Section 3.4 Transport in Plants

Cohesion & Adhesion Water clings to each other, and to other molecules Helps aid in transport of water Attraction of water molecules to each other is called cohesion

Cohesion & Adhesion Due to polar nature of water molecules Remember, positives and negatives attract Also means water is attracted to other molecules The attraction of water molecules to other substances is called adhesion

Root Pressure Rate of transpiration is low Roots still collecting minerals Water is forced from higher pressure in roots to lower pressure in leaves

Water Transport Transport of water in plants is due to a combination of factors Differences in pressure caused by osmosis & transpiration See diagram in text on pg 318 for summary

Water Transport Evaporation of water through stomata or lenticels creates Tension (or) transpiration pull This draws water up xylem to leaves Then can be moved into ground tissue and out through stomata In ideal conditions, water can move 75 cm per MINUTE!!

Tonicity Tonicity refers to solutions being hypertonic, hypotonic or isotonic When solute concentration around a plant cell changes, there is an effect on the cell

Tonicity Plasmolysis  shrinking of cytoplasm and plasma membrane away from cell wall Due to outflow of water in hypertonic solution Observed only in cells with rigid cell walls

Sugar Transport What happens if you removed the phloem? Plant would die Cells would not be receiving products of photosynthesis

Sugar Transport Where sugar is manufactured The leaf Called the source Where sugar is used or stored Throughout the plant Called the sink

Section 3.5 Control Systems

Response to Stimuli Not as pronounced as in animals Do have responses to specific stimuli Light Gravity

Response to Stimuli Plants grow towards light Phototropism Movement of the plant in response to the stimulus Shoots towards light Roots away from light

Response to Stimuli Response to gravity Called gravitropism Roots grow towards gravitational force Shoots grow away from it

Tropisms Plant Part Stimulus Tropism Stem Light Positive phototropism Root Weak negative phototropism Gravity Negative gravitropism Positive gravitropism

Auxin Another plant hormone Ability to initiate cell elongation response Discovered by F.W. Went in Holland

Other Control Mechanisms Respond to touch To temperature, chemicals and water To photoperiod

Germination Need specific conditions Water Oxygen Temperature should be a moist environment Oxygen plenty of access Temperature usually around 15°C moderate

Apical meristems responsible for plant length Found in roots and shoots Lateral meristems responsible for increase in plant girth