Gaseous Exchange In Plants Flashcards
What is the main photosynthetic organ in most vascular plants
Leaves
What is the site of gaseous exchange
Stomata in the upper and lower epidermis
What is the ground tissue between the upper and lower eoidermis
Medophyll
What type of cell is found in the mesophyll tissue
Parenchyma cells specialized for photosynthesis
Where are stomata mainly found in dicot leaves
In the lower epidermis
What are the two distinct layers found in mesophyll
Palisade
Spongy
Location of palisade mesophyll
The upper part of the leaves just beneath the upper epidermis
What is in the palisade mesophyll tissue
Consist of elongated cells that are arranged in one or more layers
What is the location of spongy mesophyll
Between palisade layer and lower epidermis
How are the cells arranged in spongy mesophyll
Loosely arranged with many air spaces.
Difference in organelle composition between spongy and palisade mesophyll
Palisade mesophyll have more chloroplast
What is the vain arrangement in plants
Highly veined
Net like venation
In which cell layer is the veins found. And how are they protected
In mesophyll layer
Protected by bundle sheath layer
Where are the stomata found in monocot leaves
Both lower and upper epidermis
Features of mesophyll cells in monocot leaves
Not differentiated into palisade and spongy mesophyll
Chloroplast are abundant in all mesophyll cells
Parallel venation
What is a stomata
Stomata are pores surrounded by guard cells in the epidermis of leaves and stems of plants which can open and close
What are gaurd cell
Modified epidermal cells which have a distinct shape
What is the only epidermal cell that contain chloroplasts
Guard cells
What is the typical shape of the guard cells in angiosperms
Bean shaped
What is the structure of the guard cells wall
- Cell walls are unevenly thickened
- Inner cellulose cell wall is thicker and less elastic than outer cells wall
- Some of the cellulose microfibrils are radially arranged to form inelastic hoops around gaurd cells
What is the function of guard cell
Regulate the diameter of stomata by changing shape
Define gaseous exchange
The exchange of gasses between the cells of the organism and the environment
Sites of gaseous exchange in plants
Stomata
Lenticels
Small amount through cuticle
What is the mode of transport for O2 and Co2 within plants
No special system present
Move entirely by diffusion
What is the mode of transport for O2 and Co2 within plants
No special system present
Move entirely by diffusion
What influences the stomatal opening and closing
Change in turgor pressure of the guard cells
Mention how stomata opens
- Water flows into the guard cell by osmosis
- Turgor increases
- Expand non uniformly
- Relatively inelastic inner walls make them bend
- This draws them aways from each other
- Pore opens
How does the stomata close
- Guard cell loses water
- Turgor decreases
- Inner walls straighten
- Pores close
What is the K+ influx hypothesis
During daytime guard cells actively accumulate K+, from neighbouring epidermal cells and lower their water potential that leads to inflow of water by osmosis from surrounding epidermal cells
What provides the energy required for accumulation of K+ in guard cells
The transfer of electrons during photosynthesis of chloroplast in guard cell.
How does stomatal closing occur by loss of K+
loss of K+ from guard cell to neighbouring epidermal cells leads to exosmosis of water. Turgor pressure decrease, closing stomata
What is the acid that plays a role in K+ influx mechanism
Abscisic acid
ABA
What are the roles of ABA in stomatal closing in drought
- ABA is produced in roots and leaves in response to water deficit
- Production of ABA leads to closing of stomata by removal of K+ in guard cells
- This prevents wilting if plants
Factors that affect stomatal action
Light ( stimulate accumulation if K+ in guard cells)
CO2 concentration (decrease=open stomata)
Internal clock of guard cells
Environmental stress like drought, high temperature, wind
