AP Biology Plant Control and Coordination
1. What is the effect of the plant hormone ethylene on fruit ripening? 2. How does fruit change as it ripens? 3. What is the mechanism behind ripening? 4. Why does fruit ripen faster if placed in a paper bag?
Simplified Carbon-Cycle 1. Which arrow (I or II) is photosynthesis? Which is respiration? 2. When a plant grows and gains mass, where does that mass come from? 3. What would happen to a plant s mass if it was kept in the dark for two days? What chemical reaction is responsible? Where would the mass go?
Predict how the following treatments would affect the rate of germination? Justify each prediction: 1. Temperature: cold, warm, boiling 2. Environment with/without oxygen 3. Environment with/without light
How Plants Detect Light Plant tissues contain a pigment called phytochrome that absorbs red light It serves to judge the quality of light Low levels of red-light indicates competition for light Plant will invest in growing taller (getting into or above canopy) Once in full light, vertical growth inhibited and branching can begin
1. Which colors of visible light are absorbed by the chlorophylls (a & b) during photosynthesis? 2. Why are most plant leaves green?
1. In terms of lightcompetition, what is the difference between the two seedlings? 2. How do the seedlings sense lightcompetition? 3. Predict how the growth form of the two plants will differ and explain why:
Plants can detect: presence of light, its direction, intensity, and wavelength (color) Red and blue light are the most important colors for driving photomorphogenesis (plant growth and development)
Responses to Light are Crucial to Plant Success Light triggers many key events in plant growth & development - photomorphogensis No chlorophyll or leaves Energy allocated to elongating its stems to break above ground Stem-elongation slows Leaves expand (green) Roots elongate
Tropism = any growth response that results in plant organs curving toward or away from stimuli Positive = toward a stimulus Negative = away from a stimulus Phototropism = movement of plant towards the source of light (wavelength/color)
Photoreceptors in Plants Which wavelengths induce stem-tip curvature? Blue-light photoreceptors absorb blue-light
Make a claim with justification for which part of the plant is required for a plant to sense light and react by phototropism:
1. How do the length of the cells on the shaded and illuilluminated sides compare? 2. Explain how this differential growth results in curvature:
A higher [ ] of the plant hormone auxin, through a signal-transduction pathway, results in elongation of cells
Photoperiod & Photoperiodism Long-night Short-night Photoperiod the relative lengths of night and day Used by plants to detect time of year A physiological response to photoperiod is called photoperiodism Example: when to flower
Short-day (long-night) plant 1. Describe the relative amount of light and dark that is required to trigger a shortday/long-night plant to flower? 2. How do shortday/long-night plants react to a flash of light that punctuates the long period of darkness?
Is it more accurate to refer to plants as short vs. long-day or short vs. longnight? Why?
Long-day (short-night) plant 1. Describe the relative amount of light and dark that is required to trigger a long-day/short-night plant to flower? 2. How do long-day/shortnight plants react to a flash of light that punctuates the long period of darkness?
Signaling Molecule for Flowering A protein, florigen, is transcribed from a gene called flowering locus (FT) It is activated in leaf cells that are exposed to the amount of light/dark that is favorable to flowering in that species Florigen travels from the leaf to the bud and activates transcription of other genes that are required for the development of a flower
1. How has the date of first bloom changed from 1850 to 2000? 2. What type of data is this trend based on?
Environmental Energy Mismatch What affect do you think global warming will have on: a. Bird population b. Caterpillar population c. Oak Population Feeds on oak
Environmental Energy Mismatch Case-study Caribou migration triggered by day-length temp. has sped up plant sprouting in the spring Now plant nutrition and digestibility have peaked before the arrival of caribou There is a mismatch in timing between new plant growth and caribou birthing Without adequate nutrition for nursing, production of offspring has declined 75% since 1993