Can you beat the Giant Redwood? Investigating xylem
Resource
In this lively starter activity to introduce the topic of xylem, students are posed the question ‘Can you beat a Giant Redwood?’. Giant Redwoods can reach 100m tall and have to be able to move the water from their roots, up the trunk, to the very top of the tree. How do they do this?
Pupils are set the challenge to play the role of xylem in a tree, and see how far they can suck water up a straw. Pupils initially think this is quite an easy task.
Give minimal instructions and let students explore what type of tube they need. They will quickly realise once they start experimenting that the column must be continuous with no gaps. Sellotape must seal each joint. This reinforces the waterproof nature of xylem and the fact there needs to be a continuous column of water. The strength and rigidity of the straw represents the strength of the xylem.
This is a good teamwork activity to get a new group working together. Students experiment how far they can suck the water. Some will realise that vertical height as opposed to total distance is a factor to investigate. Students can use a stairwell, or, if safe, can put their straws out of a window to achieve maximum height. The group that can suck the water the furthest will be the winners. They should, with a bit of practice, be able to suck water up to first floor level but will struggle any further. Students will also need to adapt their tube by looking for air spaces which stop the water moving upwards.
You may wish to show the SAPS animation on transport of water and sugar: https://www.youtube.com/watch?v=LQ03xIkLLQU
For older students, you can follow this activity by showing a fascinating video from Veritasium, available on YouTube, in which well-known YouTube scientists are asked to solve the ‘mystery’ of how giant trees are able to suck water so high: https://www.youtube.com/watch?v=BickMFHAZR0
Acknowledgements
This resource was developed by Alan Blount, of Newstead Wood School, Kent, funded by a SAPS Associate Award.
What has been said about the resource?
"Have used this for Edexcel A level Topic 4 for some years now. It really livens up this rather "dry" topic and the competition is always fierce! I think the challenge of sucking up water through the straws really brings home the extraordinary feat of these enormous trees and the brilliant video from Veritasium is an engaging and stimulating follow-up."