WORKING WITH LEAVES

Eucalyptus macrocarpa leaf and bud

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• LEAF STRUCTURE

Stomates (or stomata) are holes in the under-surface layer that allow water and gas to pass in and out of the leaf.

surface layer of palisade cells

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• NOTE SIZE, SHAPE & TEXTURE

Hardened, with serrated edge and pointed tips

Thick and hardened needle-like leaves with sharp points

Acorn banksia

Cricket ball hakea

Surface with tiny white ‘hairs’, called fibrils

Tar bush

Fibrils on seed pods of Solanum sp.

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LEAVES AND DRYNESS (ARIDITY)

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• HOW A SHEOAK IS ADAPTED TO ARIDITY

• True leaves are reduced to tiny whorls around the stem, with each circlet as a number of tiny leaves (about 0.7 – 1.1 mm long), that curve backwards and overlap each other.

sheoak

Allocasuarina campestris

• Fallen leaves form a dense mat surrounding the base of each tree, a protection against evaporation .

• What appear as leaves are modified stems

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• HOW WATTLES ARE ADAPTED TO ARIDITY

• Not true leaves, instead stems are modified to act as leaves, called phyllodes
• Stems have fewer number of stomates
• Stomates are in sunken pits, and close in severe stress
• Waxy coating

​

Jam tree leaves

Acacia acuminata

Wheatbelt wattles

Stomate, x1000

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OTHER ADAPTATIONS

• Leathery outside layer

• Oil glands in outside layer

Quandong

Wandoo

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• Spines help to stop predation from animals – but maybe not from goats!

• Thick leaves store water

• Silvery surface reflects the Sun’s rays

Insectivorous Sundew

Drosera sp. Photo Kingsley Dixon

Goats in a desert Acacia

• Hairs (fibrils) divert dry air from the leaf surface

• Some leaves have sticky hairs to trap animals for food

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LEAVES MAKE FOOD…

...inside the chloroplast

in the leaf cell

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• IN THE CHLOROPLAST � ENERGY FROM THE SUN � MAKES SUGAR…

2. water

oxygen

1. carbon dioxide

sugar

+

+

…from 2 molecules

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• LET’S MAKE SUGAR

What are molecules?

​

What is the molecular structure of water?

What is the molecular structure of carbon dioxide?

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carbon

oxygen

HH (H₂)

OO (O₂)

oxygen gas

ATOMS

H₂ O

WATER

MOLECULES

COO

CO₂ gas

CARBON DIOXIDE

C

hydrogen gas

O

hydrogen

H

17

Step 1. Make 6 molecules of water

Step 2. Make 6 molecules of carbon dioxide

1.

2.

C

H

H

O O

O

• MAKING SUGAR

Step 4. This leaves one O atom joined with one H atom (OH molecule)

3.

​

4.

H

OH

Step 3. Separate one H atom from the water molecule

Step 5. From the carbon dioxide molecule (made in step 1) separate the C atoms from the two O atoms

5.

C

O

Step 6. Have 5 C atoms and one O atom ready

6.

Step 7. Make a 6-sided ring (hexagon) with 5 C atoms and 1 O atom

7.

O

C

8.

C

O

H

Step 8. Attach 5 H atoms to the 5 C atoms inside the hexagon

22

OH

OH

Step 9. Attach 4 OH molecules (made in step 4) to the outer edge of 4 C atoms

9.

STEP 10.

To the remaining carbon atom (from step 6) add 2 H and 1 OH (from step 4)

STEP 11.

Attach this group of atoms to C atom no. 1

11.

10.

H

OH

C

H

You have made a molecule of sugar!

GLUCOSE

contains energy

12 oxygen atoms, or 6 molecules of O₂ (gas)

What is left over?

6

6 x 2 = 12

how many entered the leaf?

6 + 12 = 18

how many did the leaf use to make sugar?

12

6

how many are left over?

0

remember that the oxygen molecule is 2 atoms bound together

Do your maths!

= 6O₂

O

H

C

6

0

12

Worksheet for equation, 6H₂O + 6CO₂ = C₆H₁₂O₆ + 6O₂

Ben Tisdale, Yrs 4/5/6 Science teacher, Bull Creek PS