Leaf Anatomy Flashcards Preview

Botany PSC103 > Leaf Anatomy > Flashcards

Flashcards in Leaf Anatomy Deck (15):
1

Basic Leaf Structure?

• Basic leaf structure: • petiole
• lamina/blade
• veins/venation

2

What are the 3 main regions of a leaf?

• 3 main regions
– epidermis
– mesophyll

3

What is the Epidermis?

• Epidermis – transparent, protective layer • many epidermal cell patterns
• most cells have no chloroplasts
• outer wall has a cuticle
• made of cutin (cf lignin & suberin)
• cutin is impervious to H2O & gases
• cuticle v. thin to > 20 microns
• thicker in what environments?

4

What are Trichomes?

• Trichomes (‘hairs’)
• outgrowth of epidermal cell • unicellular & multicellular
• glandular & non-glandular • in arid environments:
– reflect light
– cooler leaf
– decrease water loss

5

What si meant by "Boundary Layer Resistance"?

• Boundary layer resistance
• ‘anything which keeps moist air near the leaf surface for longer reduces transpiration ....’
• trichomes trap still air near the stomata,
• this air becomes more humid,
• reduces diffusion gradient for H2O molecules from intercellular air space (in the leaf) to air

6

What are the Stomata / Stoma?

• Minute pores in epidermis
• Stomata (not stomates) (plural)
• Stoma (not stomate) (sing.)
• ‘most plants’ stomata on lower surface • ‘some plants’ stomata on both surfaces
– in Aust. many genera, e.g. eucalypts
• a few spp. stomata only on upper surface
– eg. spp with floating leaves
• absent in fully submerged lvs
• av. sunflower leaf: 2 x 106 stomata
• each stoma bounded by 2 guard cells • guard cells often join subsidiary cells • guard cells have chloroplasts
• guard cells cell walls
– thickened on side next to pore
– attached to each other at either end – helps in opening/closing
• different monocot & dicot arrangements

7

Remember

• Remember:
• stoma is just the pore or hole • pore + the guard cells =
• stomatal apparatus

8

What are Bulliform Cells?

• Bulliform cells
– large, thin-walled epidermal cells
– in upper epidermis of grasses
– rolling/unrolling of leaves – H20 loss control – See Information Box in the 2nd leaf practical

9

What is the Mesophyll?

Mesophyll (main tissue of a leaf)
• Chlorenchyma – parenchyma with
chloroplasts
• Mesophyll – the chlorenchyma in a leaf
• i.e. chlorenchyma in a leaf is mesophyll
• chlorenchyma in a stem is just chlorenchyma
• Dicots: palisade & spongy mesophyll
• Monocots
– mesophyll usually not divided into palisade/spongy

10

What is the Palisade Mesophyll ?

• Palisade mesophyll
– compact, small dia., columnar
– in leaf TS appears very compact
– in paradermal section see good airspace dev. – upper half of leaf
– usually 2 layers
– often >80% of chloroplasts, thus most

11

What are Spongy Mesophyll?

Spongy mesophyll
– loosely arranged
– large air spaces
– lower half of leaf
– irregular shape
– facilitates gas exchange


12

Explain Kranz Anatomy?

• Kranz anatomy
• found in dicots & monocots
• usually illustrated by monocots
• is associated with C4 PS
• large bundle sheath cells (BSC)
• specialised chloroplasts in BSC, usually next to
mesophyll
• C3 plant BSC cells usually chloroplast free •+
• in C4 the veins are closer together (only 3-4
cells from the BSC of one vein to those of the
next)
• in C4 the mesophyll cells usually radiate out from the BSC

13

Describe Veins (VB's)?

• Veins (VBs)
• X & P surrounded by bundle sheath • Dicots – reticulate veination
– veins cut in TS & lengthwise & at angles – veins of widely differing sizes
– veins different distances apart
• Monocots – parallel veination
– veins cut in TS
– many veins of about the same size – veins equally spaced

14

What are Hydrophytes?

• Hydrophytes
– little Xylem development – large air spaces

15

What is Abscission?

• Abscission
• shedding of plant parts – leaves, fruits, etc • abscission zone – 2 layers
• protective layer
– stem side of petiole
– suberin in cell walls • separation layer