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25-2 Plant ResponsesCh. 25: Plant Responses and Adaptations
Tropism
Response of a plant to an external stimulus
Thigmotropism
Response of plants to touch
Short-day plant
Plant that flowers when daylight is short
Long-day plant
Plant that flowers when days are long
Photoperiodism
Response of plants to periods of light and darkness
Phytochrome
Plant pigment responsible for photoperiodism
Dormancy
Period of time during which a plant embryo is alive but not growing
Abscission Layer
Layer of cells at the petiole that seals off a leaf from the vascular system
Key Concept
Plant tropisms include gravitropism, phototropism, and thigmotropism. Each of these responses demonstrates the ability of plants to respond effectively to external stimuli, such as gravity, light, and touch.
Key Concept
Photoperiodism in plants is responsible for the timing of seasonal activities such as flowering and growth
Key Concept
As cold weather approaches, deciduous plants turn off photosynthetic pathways, transport materials from leaves to roots, and seal leaves off from the rest of the plant.