Gas Exchange Plants Flashcards
(13 cards)
How is gas exchanged used in plants?
In light: both photosynthesis and respiration
In dark: just respiration
Both respiration and photosynthesis require gas exchange
What are the first 7 layers of plant?
- Cuticle
- Upper epidermis
- Palisade mesophyl
- Air spaces
- Bundle sheath
- Xylem
- Phloem
What are other 4 layerz?
- Spongy mesophyl
- Stomata
- Guard cells
- Lower epidermis
What are 4 adaptions of lead for gas exchange?
- Thin and flat for large surface area
- Large air spaces in spongy mesophyll allowing the circulation of gases
- Small air spaces between cells of other tissues
- Stomata present and can open for gas exchange
What is pathway of gases into cells?
- Gases diffuse through stomata down omcincentration gradient
- Then gases diffuse through intercellular spaces between mesophyll cells.
- Gasses diffuse into film of water covering cells and in the cellulose cell war
- Then gas diffuses into cell
What direction do gasss move in light and dark?
Light: CO2 in, O2 out
Photosynthesis dominant but respiration still happens
CO2 prod. respiration used, but more needed
Some oxygen used for respiration but most diffuses out
Dark: O2 in, CO2 out
Respiration dominant, no photosynthesis
What are leaf adaptions for light absorption
- Leafs have large surface area to capture as much light as possible
- Leaves can move (slowly) so they are held in the position which helps to gather most light
- Cuticle and epidermis are transparent to allow light to reach mesophyll cells (where chloroplasts are)
- Leafs are thin to allow light to reach lower layers of leaf.
What are adaptions of palisade cells?
Elongated,
densely packed,
have small air spaces between them
Contain many chloroplast
Chloroplasts can move in cells to collect the most light or move away from strong light to avoid damage.
What are adaptions of the cuticle?
- secreted by epidermal cells in epidermis
- waxy, as waterproofing agent, reducing water loss from epidermis (thicker cuticle = less loss)
- covers upper and lower epidermis (besides stomata)
- in preventing water loss, also prevents gas exchange
- stomata allows water and gas through
What are adaptions of guard cells?
- guard cells are in epidermis and can change shape to form stoma for gas exchange
- guard cells, unlike epidermal cells, have chloroplasts.
-stoma vary in how much they open - when closed, gas exchange + water loss reduces, vice versa
What is turgor of guard cells?
- guard cells can change shape to open/close stoma
- when water flows into guard cells they become turgid and curve away from each other
- as inner wall is thicker and inelastic compared to outer
- when water flows out, cells become less turgid and walls meet again, closing stomata
How does stomata open
- Photosynthesis takes place in precedence of light, producing ATP
- ATP allows active transport of K+ ions into the guard cells.
- Starch is converted to malate
- Water potential in guard cells is lowered.
- Water moves into cells by osmosis
- Cells become turgid and elongate on outer edge of cell.
- Inner edge is thicker and less flexible, so stomata opens.
How does stomata close?
- K+ ions leave guard cells via facilitated diffusion (less ATP because less photosynthesis in dark)
- Malate converted to starch
- Water potential raised.
- So water leaves gayes cell via osmosis down water potential gradient
- Cells become plasmolysed and stoma closes
