1. WEDNESDAY 2/10/16 Learning Goal: Identify the stimuli that produce plant responses. Warm up: Finish labeling flower parts Homework: Finish packet pages 37-39

2. PLANT RESPONSES AND GROWTH CHAPTER 8 SECTION 5

3. TROPISM A plants growth response toward or away from a stimulus Plant grows toward a stimulus: positive tropism Plant grows away from a stimulus: negative tropism Three important stimuli Touch Light Gravity

4. EXAMPLES OF TROPISMS Plant showing response to touch Thigmotropism Positive tropism Grows toward object they are touching Example: bladderworts, grapes, morning glories

5. EXAMPLES OF TROPISMS Plant showing response to light Phototropism Positive tropism Grows toward light

6. EXAMPLES OF TROPISMS Plants showing response to gravity Gravitropism Negative tropism on stem Gravity it pulling down, yet plant grows up Positive tropism on roots Roots grow down, direction gravity pulls

7. HORMONES AND TROPISMS Hormones Produced by a chemical that affects how the plant grows and develop Auxin Speeds up the rate at which a plant’s cell grows Plants hormones also control… Tropism Germination Formation of leaves, stems, roots Shedding of leaves Development/ripening of fruit

8. HOW DOES AUXIN CONTROL A PLANTS RESPONSE TO LIGHT Auxin builds up in shaded side of a stem Cells on shaded side of the stem begin to grow faster Cells on stem’s shaded side are longer than those on sunny side Stem bends toward light

9. SEASONAL CHANGES: PHOTOPERIODISM What triggers a plant to flower? The amount of DARKNESS a plant receives Photoperiodism A plant’s response to seasonal changes in length of night and day Critical night length The number of hours of darkness that determines whether or not a plant will flower

10. LONG-DAY/SHORT-DAY PLANT Short-day plants Flower when nights are longer than a critical length (fall/winter) Long-day plants Flower when nights are shorter than a critical length (spring/summer) Day-neutral plants Flowering cycle is not sensitive to period of light and dark

11. DORMANCY A period when an organism’s growth or activity stops

12. LIFE SPANS OF ANGIOSPERMS Annuals Angiosperms that complete a life cycle within one growing season Most have herbaceous stems Biennials Angiosperms that complete a life cycle in two years Once flowers produce seeds, the flower dies Perennials Angiosperms that live for more than two years Ex. peony