Investigating Water Conserving Structures in a Range of Terrestrial Australian Plant
Specimens
Aim:

- To make observations and draw water conserving structures present in various
Australian xerophytic plants and to relate these structures to their functions.
Hypothesis:
It is believed that a range of xerophytic Australian plants will demonstrate water conserving structures such as rolling of the leaves, thin and long leaves, thick layer of cuticle, hairy leaves, small leaves and flowers, sunken stomates and swollen stem to adapt to their arid environment. Materials:
• Leaves, stems, flowers and fruits of Casuarina, Eucalyptus, Cactus, Acacia, Hakea,
Spinefex, and Banksia
• Internet and BIF textbook images/drawings or prepared glass slides of xerophytes
• Stereo microscope
• Compound Optical Microscope
• Glass slides
• cover slips
• mounting needle
• forceps
• magnifying glasses or hand lens
Risk Assessments:

- Extra care is needed when handling microscopes and the prepared glass slides as
-

breakages might occur. Place the microscope and glass slides away from the edges of the table to avoid them from falling.
When handling the different types of xerophytic plants, make sure they are away from eyes, nose and face as allergies or skin irritation to plants may occur if inhaled or held for too long, always wear apron or gloves if necessary.

Method:
1. Observe and draw the leaves of the xerophytic plants
2. Noticing their distinctive features including the leaves, stem flowers and fruits.
3. Use a compound microscope, magnifying lens or stereo microscope to observe the positions of the stomates, presence of hair and mid vein on the leaves and other distinctive features of the specimens.
4. Use the internet for secondary sources and BIF for prepared images and compare results 5. Record observations of the specimens in a table
Results:
Specimen:

Adaptive Features that Minimise Water Loss:

Eucalyptus

Leaves:
• waxy cuticle - water proof and reflects sunlight, distributed stomates
• orientation of the leaves - vertically down to reduce surface area from sunlight Specimen:

Adaptive Features that Minimise Water Loss:

Cactus

Leaves:
• reduced to spines - less evaporation from stomates
Stem:
• swollen stem - storage of water

Acacia

Flowers:
• small flowers - require less water to produce

Hakea

Leaves:
• divided leaves - reduced size, less evaporation for the stomates
• curled leaves - sunken stomates to reduce water loss from evaporation

Spinefex

Leaves:
• curled leaves - sunken stomates to reduce water loss from evaporation

Banksia

Leaves:
• waxy cuticle - water proof and reflects sunlight, distributed stomates
Flowers/Stem:
• hairy flowers and stem - conserve water around area of leaves
(humidity)
• woody fruits - reduce water loss from evaporation

Discussion:
This experiment is reliable as we have used first and second hand resources in conducting this report. The level of accuracy of this experiment was also high as we have used actual specimens to study and have used updated secondary resources to compare our results.
We have not only examined the different adaptive features of individual plants but also compared them with each other. An improvement to this experiment is to change the method using secondary sources conducted in a non-destructive manner also by studying the plants in their natural environment using hand lenses or a stereomicroscope. It was difficult for this experiment to be conducted in that way because we did not have a garden to supply specimens which is why they had to be bought. An alternative to this improvement was then made by using prepared slides or secondary sources such as images or photomicrographs of the specimens. Some difficulties encountered form this experiment was to identify the structures and adaptations of xerophytic plants to confirm the true leaves from modified leaves (cladode or phyllodes). An improvement made was to make transverse sections of the leaves then studied under light microscope. This would show whether it is a true leaf or not because true leaves have a mid-vein, chlorophyll and a shiny cuticle unlike modified leaves which have neither.
Conclusion:
In conclusion, adaptive features of water conserving structures were present in various
Australian xerophytic plants. Most of the specimens examined, as shown in the results, have similar special adaptations such as rolling of the leaves, thin and long leaves, thick layer of cuticle, hairy leaves, small flowers, sunken stomates and swollen stem. These adaptive features all result in reducing water gradient from evaporation in the stomates, and exposure from the sunlight thus decreasing the rate of transpiration of the plants.