plants Flashcards
(18 cards)
What are the main problems of living on land for plants?
Support-maximise light capture and gas exchange
Avoid desiccation, but acquire CO2
Acquire nutrients
These challenges require various adaptations for survival.
What adaptations do leaves of plants growing in high light levels exhibit?
- Longer and/or more palisade cells
- Increased Specific Leaf Area
- More RUBISCO, but less chlorophyll per unit leaf weight
- Increased leaf area index
These adaptations enhance photosynthesis efficiency in bright environments.
What is essential for C3 plants to maintain in their chloroplasts?
High CO2 concentration
This is crucial for optimizing photosynthesis.
Describe the characteristics of leaves in full sun for C3 plants.
- Thicker
- More mesophyll surfaces occupied by chloroplasts
- Secure area for CO2 dissolution and transport
- Maintain high CO2 concentration
These adaptations help maximize photosynthesis in bright conditions.
What are the characteristics of shaded leaves in C3 plants?
- Thinner
- More chlorophyll per unit weight
- More thylakoids in grana
These features enhance light capture in low-light environments.
What are the effects of high CO2 concentration on C3 plants?
- Longer and/or more palisade cells
- Increased specific leaf area
- Reduced stomatal density
- Increased water use efficiency
High CO2 conditions promote growth and efficiency.
What is the primary carboxylation enzyme in C4 plants?
Phosphoenolpyruvate Carboxylase (PEPc)
PEPc operates efficiently at lower CO2 concentrations compared to RUBISCO.
What is the ecological importance of C4 photosynthesis?
- Important for grazing mammals
- Implicated in human development from forest to grassland species
C4 photosynthesis contributes to ecosystems and evolutionary changes.
What is CAM photosynthesis?
Crassulacean acid metabolism - fix carbon with PEPc at night
This adaptation allows plants to survive in low-water environments.
How do CAM plants manage water availability?
- Close stomata during the day
- Open stomata at night
- Fix CO2 and store it as a four-carbon acid (malate)
This strategy minimizes water loss while allowing photosynthesis.
What is the role of meristems in plants?
Cells undergoing mitotic cell division (growth)
Meristems are crucial for plant development and growth.
What are the primary meristems formed during embryo development?
- Shoot apical meristem (SAM)
- Root apical meristem (RAM)
These meristems give rise to various plant organs.
What is determination in plant development?
The process by which undifferentiated cells become committed to develop into specific cell types
This is crucial for organ development.
What is a leaf?
- Lateral outgrowths of a plant shoot
- Vascularized in vascular plants
- Usually photosynthetic
- Short-lived organs
Leaves are essential for photosynthesis and plant growth.
What distinguishes microphylls from megaphylls?
Microphyll: one vascular bundle, no complex network of veins
Megaphyll: several large veins, connected by a network of smaller veins
This distinction is important in plant taxonomy.
What percentage of vascular plants are CAM?
About 6%
CAM is relatively rare among vascular plants.
What is the significance of aquatic CAM?
- Dominant in acidic pools with low CO2 availability
- Avoids competition with algae and other plants fixing carbon during the day
This adaptation allows CAM plants to thrive in specific environments.
What are the functions of leaves?
- Photosynthesis
- Spore bearing (in ferns)
- Defence
- Support
- Structural modification in response to environmental constraints
Leaves serve multiple critical functions in plant survival.
