22.5 Plant Hormones.ppt yang disesuaikan dengan

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1. 22.5 Plant Hormones and Responses
KEY CONCEPT
Plant hormones guide plant growth and development.

2. 22.5 Plant Hormones and Responses
Plant hormones regulate plant functions.
•Hormones are chemical messengers.
–produced in one part of an organism
–stimulates or suppresses activity in another part

3. 22.5 Plant Hormones and Responses
–ending seed dormancy
–Stimulates stem
elongation, germination,
and flowering
•Gibberellins are plant hormones that produce dramatic
increases in size.

4. 22.5 Plant Hormones and Responses
–some fruits picked
before they are ripe
–sprayed with ethylene to
ripen when reach
destination
•Ethylene causes the ripening of fruits.

5. 22.5 Plant Hormones and Responses
–final stage in cell division
–produced in growing roots, seeds, and fruits
–involved in growth of side branches
•Cytokinins stimulate cytokinesis.

6. 22.5 Plant Hormones and Responses
•Auxins lengthen plant cells in the growing tip.
–stimulates growth of
primary stem
–controls some forms of
tropism
* A tropism is the movement
of plant in response to an

environmental stimulus. *

7. 22.5 Plant Hormones and Responses
Plants can respond to light, touch, gravity, and seasonal
changes.
•Phototropism is the
tendency of a plant to
grow toward light.
–auxins build up on
shaded side of
stem
–cells on shaded
side lengthen
–causes stem to
bend toward light

8. 22.5 Plant Hormones and Responses
–climbing plants and vines
–plants that grow in direction of constant wind
•Thigmotropism is a plant’s response to touch-like stimuli.

9. 22.5 Plant Hormones and Responses
–positive gravitropism is downward growth (roots)
–negative gravitropism is upward growth (shoots)
•Gravitropism is a plant’s growth or turning in response
to gravity.

10. 22.5 Plant Hormones and Responses
–Some responses protect
plants from predators.
–Some responses allow
plants to capture food.
•Some plants have rapid responses not involving growth.
When leaves of a Venus
Fly Trap are touched,
water rushes to the cells
in the bases of the leaf
making it bend inward- -
- closing the “mouth” of
the plant!

11. 22.5 Plant Hormones and Responses
–triggers some plants to flower
–triggers fall colors/winter dormancy of deciduous trees
•Photoperiodism is a response to seasonal changes in
day length.

12. 22.5 Plant Hormones and Responses
Asexual Plant Propagation Lab
•For this lab, you will be conducting plant propagation using a
philodendron plant.
•The first step in plant propagation from existing plants is to take cuttings.
•Before making a cut, look for nodes—these are the beginnings of new
leaves and stem systems and resemble small roots or buds.
•After you have cutting, place the cutting in a cup with water reaching right
below the leaf, but above the nodes.
•Record your observations for day 1 (drawing and written description).
•You will make weekly observations and drawings. At the end, you will
construct a line graph to show your results.