Design a Tree Model of Water Transport

Materials:

These will depend on your design, but at least some kind of tube (e.g. cardboard, plastic drinking straws, etc.) will be required.

Method:

1. Brainstorm/Discuss/Write: Role of Water in Plants

• Estimate the height of the tallest trees you have seen.

• What role(s) does water play in plants?

• If trees are the tallest living things on earth, how do they manage to conduct water from the ground to this great height, against the force of gravity and without the benefit of any contracting, muscular tissues such as animals use to circulate body fluids? (The limit of a human-made suction pump is 10 m and that trees can grow 10 times this height!)

2. Design a model tree showing the water transportation system.

• Use your own imagination and understanding of how trees absorb and transport water.

• Keep track of the materials that you will require for building the models and plan ways for obtaining them.

• Remember that plants are not outfitted with technological gadgetry; pumps that raise water against the force of gravity are physical processes different from those at work in transpiration.

• Your model must provide transpiration mechanisms. Pumping plant models may become saturated with water and might, due to pressure of pumping, explode. (Be on the lookout for potentially messy situations!)

It doesn't matter if the model in no way simulates what actually occurs in plants. 'Success' should be measured by the design/production of a reasonable model that accounts for the following processes:

• water up-take by roots from the soil

• water transport from the roots through the main stem/trunk

• water transport through branches/petioles to leaves

Once you have completed your model, evaluate and decide if this is a successful model, considering the background information.

Optional: If you don't quite understand capillary action, then try one of these:

1. Water has the ability to travel in narrow spaces by capillary action.
   • Tightly sandwich two glass slides together and briefly touch one corner to the surface of some coloured water.

   • Observe what happens to the water trapped between the slides.

   • Note the appearance of the upper edge of the film of water as it moves between the slides.

2. Capillary action allows water to move higher through narrow openings than through wider openings.
   • Place several tubes of differing widths (e.g., a piece of glass tubing and a melting point tube) in the dish of coloured water.

   • Observe the distance the water travels in each tube.

   • Can you account for the difference in height climbed by the water? How might this apply to trees?

Extensions:

Draw a forested area including wildlife, soil, and plants. Illustrate the water cycle within this system.