Australia's Science Forum

Hi guys,
We are trying to do the experiment with varigated geranium leaves, boiled in meths, then soaked in iodine soln, to indicate the presence of starch on the green parts of the leaves and not present on the white parts of the leaves. But it is not working!!! Anyone else do this experiment and if so what are your secrets for success?

Kathryn

We have done it with varigated leaves, but we had more success with dark green ones. We cover half of the leaf with alfoil in the garden, must be on sun, so when you finish decorating, looks like a xmas tree.
Students (or you) pick the leaves off next day and boil it in metho (use water baths, so as not to burn down the building). Rinse in water ,place on watch glass and cover with iodine solution. Make sure it is quite dark in colour. You will see the colour change on the leaves very soon. Kids get creative and make patterns on the leaves with some parts covered in different shapes.

Good luck
Lada

Hi there,
We have good success with this experiment, but our method may be a little different. We boil the leaves first in water, then place in a test tube with metho which is in a beaker of water on a hotplate. Remove the leaf, flood with iodine solution. Young, soft leaves work best. Try a paddle pop stick across the leaf. Leave a day or two before using method above.
Good luck, Ellice

We use freshly prepared Lugol's Iodine solution, doesn't work if the solution is light or oxidised.

Cheers,
Ana

We had good results with mint leaves

Me again...

I've just tried doing this again ... made up fresh Lugol's soln, boiled leaves in water, boiled in meths, doused in lugols. The whole leaves just turn really dark brown. It doesn't look very exciting at all. How long do you do each step for? Is there a dramatic difference between the light parts of the leaves and the dark parts?
Thanks for your help...
Kathryn

I wonder if you're leaving them too long in the metho. We leave only until metho turns green. Have the leaves been in the sun prior to picking? Freshly picked seems to work well.

We have just done this and it has worked well. The only things I can suggest are leaves need a few hours of sunlight first so don't do it first thing in the morning and rinse the leaf in water before putting it in the iodine solution.

Hi I need suggestions on an alternate plant than geranium or mint to do this experiment.
One that is varigated would be ideal...
My geranium plants are not varigated and the teachers want varigated, and I can't seem to purchase a plant to suit.
PLEASE HELP!!!
Trish.

We use hibiscus. Are you too far south for that? What about Spider plants - not the Spider Lilies, but the little house plant.

Variegated Coleus - leaves are green with a white center.

We have use variegated Hydrangea in the past. May be a problem as they are deciduous.

We did it today using verigated ivy. It worked like a dream. We boiled it for a while, because leaf has a coating on it and needs to be boiled before immersing in metho. Wash well and flood with iodine.

Thanks for the suggestions, I'm going plant shopping this arvo and going to try and source some of your suggestions
Thankyou, Trish.

We used the Chinese lantern plant - wonderful!