LEAVES (PS 10) Flashcards
State the primary function of leaves
- main area for transpiration- regulate the rate of transpiration and thereby control the transpiration stream and the uptake if water and nutrients
- main area for photosynthesis (production of glucose)
- main area for gas exchange (carbon dioxide and water vapour through diffusion)
Secondary function if leaf-
- propagation
- food and water storage
Describe: Petiole Lamina Veins Midrib
PETIOLE
The stalk of a leaf that joins it to a node on the stem
LAMINA
The blade of the leaf either side of the midrib
VEINS
One of the many lines which can be seen on the surface of a leaf marking the position of the vascular bundles
MIDRIB
The central vein of a leaf
Describe differences between dicotyledons leaf and monocotyledons
Dicotyledons:
- thin flat leaf blades in variety of shape and size
- usually have distinct upper and lower surfaces
- have a network of veins spreading from the midrib that supports the leaf lamina
- most dicots are attached to the to the stem by a petiole
Monocotyledons
- leaves tend to be sword shape
- have no distinct upper and lower surface
- veins are in parallel lines with no distinct midrib
- the leaf surrounds the stem and is attached to the node without a petiole
Describe leaf Arrangement
Leaves are arranged on the stem in a variety of patterns.
OPPOSITE- when each node has a pair of leaves
ALTERNATE - when each node has a single leaf and the adjacent nodes point in different directions
WHORLED - when the node had 3 or more leaves attached.
Describe types of leaf I:e simple, Compound etc
A leaf is referred to as simple if it has a single , undivided blade.
If the blade is divided into several leaflets , then the leaf is compound.
You can distinguish a compound leaf from a simple leaf by looking for lateral buds at the base of the petiole.
SIMPLE
1 petiole + 1 lamina - a single undivided blade
I.e prunus serrula
COMPOUND DIGITATE /COMPOUND LEAF
If the blade is divided into several leaflets then it’s a compound . You can distinguish a compound leaf from a simple leaf by looking fir lateral buds at the base of the petiole.
Aesculus indica
COMPOUND PINNATE
Rosa canina
Draw a dicotyledon leaf section to show the following components: EPIDERMIS XYLEM PHLOEM VEINS PALISADE MESOPHYLL SPONGY MESOPHYLL CUTICLE GUARD CELLS STOMATA
Draw the picture
Describe how leaves have adapted to perform other functions :
Draw a table:
ADAPTION FUNCTION. PLANT NAME
A - SWOLLEN LEAVES
F- To store water
N- Crassula ovata (money plant)
A- TRUE BULB
F- To store food/ carbohydrate
N- Narcissi ‘king Alfred’ ( daffodil)
A- BRACT
F- To attract pollinators
N- Euphorbia pulcherrima (poinsettia)
A - SPINES
F- For protection
N- Ilex Aquifolium ‘Ferox’ - ( holly)
A- LEAF TENDRILS
F- to climb to receive more light
N- Pisum sativum (pea)
A- PROPAGATION
F- to produce off spring
N- Tolmiea menziesii (piggyback plant)
A-CATCHING LEAVES
F- catching food / insects
N- Sarracenia leucophylla (trumpet pitcher)
A- NEEDLES
F- to reduce surface of transpiration
N- Pinus sylvestris (Scots pine)
A- GREY LEAVES
F- to reflect the light
N- Lavandula angustifolia (lavender)
A - HAIRY LEAVES
F-to trap moisture/ water vapour around stomata to increase humidity
N - Stachys byzantina
A- WAXY LEAVES
F- To protect against pathogens
N - Fatsia japonica
Describe EPIDERMIS
In most plants the epidermis is made up of a single layer of cells and it covers the outside surface of the leaf. The cells:
DO NOT CONTAIN CHLOROPHYLL
PRODUCE WAXY LAYER - CUTICLE
CONTAINS BREATHING PORES - STOMATA
( most of which are found on lower epidermis)
CAN PRODUCE HAIRS
Describe CUTICLE
Waxy layer - protection against pest/ disease and infestations and water loss.
Cuticle is transparent and can be very thick depending on plants habitat
Describe palisade layer
Palisade layer / palisade MESOPHYLL
Is a layer of tightly packed OBLONG cells, which contain large number chloroplasts.
Chloroplasts contain the green pigment chlorophyll, which is involved in photosynthesis.
Describe SPONGY MESOPHYLL
LOOSELY PACKED CELLS
they facilitate the diffusion of oxygen, carbon dioxide, and water vapour.
DESCRIBE STOMATA
Stomata are BREATHING pores,
Predominantly in LOWER EPIDERMIS
they alloy for diffusion of gasses into and from the leaf
The size of stomatal aperture is controlled by the GUARD CELLS, these open and close in response to light levels and the water content of the plant
When guard cells are flaccid they close- if turgid they open
Leaf shape
LANCEOLATE
Salix alba
OVAL
camellia sinensis
CORDATE
Tilia cordata
SAGGIATE
Sagittaria latifolia
Leaf margins
ENTIRE
smooth - Cotinus coggygria ‘Flame’
UNDULATE
Fagus sylvatica
SERRATE
Prunus serrula
LOBED
Quercus robur
PARTED
slightly loved with serrated edges
PALMATIFID
Deeper lobed than parted - can be serrated
PINNATIFID
Leaf venation - veins
PINNATE
Has main midrib running through centre with secondary veins coming off
PALMATE/ or DIGITATE
Several mid ribs to which veins branch out of
PARALLEL
Long straight veins - no midrib
