Leaves Flashcards
What are the functions of a leaf?
Photosynthesis, transpiration and gaseous exchange
What is transpiration?
The loss of water vapour by evaporation
What are the external features of a leaf?
Tip, lamina, midrib, margin, vein, base and petiole
What are the 3 different leaf arrangements?
Alternate, opposite and whorled
What does petiolate mean?
The leaf has a petiole ( leaf stalk)
What does sessile mean?
The petiole is absent and the leaf blade attaches directly to the stem
What are the internal structures of a leaf?
Cuticle, upper epidermis, palisade mesophyll cell, bundle sheath cell, xylem, phloem, lower epidermis, spongy mesophyll cells, guard cell, stoma and cuticle
What’s the waxy cuticles function?
Protection and waterproofing
What is the function of the epidermis?
Protection
What is the function of the palisade mesophyll?
For photosynthesis
What is the function of spongy mesophyll?
For photosynthesis and gaseous exchange
What is the function of the guard cells?
To open and close stomata
What is the function of the stomata?
Breathing pores
What are xerophytic adaptations?
Adaptations that allow plants to survive in very dry conditions
Examples of xerophytic adaptations
Small leaves, thick cuticle, leaves held parallel to sun rays and sunken stomata
How do small leaves help plants survive in dry conditions?
Reduced surface area
How does a thick cuticle help plants survive in dry conditions?
Waterproof layer on surface
How do leaves being held parallel to sun rays help plants survive in dry conditions?
Absorb less radiation/ stay cooler
How do sunken stomata help plants survive in dry conditions?
Trap water vapour
Examples of simple leaves
Fagus salvatica, betula pendula and quercus robur
What are monocots leaves like?
Monocots have long narrow leaves with parallel veins or venation
What are dicot leaves like?
Dicots have reticulate veins or venation (branching)
Examples of evergreen leaves
Ilex aquifolium, picea abies and taxus baccata
What happens to deciduous leaves?
First they break down and reabsorb chlorophyll, sometimes leaving autumn colours due to other pigments such as carotenoids and xanthophylls, then they create an abscission layer
What are deciduous?
Deciduous means the leaves are dropped in the autumn as they only stay on the tree for 1 growing season
What happens in evergreen trees?
They can drop leaves in any season but once they are dropped they are replaced
Why are evergreen leaves the way they are?
They live for one to 4 years and have to be able to survive drought and cold so they either have reduced leaves or thick leaves with a thick waxy cuticle
Where is the leaves photosynthetic tissues?
It’s found in the spongy and palisade mesophyll
