Shoot, Architecture & Light Capture Flashcards
Describe the anatomy of typical dicot and monocot leaves
- In most vascular plants, leaves are the main photosynthetic organs
- The exchange of gases occurs through stomata in the upper and lower epidermis
- Epidermis is usually a single cell layer
- In between the upper and lower epidermis, there’s a ground tissue called the mesophyll
- This tissue consists of parenchyma cells specialized for photosynthesis
What are the main photosynthetic organs of most vascular plants?
Leaves
How does the gas exchange of typical monocot and dicot leaves occur?
Stomata in upper and lower epidermis
Where is the mesophyll located?
In-between the upper and lower epidermis
What’s the functions of the cells of the mesophyll?
This tissue consists of parenchyma cells specialized for photosynthesis
Describe dicot leaves
- In dicot leaves, stomata are mainly found in the lower epidermis
- The mesophyll consists of 2 distinct layers of cells called palisade and spongy
- Palisade mesophyll consists of elongated cells arranged in one or more layers. This can be found in the upper part of the leaf, just beneath the upper epidermis
- Spongy mesophyll can be found between the palisade layer and the lower epidermis
- They’re loosely arranged cells with many air spaces
- Spongy mesophyll cells have less chloroplasts than in palisade mesophyll cells
- The vascular tissue of the leaf is continuous with vascular tissue of the stem
- Veins in the leaf are highly branched (net like venation) in the mesophyll layer
- Each vein is protected by a bundle sheath layer
Where are stomata found in dicot leaves?
Mainly on the lower epidermis
Describe the cells present in dicot leaves
- The mesophyll consists of 2 distinct layers of cells called palisade and spongy
- Palisade mesophyll consists of elongated cells arranged in one or more layers. This can be found in the upper part of the leaf, just beneath the upper epidermis
- Spongy mesophyll can be found between the palisade layer and the lower epidermis
- They’re loosely arranged cells with many air spaces
- Spongy mesophyll cells have less chloroplasts than in palisade mesophyll cells
What are the 2 distinct cell layers of the mesophyll?
- Spongy mesophyll
- Palisade mesophyll
What’s the structure of palisade mesophyll?
- Palisade mesophyll consists of elongated cells arranged in one or more layers.
Where are palisade mesophylls found?
in the upper part of the leaf, just beneath the upper epidermis
Where are spongy mesophylls found?
Spongy mesophyll can be found between the palisade layer and the lower epidermis
What’s the structure of spongy mesophylls?
- They’re loosely arranged cells with many air spaces
What’s the vascular tissue of the leaf continuous with?
Vascular tissue of the stem
Describe the vein arrangement in the mesophyll layer of dicot leaves
Veins in the leaf are highly branched (net-like venation) in the mesophyll layer
Each vein is protected by a bundle sheath layer
What is each vein protected by?
A bundle sheath layer
Write the difference between palisade mesophylls and spongy mesophylls
Location: Palisade mesophylls are found in the upper part of the leaf, beneath the upper epidermis. Spongy mesophyll can be found between the palisade layer and the lower epidermis
Structure: Palisade mesophylls consist of elongated cells arranged in one or more layers. Spongy mesophylls are loosely arranged cells with many air spaces
Chloroplast Content: Spongy mesophylls cells have less chloroplasts than palisade mesophyll cells
Describe the structure of monocot leaf
- In monocot leaves, stomata are present in both the lower and upper epidermis
- Mesophyll are not differentiated into palisade and spongy layers
- Chloroplast are abundant in all mesophyll cells
- Vascular tissue of the leaf is continuous with vascular tissue of the stem
- Veins in the leaf are pararally arranged
- Each vein is protected by a bundle sheath layer
Write the functions of each part of the leaf
- Cuticle: Prevents water loss and for Protection
- Epidermis: Protection against pathogens and physical damage
- Stomata: Gaseous exchange and transpiration
- Palisade and Spongy mesophylls: Involving in efficient photosynthesis
- Spongy parenchyma/ air spaces: Photosynthesis and storage of gases
- Vein/ Vascular bundle/ xylem/ phloem: Involving in transport
- Sclerenchyma: Support
- Guard cells: Controlling gaseous exchange and transpiration
Write the differences between dicot and monocot leaf structures
Stomata: In dicot leaves, stomata are mainly found in lower epidermis. In monocot leaves, stomata are present in both the lower and upper epidermis
Mesophylls: In monocot leaves, mesophyll is not differentiated into palisade and spongy. In dicot leaves, there are 2 distinct cell layers called palisade and spongy
Vein arrangement: In dicot leaves, veins are highly branched, with a net like venation in the mesophyll layer. In monocot leaves, veins are parallelly arranged (pararall venation)
Define stomata
Pores surrounded by guard cells which can open and close, found in the epidermis of leaves and stems of plants
Define guard cells
Guard cells are modified epidermal cells which have a distinct shape, and are the only epidermal cells that contain chloroplasts
Describe guard cells
- Guard cells are modified epidermal cells which have a distinct shape, and are the only epidermal cells that contain chloroplasts
- Guard cells are typically bean shaped in angiosperms
- The cell walls of guard cells are unevenly thickened
- The inner cellulose wall is thicker and less elastic than the outer wall
- Some cellulose microfibrils are radially arranged to form inelastic hoops around guard cells
- Guard cells regulate the diameter of stomata by changing shape, widening or narrowing the gap between the pair of guard cells
In angiosperms, what is the shape of guard cells?
Typically bean shaped
