equal concentrations of solutes on the inside and outsides of the cell.

Plasmolysis & Turgor Pressure

Properties of Water b 1. Dipolar -

Properties of Water

b 1. Dipolar - b 2. Universal solvent b

Properties of Water b Hydrated shells -

Properties of Water

b 1. Dipolar - b 2. Universal solvent b 3. As solutes are added to pure water the boiling point increases and the freezing point depression decreases.

Properties of Water b 3. As solutes are added to pure water the boiling point increases and the freezing point depression decreases. Freezing Point Determination for osmotic pressure (O)

Properties of Water b Osmotic pressure b (O)

Properties of Water b Plasmolytic Method for (O) series of sugar solutions:series of sugar solutions: 0.2M 0.3M 0.4M 0.5M ………0.2M 0.3M 0.4M 0.5M ………

Incipient Plasmolysis

Properties of Water b Plasmolytic Method for (O) series of sugar solutions:series of sugar solutions: 0.2M 0.3M 0.4M 0.5M ………0.2M 0.3M 0.4M 0.5M ……… use plant cells - epidermal tissueuse plant cells - epidermal tissue check for incipient plasmolysis O solution = O cellscheck for incipient plasmolysis O solution = O cells

Osmotic Potential (O) of a Plant b Gravimetric Method for O determination: 1. Series of Known sucrose solutions:1. Series of Known sucrose solutions: 2. Cylinders of plant tissue in each solution2. Cylinders of plant tissue in each solution –0.5M Bars – Bars – Bars 3. Determine wt. Loss or gain - (No change in wt. = O of plant cells.)3. Determine wt. Loss or gain - (No change in wt. = O of plant cells.)

Osmotic Potential (O) of a Plant b Chardakoff Falling Drop Method for W determination: 1. Series of Known sucrose solutions:1. Series of Known sucrose solutions: 2. Cylinders of plant tissue in a series of each solution and MB in another series2. Cylinders of plant tissue in a series of each solution and MB in another series –0.5M Bars tissue … MB – Bars tissue … MB – Bars tissue … MB 3. If tissue absorbs water (O > sol) = drop rises3. If tissue absorbs water (O > sol) = drop rises If tissue emits water (O < sol) = drop falls If tissue emits water (O < sol) = drop falls

Overall Water Status of a Plant b Water Potential (W) = b Osmolarity (O) + Wall Pressure (P) b W = O + P

Overall Water Status of a Plant Pressure Bomb Method for determining W:Pressure Bomb Method for determining W: (direct measurement - most accurate)(direct measurement - most accurate) –1. Place plant part in pressure chamber with cut stem on the outside. (Cut stem usually shows water under tension.) –2. Increase pressure inside of chamber until water droplets pushed out of cut stem. Pressure reading at this point = W

Overall Water Status of a Plant Water Potential ( W)Water Potential ( W) Water tends to move from cells that have relatively high (less negative!) water potentials to cells that have lower (more negative) water potentials!!Water tends to move from cells that have relatively high (less negative!) water potentials to cells that have lower (more negative) water potentials!!

Overall Water Status of a Plant Water Potential ( W)Water Potential ( W) …………………………..…………………………..

Overall Water Status of a Plant Water Potential ( W)Water Potential ( W) Water tends to move from cells that have relatively high (less negative!) water potentials to cells that have lower (more negative) water potentials!!Water tends to move from cells that have relatively high (less negative!) water potentials to cells that have lower (more negative) water potentials!! Soil --> Root --> Stem --> Leaves --> AtmosphereSoil --> Root --> Stem --> Leaves --> Atmosphere