1. Plant Processes 8 th 15.2 Plant Responses

2. Plant Responses Tropism – response of a plant to an outside stimulus Tropism – response of a plant to an outside stimulus Stimulus that affects a plants growth Stimulus that affects a plants growth Light, heat, moisture, gravity, electricity, touch and chemicals. Light, heat, moisture, gravity, electricity, touch and chemicals. Positive - grows toward stimulus Positive - grows toward stimulus Negative – grows away from stimulus Negative – grows away from stimulus

3. Plant Responses

4. Phototropism Phototropism Gravitropism Gravitropism Thigmotropism Thigmotropism Auxin – plant hormone that lengthens cells Auxin – plant hormone that lengthens cells Ethylene – plant hormone that causes fruit to ripen Ethylene – plant hormone that causes fruit to ripen

5. Plant Responses

6. Photoperiodism – plants response to the number of hours of daylight and night Photoperiodism – plants response to the number of hours of daylight and night Long day plants - petunias, lettuce, wheat, barley, carnation, radish, tobacco Long day plants - petunias, lettuce, wheat, barley, carnation, radish, tobacco Short day plants – onion, sugar cane, blueberry, rhododendron, marijuana Short day plants – onion, sugar cane, blueberry, rhododendron, marijuana Day neutral plants Day neutral plants

7. Plant Responses