Tropisms, Nastic Movements, & Photoperiods Plant Growth & Development Tropisms Defined as: ______3 Types: - Phototropism - ______- Thigmotropism Tropisms Defined as: Plant growth responses to environmental stimuli that occur in the direction of the stimuli 3 Types: - Phototropism - Gravitropism - Thigmotropism Phototropism
Defined as: the tendency of a plant to grow toward a light source Cool corn - Can be within hours - Caused by ______Phototropism
Defined as: the tendency of a plant to grow toward a light source Cool corn - Can be within hours - Caused by changes in auxin concentrations; auxins migrate to shaded tissue, causing elongation of cells Gravitropism Defined as: tendency of shoots to grow upwards (______gravitropism) and roots to grow downwards (______gravitropism)
- Also related to auxin migration - Photoreceptors in shoots determine the light source Arabidopsis Gravitropism Defined as: tendency of shoots to grow upwards (negative gravitropism) and roots to grow downwards (positive gravitropism)
- Also related to auxin migration - Photoreceptors in shoots determine the light source Arabidopsis Gravitropism - ______(cells with starch grains instead of chloroplasts) in roots determine the gravitational pull Gravitropism - Stratoliths (cells with starch grains instead of chloroplasts) in roots determine the gravitational pull Thigmotropism Defined as: ______- Usually found in plants that need structures to wrap around as they grow (vines, climbing plants) - Stems or ______may wrap tightly around objects they encounter to reach light Thigmotropism Defined as: a plant’s response to touch - Usually found in plants that need structures to wrap around as they grow (vines, climbing plants) - Stems or tendrils may wrap tightly around objects they encounter to reach light Nastic Movements
Defined as: a plant’s response to an environmental stimulus ______Example: Venus flytrap, sensitive plant Nastic Movements
Defined as: a plant’s response to an environmental stimulus that does not necessarily take place in the direction of the stimulus Example: Venus flytrap, sensitive plant Response to Seasons
______determines growth and flowering of plants at various times of the year - Phytochrome responsible for ______Response to Seasons
Photoperiod determines growth and flowering of plants at various times of the year - Phytochrome responsible for plants’ photoperiod responses by detecting red light and activating signaling pathways in plant cells 4 Effects of Photoperiod on Flowering: ______: flowers only when exposed to an extended period of darkness (Ex. Poinsettia)
Long-Day Plant: flowers when exposed to a______(Ex. Iris) 4 Effects of Photoperiod on Flowering: Short-Day Plant: flowers only when exposed to an extended period of darkness (Ex. Poinsettia)
Long-Day Plant: flowerswhen exposed to a short period of darkness (Ex. Iris) 4 Effects of Photoperiod on Flowering: ______: flowers when exposed to days & nights of approximately the same length (Ex. cone flower) Day-Neutral Plant: ______(Ex. corn) 4 Effects of Photoperiod on Flowering: Intermediate-Day Plant: flowers when exposed to days & nights of approximately the same length (Ex. cone flower)
Day-Neutral Plant: flowers regardless of day or night length (Ex. corn)