Watching gas bubble up from a pondweed as it photosynthesises can be a great demonstration or student practical. When placed closer to a light , the rate of bubbling will speed up, and as the pondweed is taken further away, the bubbles will slow down again - an instant and visual indicator of the importance of light in photosynthesis.
This video demonstrates how best to use this protocol with your students in the lab, which species of pondweed can be used, how to care for pondweeds and a short explanation on the physiology that allows pondweed to bubble.
A great lab practical for investigating photosynthesis and respiration at GCSE and A-level / post-16. The bubbles produced by pondweed can be counted and the rate of bubbling can serve as an indication of the rate of photosynthesis, or the gas can be collected in a pipette or microsyringe and the amount measured. Students can investigate the effects of either light intensity or the wavelength (colour) of light on photosynthesis.
0:00 Introduction
0:59 Different types of pondweed
3:35 Keeping pondweed healthy
5:37 Setting up the bubbling pondweed practical
10:04 Why does pondweed bubble?
12:03 Summary
Full teaching notes are available at www.saps.org.uk/pondweed
#scienceexperiment #photosynthesis #plantscience #saps