Download Science 10 Unit C Biology C3.4 and C3.5

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
Root
Light
Stem
Gravity
Root
Gravity
Positive
phototropism
Weak
negative
phototropism
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
 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