A Level practical on transpiration

Discussion in 'Supporting Biology' started by Jimbob1988, Nov 27, 2019.

  1. Afternoon hive mine,

    Lone trainee tech calling in!

    Have a teacher requesting a transpiration practical which uses a potometer to measure the rate of transpiration. I'm trying to blitz through other activities that my senior/helper would be doing (when someone comes in to replace him eventually maybe. .), and I came across this request before d-day (when I set up the practicals).

    Any tips in advance for this one?

    Many thanks :)
  2. Which exam board are you using?
  3. Insist that the requisition for practicals must be made 1 week in advance. This will minimise any stress to yourself and any potential accidents.:);)
  4. OCR
  5. Have you any potometers?
  6. If it's PAG 5.3 they give instructions for home-made type potometers using small glass jars with graduated pipette and a syringe inserted into a bung. I suppose you could use a commercially bought one but either way they will need setting up for the pupils before the lesson. They then just have to expose the leaves to different conditions such as dark or wind ( hair dryer) and weigh periodically to note changes. Do you have a file with all of the PAG's printed? If not, ask your exams officer for access to the OCR interchange - then you can access all of the student and technician sheets. With assessed A levels that's the best you can do - they aren't really practicals that you can just throw together ( I'm not suggesting that you would) but there's no replacement for the actual instructions from OCR. With potometers they will need setting up in plenty of time because they can be really tricky to get right. The technician sheet has full instructions for setting them up. It6's not the best time of year for leaves either! Hopefully you'll have some good geraniums or similar. :)
  7. Laurel is great and is available all year round being evergreen. There will be a laurel hedge somewhere nearby.
  8. We use the SAPS version and find them very reliable. Assemble everything under water and flush through everything with water (use a syringe) to ensure no air bubbles. Baby food jars needed here but recommend not tasting the baby food - it's disgusting! Why do babies put up with it?
    Jaytee and Peter Sigsworth like this.
  9. looking good:D:D:D:D
  10. Not quite the same as SAPS their video shows them pushing the plant stem through the bung - yours has the stem on a piece of clear nitrile tubing fixed on glass tube through the bung - your adaptation is a much better way in my view.
  11. I like this version @Cricketfool.
    Unfortunately, I'd hear the same thing I always do when I try to adapt pracs...come on everybody..." It's not the same as the picture in the book"!
    Never mind in space, in prep rooms no one can hear you scream!
    ClaireS and Helen J like this.
  12. We have one of these. I am doing it this way:
  13. You are right Jaytee! I usually give them an empty one that looks like the picture in the book and tell them that they rarely work!
  14. Hehe.
    Tried that. :( There should be a 'weeping' emoji on here.
  15. I'm agreeing that this is a better version - I was just pointing out the difference so others who might have missed spotting the change can benefit from it.
    I think if we make adaptations that improve an experiment we should advertise it to the rest.
    Jaytee likes this.
  16. upload_2019-12-4_15-45-11.png
    Jaytee likes this.
  17. I've made a couple of class sets of the SAPS ones and they work a treat. The advantage of having the stem pushed through the bung (I use a core borer to open up the hole while I push the stem through) is that it's really easy to then cut the stem underwater and avoid getting any bubbles blocking the system. Laurel stems are the perfect diameter, usually. Not that I've tried the Cricketfool's adaptation - may give it a go some time.
  18. This is the way to do it, with a bit of parafilm for a better seal. :D
    ClaireS likes this.