Biology C-3 Flashcards
Photosynthesis
Conversion of light energy from the sun to chemical energy stored in sugar and other organic molecules
-Occurs in Chloroplast
Root System
Organ- Roots
Function- Anchors plants to soil, absorbs minerals + water and stored carbohydrates
Shoot System
Organs- Stems and Leaves
Function- Absorbs CO2 and light from above the ground
-Stem: Supports leaves and reproductive structures
-Leaves: Photosynthetic organ
Tissues
Dermal- Outer protective covering
Vascular- Carriers out long distance transport of materials between root and shoot system
Ground- Storage, photosynthesis and support
Cuticle
Tissue Type- Dermal
Function- Waxy substance that costs epidermal cells. Helps prevent water loss
Upper Epidermis
Tissue Type- Dermal
Function- A one cell thick, layer of tightly packed transparent cells on upper side of leaf that protects against mechanical damage and pathogens
Palisade
Tissue Type- Ground
Function- One or more layers of tightly packed long narrow cells with many chloroplasts. Where most photosynthesis occurs
Vascular Bundle
Tissue Type- Vascular
Function- Series of tubes visible as leaf veins. Contain xylem and phloem that transport fluids
Xylem
Tissue Type- Vascular
Function- Tubular elongated cells that are dead. Transports water upward from roots to leaves
Phloem
Tissue Type- Vascular
Function- Long narrow cells that are alive. Transports sugars produced by the leaves to various parts of the plant where they are needed
Lower Epidermis
Tissue Type- Dermal
Function- A one cell thick, layer of tightly packed transparent cells on lower side of leaf that protects against mechanical damage and pathogens
Spongy Tissue
Tissue Type- Ground
Function- Layers of round loosely packed cells containing chloroplasts, Located below palisade tissue cells. Carry out photosynthesis. Air space in between all for gas transport
Stomata
Tissue Type- Dermal
Function- Small openings in epidermal layer that open and close to allow gas in and out of the leaf. Each stomatal pore is flanked by two guard cells that control diameter of stoma by changing shape
Absorption by roots and transport to xylem
Active transport of minerals into the roots causes water to move into the roots by osmosis
- Root hairs increase SA
Bulk Transport - Root pressure
Accumulation of water in root xylem that pushes sap up stem towards the leaves (minor mechanism)
Bulk Transport - Cohesion
Tendency of water molecules to stick to other water molecules
-Pulls a column of water up to leaves
Bulk Transport - Adhesion
Tendency of water molecules to stick to certain surfaces
-prevents sap from falling back down (resist’s gravity)
Sugar Transport
Loading of Sugar- Sugars produced by sugar source are transported to phloem vessel by active transport
Uptake of water- Osmosis causes water to move into the phloem vessel increasing pressure inside the vessel
Bulk transport- Pressure and concentration gradients move the phloem sap toward the sugar sink
Unloading of sugar- Increasing pressure forces the phloem sap out the vessel into neighbouring cells
Gas Exchange (Leaves)
Most gas exchange occurs through stomata in epidermal layer
- CO2 is transported into leaf and O2 is transported out through passive transport
Gas Exchange (Stems and Roots)
Lenticles- Lense shaped opening in bark of woody plants that enable gas exchange
Transpiration
Loss of water through diffusion and evaporation
- Large sa, High sa/v ratio and stomata important for photosynthesis but also increase water loss
Controlling stomata
Open- In moist environments, guard cells open all
-Gain water, become turgid and open
Close- In dry environments, guard cells close
-Lose water, become flaccid and close
Tropism
Any growth response that results in plant organs curving toward or away from stimuli
- Positive Tropism - Growth toward the stimulus
- Negative Tropism - Growth away from the stimulus
Phototropism
Growth toward or away from light
Phototropism - Darwin and Darwin
Problem: What part of the plant senses where light is coming from?
Results:
- Tip removed - No phototropism
- Tip covered by opaque cap - No phototropism
- Tip covered by transparent cap - Positive phototropism
- Stem covered by opaque shield - Positive phototropism
Conclusion: The tip of the seedling detects light and sends a signal down to the stem to control growth
Phototropism - Boysen-Jensen
Problem: What type of signal controls stem growth
Method: Tip separated from stem by different barriers
Results:
- Gelatin (permeable) - Positive phototropism
- Mica (impermeable) - No phototropism
Conclusion: The signal is a mobile chemical because it passes through the gelatin (permeable barrier), but not the mica (impermeable barrier)
Frits Went
Problem: What is the chemical signal
Method:
- Removed the seedling tip and placed it on an agar block to allow the chemical messenger to diffuse into the agar
- Agar block placed on different parts of the decapitated stem in the dark
Results:
- Centered - Grew straight
- Off-centered - Curved away from the side with the agar block
Conclusion: Auxin is the chemical messenger, hormone, that causes elongation of the cells on the darker side
Gravitropism
Growth in response to gravity
-Roots display positive gravitropism
-Stems display negative gravitropism
