This SAPS teaching resource provides a fun way for students to get hands-on when investigating photosynthesis, using an easily quantifiable and reliable procedure.
Students punch out small discs from leaves, and float them in a syringe of sodium hydrogen carbonate solution. Once gas is evolved by photosynthesis, the leaf discs rise and fall.
Students can compare the rate of photosynthesis in sun and shade plants and at different light intensities, amongst many other factors. Once introduced to the basic protocol, students can easily develop their own investigations.
Suitable leaves include brassica cotyledons and fresh spinach. To compare photosynthesis in sun and shade-adapted plants, we suggest comparing pelargonium and aspidistra leaves. The
surface should be smooth (avoid plants with hairy leaves), and not too thick.
This resource includes teaching and technical notes, an illustrated students' guide, and a student question sheet.
You may also want to show your students our animation on respiration and photosynthesis.