This is a version of the AP Biology respiration lab that I’ve modified to be quicker and easier to accomplish in limited class time. It also is teachers like me who realize at the last minute that they’re planning to do a lab for which a key supply is difficult to come by in a rush. I’ve had problems a couple of times finding good seeds to use in the fall – grocery store beans have at times done a better job of growing fungus for me than of germinating. In the fall in the midwest, the easiest and cheapest seeds to find that are guaranteed to germinate are grass seeds so that’s what I used for this lab.
I had student aides mass out the seeds for me (into plastic petri dishes with dry paper towels cut to fit into the bottom of the petri dishes). Then all I had to do was add enough water to thoroughly moisten the seeds (and towels) in half the petri dishes that evening before leaving school. (Don’t forget to leave half of them dry – these are your dormant/non-germinating seeds.) In the morning I checked the seeds again to make sure they were thoroughly moist but not too wet and continued to periodically check them until we used them in the lab.
With this modification the lab went very smoothly and seeds begun on Monday after school were adequately germinated by mid-morning that Thursday (and perfect for the Friday classes). I realize it’s better to keep the volume of seeds (and beads) constant in all the respirometers but most of my students fail to appreciate that subtlety and often get so wrapped up in technique that they miss the key concept – the changing oxygen volumes. This version seemed to work well with those students.