Ch 12 Nutrition And Transport In Flowering Plants Flashcards
Definition of photosynthesis?
- Light energy absorbed by chlorophyll
- Light energy -> chemical energy
- Chemical energy used to synthesise glucose from water and CO2
- O2 released in the process
4 layers of the internal structure of a leaf? (Highest to lowest)
- Upper epidermis
- Palisade mesophyll
- Spongy mesophyll
- Lower epidermis
Which parts of the leaf contain chlorophyll?
- Palisade mesophyll
- Spongy mesophyll
- Guard cell
Which 2 layers of the leaf contain chlorophyll?
- Palisade mesophyll
- Spongy mesophyll
Which layer of the leaf contains the most chlorophyll?
Palisade mesophyll
Adaptation: Palisade mesophyll has numerous chloroplasts.
Function?
To trap as much light energy as possible to maximise rate of photosynthesis.
Adaptation: Palisade mesophyll cells are positioned with its longitudinal axis perpendicular to the upper epidermis.
Function?
So that more cells can be packed beneath the epidermis to absorb maximum light energy for photosynthesis.
Adaptation: There are numerous large intercellular air spaces in the spongy mesophyll layer
Function?
Allows higher rate of diffusion of CO2 into the leaf for higher rate of photosynthesis.
Adaptation: Thin film of moisture around palisade and spongy mesophyll cells
Function?
Allows CO2 to dissolve in it.
Adaptation: Numerous stomata on the lower epidermis.
Function?
Open in the presence of light for CO2 to diffuse in.
Adaptation: Veins containing xylem and phloem are located near to the mesophyll cells.
Function?
Xylem transports water to mesophyll cells.
Phloem transports sucrose away from the leaf.
Adaptation: No chloroplast in upper epidermal cells/upper epidermal cells are transparent.
Function?
To allow light rays to penetrate to reach the mesophyll cells for photosynthesis.
What happens to guard cells in sunlight?
- Carry out photosynthesis, produce glucose.
- WP decreases to be lower than surroundings.
- Water enters guard cell.
- Guard cells SWELL and become TURGID.
- Guard cells become CURVED stoma OPENS.
What happens to guard cells on a hot sunny day?
- Leaf loses too much water to the atmosphere?
- Guard cells become FLACCID. Stoma CLOSES.
How does carbon dioxide enter the leaf cells?
- CO2 diffuses into leaf through stomata.
- CO2 dissolves into thin film of moisture around the mesophyll cells.
- CO2 diffuses into cells.
How do the leaf cells receive water and mineral salts?
- Water and mineral salts are transported through the xylem vessels from the roots.
- They move from cell to cell through the mesophyll.
Function of xylem?
- Transport water and mineral salts up from roots to the rest of the plant.
- Provide mechanical support for the plant.
Adaptation of xylem: Hollow tube made of dead cells, w/o cross walls and protoplasm.
Function?
Reduce resistance to the flow of water and mineral salts through the xylem.
Adaptation of xylem: Lignin deposited on its inner walls.
Function?
All the xylem vessels together provide mechanical support for the plant.
Function of phloem?
To transport sucrose and amino acids from the leaves to other parts of the plant.
Adaptation of phloem: Sieve tube cells in the phloem have a thin layer of cytoplasm.
Function?
Allows for rapid flow of manufactured food substances through the sieve tube.
Adaptations of the companion cell in the phloem?
Adaptation 1: Contains many mitochondria.
Provide energy through aerobic respiration, to load sugars from mesophyll cells into sieve tube cell by active transport.
Adaptation 2: Contains ribosomes.
Function: Synthesise proteins required by the sieve tube cell.
Parts of the vascular bundle in the stem and their locations?
Outer: Phloem
Middle: Cambium
Inner: Xylem
Which layer of the leaf is the vascular bundle in?
Spongy mesophyll layer.
*Xylem is nearer to the upper surface of the leaf.