Tropisms, , & Photoperiods Growth & Development Defined as: ______3 Types: - - ______- Tropisms Defined as: Plant growth responses to environmental stimuli that occur in the direction of the stimuli 3 Types: - Phototropism - - 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 concentrations; migrate to shaded tissue, causing elongation of cells Gravitropism Defined as: tendency of shoots to grow upwards (______gravitropism) and 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 ) 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 that need structures to wrap around as they grow (, 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 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 - 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)