The following post is from: PLC Sydney’s Smart Tree Project Blog
PLC Sydney is participating in a scientific program titled the SMART Tree Project, which involves using a solar powered sap flow meter to measure plant water use, the rising and falling levels of sap flow within a tree on the school grounds. This data lets us analyse it with reference to data obtained on temperature, sunlight, humidity and wind direction; that we collect from the automated weather station at our school. We will use it to investigate the different relationships that sap flow has with each of them. Our school has the sap flow meter installed on a lemon scented gum tree Corymbia citriodara which was planted by our first principal Dr. Marden in approximately 1918.
What is sap?
Sap is the fluid, consisting mainly of water with dissolved sugars and mineral salts, which is found circulating through the vascular system of plants carried by xylem cells.
What is sap flow?
Sap flow is the movement of sap through the plant. It is triggered by heat and light which leads to photosynthesis and transpiration and these two processes cause sap to move inside the plant.
How does the sap flow meter work?
The sap flow meter is an Australian invention which is electrically powered by a solar panel located near the near the tree. The meter takes readings every hour and transmits radio signals to receivers located on the roof of our school library. The data is then further transmitted to the science staff where it can be interpreted and analysed.
Every student in years 7 to 10 is graphing ‘sap flow vs temperature’ and ‘sap flow vs humidity’ for their respective birthdays. This allows us to begin to hypothesise what the relationships between sap flow and these natural phenomenons could be.
For example, take a look at these graphs for the 13th of March in 2013:
From looking at graphs such as these, we hypothesise that as humidity decreases, sap flow increases, and as temperature increases, sap flow also increases. We look forward to obtaining more data and creating more graphs so that we can further analyse our results and test our hypotheses.