The Rate of Starch Synthesis in Destarchred Leaf Discs
7 student responses
Apparently lactose doesn't work, so you can use it as a comparison group
you are planning an experiment to determine the effect of this variables on the rate of starch synthesis, you don't have to actually know the result- but make a justifiable prediction
I'm doing this same planning exercise at the moment, and those two variables seem like the most logical ones to choose. BUT I don't know how to measure the rate of starch synthesis, cos surely if you test the leaf for starch by boiling it in ethanol etc, you've killed said leaf, so if it doesn't have any starch after however many minutes then you have to start again with another disc? So it'll be biased?
And I don't think it matters if some of the sugars don't work, thats the whole point of it
Hey alex. (found you on biomad as well :P).
Well from what ive been thinking and reading about maybe u don't boil the disc's in alcohol until after the leaf has been in the sugar solution.
So the leaf disc's been in the solution for a while, take it out, boil it to remove chorophyll and then test for starch- therefore allowing teh leaf to respire and tehrefore making starch from glucose and then u can boil it and then get the result?
Sound logical? maybe meigh was making it sound harder and mroe complicated then it actually is... ?
Heya! Yeah you don't boil them til after it's been in the sugar, but how do you know how long to leave them in there for before you test them?! But I spose she is good at makin things sound too complicated....
Well it seems I'm not the only one struggling with this ... how do you measure the rate? The best I could come up with was taking a leaf disc out of the solution every hour or whatever, but apart from getting a tape measure and measuring the blue black areas of the leaf, I cant come with a way of showing the change. Unless you simply say theres more blue black after two hours than 1?? My 'teacher' suggested using a colorimeter ... so what wash the the leaf in water and measure the different values, but surely the iodine solution would have a similar colorimeter value to the blue black solution ...? (or I am now making it too complicated?)
im sure you could use a different colour filter so that you only measure the percentage transmission of the one colour of light therfore eliminating the values for the iodine solution. if you use a red filter then only red light can enter the solution. as the blue/black solution will absorb this light the more starch present the stronger the solution and the less red light transmitted! the iodine will allow the red light to be transmitted and so should not affect the results.