2.5 Leaves Flashcards Preview

RHS Level 2 Module R2101 > 2.5 Leaves > Flashcards

Flashcards in 2.5 Leaves Deck (23)
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1

What is the primary function of a leaf?

Photosynthesis

2

What is the petiole?

Stalk (midrib minus the tissue!)

3

What is the lamina?

Simple leaf blade

4

Describe the veins?

Midrib is central vein, and secondary veins branch off that.

5

What is the midrib?

The central vein in a leaf

6

Simple leaf shapes? (4)

Lanceolate (spearhead shape)

Ovate (egg shape)

Linear (grasses)

Palmate (acers etc)

7

How does leaf colour vary?

Varies according to pigment in leaves

Chlorophyll breaks down over time - light green goes to darker, and then red/browns etc.

Variegated leaves are mixture of yellow (non-photosynthetic) and green (photosynthetic)

Some have red undersides - reflects sun's rays back into leaf. Good for forest floor plants!

8

Leaf arrangements on stems? (3)

Alternate

Opposite

Whorled

9

How are leaves adapted to form other functions? (8)

Optimal photosynthesis

Climbing

Preventing water loss

Encouraging water loss

Defence

Storage

Reproduction

Carnivory

10

What does the mesophyll layer in a leaf do?

The palisade mesophyll is the main site of photosynthesis.

The spongy mesophyll is also site of photosynthesis. Air spaces facilitate gas exchange and store CO2. Cells may also store starch.

11

What are compound leaf shapes? (2 examples)

These are simple leaves divided into "leaflets"

Pinnate compound - leaflets are arranged along a midrib

Palmate compound - leaflets are attached at a common point.

12

How do leaves adapt for optimal photosynthesis?

Arranged in patterns to catch maximum sunlight

Lamina tracks the sun via pulvinus at base of petiole

Pulvinus allows Oxalis leaves to collapse at night

13

How do leaves adapt for climbing?

Leaves wrap around supports or other plants

Tendrils cling to surroundings

14

How do leaves adapt for reproduction?

Some species produce tiny plantlets on leaf margins

15

How do leaves adapt to prevent water loss?

Mediterranean/coastal/"cold" deserts etc:

Thick, silky hairs on leaf surface catch moisture

Thick, waxy coatings prevent evaporation

Needle-like leaves roll in to reduce surface area to drying winds

Pores are on underside of leaf (so inside rolled "needle")

16

How do leaves adapt to encourage water loss?

Attenuate leaves channel water off leaves (drip tips) - tropical rainforests etc.

(this prevents water logging to allow efficient photosynthesis, and prevent fungal infection)

17

How do leaves adapt for defence?

Spiny leaves

Stinging hairs

Variegation (camouflage)

Strong colour on midrib and veins (to mimic toxic ferns)

18

How do leaves adapt for storage?

Bulbs are modified, underground leaves - swell up and store nutrients. (Plants survive harsh conditions underground)

Outer leaves dry off and act as protection (onion)

Vegetative reproduction (bulblets form underground)

19

How do leaves adapt for carnivory?

In low nitrogen areas this is a backup!

Modified leaves that catch insects for protein

Pitcher plants have a soup of enzymes

Sundews and butterworts have sticky, sugary leaves

20

What is the function of stomata?

Site of entry of carbon dioxide and release of oxygen (gas exchange) and transpirational water vapour loss.

21

What is the function of the cuticle?

Waterproofing waxy layer which reduces water loss and protects from pest and disease damage.

22

What is the function of guard cells?

Control the opening and closing of the stoma and control water loss.

23

Describe FOUR leaf adaptations:

Leaf spine - for defence or protection

Succulent or fleshy leaves - to store water

Bulb - starch storage or perennation

Needles - to reduce water loss