2101 - Leaves Flashcards Preview

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Flashcards in 2101 - Leaves Deck (20)
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1
Q

Main Functions of a Leaf

A

Provide a site for Photosynthesis.
Regulate Transpiration.
Allow Gaseous Exchange.

Arrise from Nodes on the stem as it grows. Do not arrive from anywhere else.

2
Q

Physiological Functions

A

Convert Light, CO2 and H2O into sugars via Photosynthesis.

Regulate Transpiration, thus the uptake of water and nutrients by the plant.

Control the absorption and release of CO2 and O2 via Gaseous Exchange.

3
Q

Leaf parts

A
Axially bud (on stem)
Petiole (stalk)
Leaf Base
Lamina (leaf blade)
Margin (the edge)
Midrib (main vein)
Lateral Veins
Sub Lateral Veins
4
Q

Leaf Characterisation

A
Shape
Size
Colour
Margin
Venation
Division of the Leaf Blade
Arrangement on the Stem
5
Q

Internal Structure of a Leaf

A
Cuticle
Upper Epidermis
Pallisade Mesophyl
Spongy Mesophyl
Lower Epidermis
Stomata
Sub-Stomatal Air Chamber
Guard Cells
6
Q

Internal Structure of a Leaf - Epidermis

A

Single layer of cells, do not contain chlorophyll, but produce Waxy layer cuticle.
Lower epidermis contains the stomata.
Relatively transparent.

7
Q

Internal Structure of a Leaf - Cuticle

A

Waxy layer protects against pests, disease and water loss.

Can be thick or thin depending on the plant.

8
Q

Internal Structure of a Leaf - Palisade Mesophyll

A

Tightly packed oblong/vertically arranged cells just under the upper epidermis.
Large number of Chloroplasts for optimum Photostynthesis.

9
Q

Internal Structure of a Leaf - Spongy Mesophyll

A

Parenchyma cells below the Palisade cells.
Typically less Chloroplasts than Palisade cells.
Loosely packed to facilitate the diffusion of Oxygen, Carbon Dioxide and water vapour.

10
Q

Internal Structure of a Leaf - Stomata

A

Breathing pores predominantly in the lower epidermis in Dicots. Allow for Gaseous exchange.

Controlled by Guard Cells in response to light levels and water content of the plant.
Under Active and Passive control.

Ions can be pumped into and out of the guard cells causing them to lose or gain water (osmosis) and open or close.

Water loss by dehydration (loss of Turgor) can also close the stomata. Inhibiting gaseous exchange therefore further water loss via Transpiration.

11
Q

Leaf Arrangement on Stem - Opposite, Alternate, Whorled.

A

Opposite - Each node has a pair of leaves.
Cornus spp.

Alternate - Each node has a single leaf, the adjacent nodes point in different directions.
Salix spp.

Whorled - Node has three or more leaves.
Galium spp.

12
Q

Leaf Arrangement - Simple vs Compound

A

Simple - Single undivided blade or Lamina. Cannot be sub-divided into leaflets.
May be formed of lobes (Quercus) but gaps do not reach the Mid Rib.

Compound - Blade is divided into several leaflets. Identified by the lack of Axially bud. (Midrib may be called Rachis)

13
Q

Simple, Lobed, Palmately Compound, Pinnately Compound

A

Simple - Fagus syllabic
Lobed - Quercus roubar
Palmate - Aesculus hippocastanum
Pinnate - Fraxinus excelsior

14
Q

Leaf Adaptions

A
Tendril
Spines
Water Storage
Carnivorous
Perennation
15
Q

Leaf Adaptions - Tendril

A

Climbing by Tendril, modified leaflet.
Support and height to increase availability of Light, Air and chance of Pollination.

Pisum sativum (Garden Pea)

16
Q

Leaf Adaptions - Twining Petioles

A

Clematis spp.

17
Q

Leaf Adaptions - Spines

A

Modified leaves for protection from predators.

Berberis thunbergii

18
Q

Leaf Adaptions - Water Storage

A

Succulent fleshy leaves for water storage.

Hylotelephium ‘Herbstfreud’

19
Q

Leaf Adaptions - Carnivorous

A

Venus Fly Trap, to ensure nutrients in short supply for the plants situation.

Dionaea muscipula

20
Q

Leaf Adaptions - Perennation

A

Bulb, modified scale leaves. Used for food and water storage for next seasons growth.

Narcissus pseudonarcissus