Transcript Plant Transport and Tropisms

Plant Transport
• Water Transport
– 1. Enters root by osmosis
– 2. Passes through cortex
(parenchyma) tissue by
osmosis
– 3. Passes through
endodermis
• One way only
• Combination of active
transport and osmosis
Plant Transport
• Water Transport (cont)
4. Enters xylem
• Cohesion– The attraction of
water molecules to
each other
• Transpiration– The evaporation of
water from the
leaves of plants
Plant Transport
• Water Transport (cont)
– 5. Transpiration Pull• The force that pulls water
upward.
• Cohesion holds the water
column together as it
moves upward through
the xylem
Plant Transport
• Food Transport
– Requires energy (active
transport)
– Translocation• Movement of food
through the phloem
– Pressure Flow
Hypothesis (source-sink)
• Food moves from an area
of high pressure to low
pressure
Plant Transport
• Food transport
– High Pressure (Source)• Could be leaves when
food is formed
• Could be areas of food
storage (root, stem, etc)
– Low Pressure (Sink)• Could be where food is
used for growth.
• Could be where food is
stored.
Plant Motions
•
Auxins–
Plant hormones
•
•
–
Stimulate or inhibit
cells to grow
Depends on the target
organ
Stem growth•
–
Auxins stimulate stem
cell growth
Root growth•
Auxins inhibit root cell
growth
Plant Motions
•
Tropism– Response of a plant to
environmental stimuli
– Positive•
Respond toward the
stimulus
– Negative•
Respond away from the
stimulus
Plant Motions
•
Phototropism–
Response of plants to
light
•
Stem- positive
Plant Motions
• Gravitropism or
geotropism– Response of plants to
gravity
• Stem- negative
• Root- positive
Plant Motions
• Thigmotropism– Response of plants to
touch
• Tendril- positive
Flowering
•
Photoperiodicity–
•
Response of flowering
plants to different light
conditions
Short day plants–
–
Flower when time
exposed to light is short
ex. chrysanthemums &
poinsettias
Flowering
• Long day plants– Flower when the
amount of time exposed
to light is long
– ex. clover, petunias, &
hollyhocks
Flowering
• Day-neutral plants– Length of light has no
effect on flowering
– ex. corn & tomato
• Actually the amount of
darkness, not light, that
stimulates these plants