Photosynthetic floatation/pond weed required practical - any tips

Afternoon all,

I have the following request from a teacher: https://www.exploratorium.edu/snacks/photosynthetic-floatation.

Also, I have learnt that the pond weed practical is notoriously difficult - any tips/alternatives for this?

Many thanks :)
nice looking practical - i just emails that link to my bio teacher!

for pond weed I would recommend ordering from blades Bio their Egeria Densa - unless you can find it locally - I had this last term, it even grew and got roots and is still alive, but most importantly all the students got results from it in the counting bubbles experiment - its not as good as cabomba but we cant get that anymore so trying other things.
 
Pond weed is such a pain! I keep and grow some egeria (or elodea if you like!) but you can buy it from many garden centres that have an aquarium section (although it is becoming less popular). Practically, as you say, it isn't that reliable... my advice would be to use aged water, at a spatula of sodium hydrogen carbonate and keep your fingers crossed! If it doesn't bubble, cut again (with a scalpel and at an angle) until it does. Good luck!
 
Pond weed is such a pain! I keep and grow some egeria (or elodea if you like!) but you can buy it from many garden centres that have an aquarium section (although it is becoming less popular). Practically, as you say, it isn't that reliable... my advice would be to use aged water, at a spatula of sodium hydrogen carbonate and keep your fingers crossed! If it doesn't bubble, cut again (with a scalpel and at an angle) until it does. Good luck!
Have you seen the new SAPS video - follow this thread
http://community.preproom.org/index...weed-video-and-why-does-pondweed-bubble.5733/
 
Afternoon all,

I have the following request from a teacher: https://www.exploratorium.edu/snacks/photosynthetic-floatation.

Also, I have learnt that the pond weed practical is notoriously difficult - any tips/alternatives for this?

Many thanks :)
Haven't done the one you have but....
We are on our final day of the pond weed practical and it has gone really well. I bought Elodea densa from Lincs pond plants about 10 days prior to the first practical, put all the weed in several containers, snipped their stalk ends and then put them under LED lamps on a timer so they were lit from 6.30 am until 6 pm. I changed the water every 2/3 days. When needed for the practical I 2/3 filled 250ml beakers with tap water and placed a length of weed in each one, snipped the stalk ends and put them back under the lamps a couple of hours before the lesson.
Some teachers told the students to add a half spatula of sodium bicarbonate to their boiling tube of tap water to do the experiment and some didn't. All have worked with excellent bubbling! I am soooo happy :D:D:D
 
Top