Podcast
Questions and Answers
What is the purpose of the coleoptile in grass seedlings?
What is the purpose of the coleoptile in grass seedlings?
- To protect the growing shoot (correct)
- To store energy for the plant
- To facilitate water uptake
- To absorb nutrients from the soil
What results from unequal light perception in the coleoptile?
What results from unequal light perception in the coleoptile?
- Balanced growth on all sides
- Uniform bending of the coleoptile
- Unequal concentrations of auxin (correct)
- Complete cessation of growth
What causes phototropic bending in coleoptiles?
What causes phototropic bending in coleoptiles?
- Growing organs perceiving unilateral light (correct)
- Temperature fluctuations
- Presence of nutrients
- Exposure to soil moisture
When does a coleoptile stop growing?
When does a coleoptile stop growing?
Which statement about the growth of coleoptiles is true?
Which statement about the growth of coleoptiles is true?
What triggers unequal growth in the coleoptile?
What triggers unequal growth in the coleoptile?
How do coleoptiles respond to sunlight?
How do coleoptiles respond to sunlight?
What happens to coleoptiles and shoots that have stopped elongating when exposed to unilateral light?
What happens to coleoptiles and shoots that have stopped elongating when exposed to unilateral light?
What factor most closely regulates stomatal opening in Vicia faba according to the data provided?
What factor most closely regulates stomatal opening in Vicia faba according to the data provided?
At what time of day is stomatal aperture most likely to be affected by blue light?
At what time of day is stomatal aperture most likely to be affected by blue light?
Which type of light is related to stomatal movements in the provided data?
Which type of light is related to stomatal movements in the provided data?
What happens to protoplasts when exposed to blue light?
What happens to protoplasts when exposed to blue light?
What element of light was indicated as a dominant response for stomatal opening?
What element of light was indicated as a dominant response for stomatal opening?
In which experimental condition is the stomatal pore measured?
In which experimental condition is the stomatal pore measured?
What is the unit of measurement for stomatal aperture provided in the data?
What is the unit of measurement for stomatal aperture provided in the data?
Which statement is correct regarding stomatal pore changes over the day?
Which statement is correct regarding stomatal pore changes over the day?
What is the role of cryptochromes in plants?
What is the role of cryptochromes in plants?
What is characteristic of the hy4 mutant of Arabidopsis?
What is characteristic of the hy4 mutant of Arabidopsis?
Which light condition is associated with the hy4 mutant's phenotypic expression?
Which light condition is associated with the hy4 mutant's phenotypic expression?
What effect do cryptochromes have on hypocotyl elongation in normal plants?
What effect do cryptochromes have on hypocotyl elongation in normal plants?
In which plant species is the hy4 mutant observed?
In which plant species is the hy4 mutant observed?
What is one of the metabolic pathways that supply osmotically active solutes to guard cells?
What is one of the metabolic pathways that supply osmotically active solutes to guard cells?
Which compound has been proposed as the chromophore of a blue-light photoreceptor in stomatal guard cells?
Which compound has been proposed as the chromophore of a blue-light photoreceptor in stomatal guard cells?
What is the outcome of the identification of mutants for key blue-light responses?
What is the outcome of the identification of mutants for key blue-light responses?
What role do K+ and Cl– play in the metabolic pathways for guard cells?
What role do K+ and Cl– play in the metabolic pathways for guard cells?
Which process occurs during the production of sucrose in guard cells?
Which process occurs during the production of sucrose in guard cells?
What remains to be established regarding the blue-light photoreceptor in guard cells?
What remains to be established regarding the blue-light photoreceptor in guard cells?
What process in guard cell chloroplasts is responsible for producing sucrose?
What process in guard cell chloroplasts is responsible for producing sucrose?
Which of the following is NOT a source of osmotically active solutes in guard cells?
Which of the following is NOT a source of osmotically active solutes in guard cells?
What is the main cell type responsible for blue light-dependent stomatal movements?
What is the main cell type responsible for blue light-dependent stomatal movements?
How does the stomatal response to blue light differ from phototropism?
How does the stomatal response to blue light differ from phototropism?
What characteristic of blue light–dependent stomatal movements makes it suitable for experimental studies?
What characteristic of blue light–dependent stomatal movements makes it suitable for experimental studies?
Which physiological process is NOT mentioned as being functionally important at early stages of plant development?
Which physiological process is NOT mentioned as being functionally important at early stages of plant development?
What does the signal transduction cascade associated with blue light regulation involve?
What does the signal transduction cascade associated with blue light regulation involve?
What does the rapidity of the stomatal response to blue light indicate?
What does the rapidity of the stomatal response to blue light indicate?
Which statement is true regarding the regulation of stomatal movements by blue light?
Which statement is true regarding the regulation of stomatal movements by blue light?
The characteristic of blue light response in stomata enables what specific feature?
The characteristic of blue light response in stomata enables what specific feature?
Study Notes
Coleoptile Growth and Phototropism
- Grass shoots are protected by a coleoptile, a modified leaf.
- Unequal light perception in the coleoptile leads to uneven auxin distribution, causing it to bend (phototropism).
- Phototropic bending only occurs in actively growing organs; it ceases once the shoot emerges from the soil.
Stomatal Movements and Blue Light
- Stomatal movements are a valuable model for studying blue light responses.
- The stomatal response to blue light is rapid, reversible, and localized to guard cells.
- This response regulates stomatal movements throughout the plant's life, unlike phototropism or hypocotyl elongation which are primarily important in early development.
- Stomatal opening in Vicia faba closely follows photosynthetically active radiation (400-700 nm).
- Four metabolic pathways supply osmotically active solutes to guard cells: K+ and Cl- uptake coupled with malate2- biosynthesis; sucrose production from starch hydrolysis; sucrose production via photosynthetic carbon fixation in guard cell chloroplasts.
Blue Light, Stomatal Aperture, and Time of Day
- Figure 18.10 shows the response of stomata to blue light under a red-light background.
- Stomatal aperture increases significantly with blue light exposure.
Blue Light Responses and Gene Identification
- Research on blue-light responses, such as phototropism and stem elongation inhibition, involved identifying mutants and isolating relevant genes.
- Gene cloning led to identifying and characterizing encoded proteins, important for elucidating mechanisms.
Cryptochromes and Hypocotyl Elongation
- The hy4 mutant of Arabidopsis lacks blue-light stimulated inhibition of hypocotyl elongation.
- hy4 plants exhibit elongated hypocotyls under blue light due to the genetic defect.
- Zeaxanthin is a proposed chromophore for a blue-light photoreceptor in stomatal guard cells, but the apoprotein remains unidentified.
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Description
Explore the fascinating mechanisms of coleoptile growth and phototropism, as well as the role of blue light in regulating stomatal movements. Understand how auxiliary factors like auxin distribution and metabolic pathways influence plant development. This quiz will challenge your knowledge of plant physiological responses to light.
