1. 1 Apply Concepts Using a houseplant, a marker and a sunny windowsill, describe how you might measure the plant’s response to light 2 Review Summarize plant responses to seasonal changes 3 Explain Which type of plant- short or long day- is likely to bloom in the summer- explain Design an Experiment Design a controlled experiment to find out how a garden store owner could determine what light conditions are needed for a particular flowering plant to bloom

2. Ch 24 Plant Reproduction and Response
24.1 Plant Hormones

3. Hormones Chemical signals produced by living organisms that affect
Growth, Activity, and Development of cells and tissues
Coordinate responses to the environment.

4. Hormone-producing cells in a mature flower release hormones that travel into flower buds and inhibit development.

5. Once the mature flower is done blooming, production of the inhibiting hormone will decline, and the flower bud can then begin its bloom.

6. Target cell Hormone receptors
Portion of an organism affected by a particular hormone
Hormone receptors
Where hormone molecules bind.

7. Hormones may affect roots differently than stems or flowers and the effects may change as receptors are added or removed
All depends on the receptors.

8. Why does grass bend toward light
Darwins hypothesized that the tip produces a substance that regulates cell growth.

9. Auxins Stimulate cell elongation and the growth of new roots
Produced in the shoot apical meristem and transported to the rest of the plant.

10. Auxins and Cell Elongation
Light hits one side of the shoot
Auxins collect in shaded part of shoot
Stimulates cells on dark side to lengthen
Causes shoot to bend away from shaded side.

11. Auxins also regulate cell division in meristems
Growth at lateral buds is inhibited by auxins
Apical dominance
Lateral buds near the apex grow more slowly than those near the base of the plant
Due to more auxin at apex.

12. Cytokinins Produce effects opposite of auxins
Auxins stimulate new roots and inhibit growth of new shoot tips
Cytokinins stimulate growth of new shoot tips and inhibit new roots
Produced in growing roots and in developing fruits and seeds.

13. Gibberellins Promote germination of plants
May cause dramatic increases in size, particularly in stems and fruits
Found in the meristems of shoots, roots, and seed embryos.

14. Abscisic Acid Inhibits cell division, thereby halting growth
Stops seed growth when seed development is complete
Causes seed to go dormant
Interacts with gibberellins to control seed dormancy
Found in the terminal buds and seeds.

15. Ethylene Stimulates fruits to ripen Released from fruit
Causes plants to seal off and drop organs that are no longer needed (flower petals).

17. Tropisms
Plant response to environmental stimuli such as light, gravity, and touch.

18. Phototropism Tendency of a plant to grow toward a light source
Changes in the concentration of auxins.

19. Gravitropism Response of a plant to gravity
Auxins migrate to the lower sides of horizontal roots and stems.

20. Thigmotropism Response of a plant to touch
Vines and climbing plants wrap around objects
Grape vines have tendrils that emerge from leaf base that wrap around objects.

21. Rapid Movements Mimosa will fold in leaves when touched Venus flytrap
Osmotic pressure
Venus flytrap
Insect triggers sensory cells on the inside of the leaf, send electric signals, leaf snaps shut due to osmotic pressure and cell wall expansion.

22. Photoperiod
Plant response to the relative lengths of light and darkness
Major factor in the timing of seasonal activities such as flowering and growth
Due to phytochrome pigment.

23. Winter Dormancy
Phytochrome regulates the changes that prepare plants for winter dormancy
Deciduous plants
Turn off photosynthetic pathways
Transport materials from leaves to roots
Seal off leaves from the rest of the plant.

24. Leaf Loss Phytochrome absorbs less light as days shorten
Auxin production drops
Ethylene increases
Chlorophyll breaks down
Carotenoids (yellow and orange) become visible
Anthocyanin (red) are made.

25. Meristems produce thick, waxy scales that form a protective layer around new leaf buds
Xylem and phloem tissues pump themselves full of ions and organic compounds
Prevents tree’s sap from freezing.

26. Carrot cells were grown
in varying auxin
concentrations
1. At what auxin
concentration are the stems
stimulated to grow the most
2. How is the growth of the
roots affected by the auxin concentration at which stems grow the most
3. If you were a carrot farmer, what concentration of auxin should you apply to your fields to produce the largest carrots