Q&A - P3 Science

[atutor2001]

MdmKS:

Got this problem from my P3 child worksheet.


A conical flask contain some water and a plant with its roots submerged in the water. A stopper is fixed at the mouth of the flask holding the stem of the plant with its leaves hanging outside the conical flask. Sorry, I am not sure how to upload the image file here.
Question : how to reduce the rate of water being absorbed by the roots? Give 2 methods, without changing the setting of the experiments.

T!A

My answers are :
1. Cover the leaves with vaseline (but will this change the setting? )
2. Keep in a dark place to stop photosynthesis
3. Keep in a cold place to reduce transpiration

[watmekiasu]

Full.Cream:

watmekiasu:

i - pluck out all the leaves

A typical answer from a GEPer!

I wasn't raised here. Not even sure if I cld hv gotten into Express Stream, not to mention GEP.

[tianzhu]

atutor2001:

My answers are :

1. Cover the leaves with vaseline (but will this change the setting? )
2. Keep in a dark place to stop photosynthesis
3. Keep in a cold place to reduce transpiration

Hi
Just wondering if the place where the experiment is carried out is considered as one of the the settings.

Without changing anything, one way is to control the depth of the roots in the water by adjusting the stem at the stopper.A partially submerged root may absorb less water due to less exposed areas of the roots to the water.Not sure if this is logical.

[atutor2001]

tianzhu:

Hi
Just wondering if the place where the experiment is carried out is considered as one of the the settings.

Without changing anything, one way is to control the depth of the roots in the water by adjusting the stem at the stopper.A partially submerged root may absorb less water due to less exposed areas of the roots to the water.Not sure if this is logical.

Hi
I am actually only guessing.

I also don't know whether does \"setting\" include the environment. I take it as that : \"setting\" to mean \"experiment set-up\" so thinking that as long as we don't change the set-up, it will be ok. But then, in normal English usage, setting does include the environment.

[MdmKS]

watmekiasu:

Tricky one. My answer would be :

i - pluck out all the leaves
ii - keep plant in a dark, damp place

Hay, we share the same thinking, but I was not sure if this correct. My son went to school leaving it blank. B..but , must you pluck out all the leaves? :?

[watmekiasu]

I guess plucking the leaves would be changing the setting. But if leaves were plucked, there would be no/less transpiration and photosynthesis.

[MdmKS]

watmekiasu:

I guess plucking the leaves would be changing the setting. But if leaves were plucked, there would be no/less transpiration and photosynthesis.

What I was thinking may be not to pluck all but pluck some leave cos the objective is to slow down the process. BTW, will plcking all the leave cause the plant to die ?

I quite agree with tianzhu's focus on the roots method.

[Zann]

MdmKS:

watmekiasu:

I guess plucking the leaves would be changing the setting. But if leaves were plucked, there would be no/less transpiration and photosynthesis.

What I was thinking may be not to pluck all but pluck some leave cos the objective is to slow down the process. BTW, will plcking all the leave cause the plant to die ?

I quite agree with tianzhu's focus on the roots method.

I was wondering why a need to have a stopper in this set-up intially till I read tianzhu's suggestion.

[atutor2001]

Zann:

I was wondering why a need to have a stopper in this set-up intially till I read tianzhu's suggestion.

I think the stopper is to prevent water lost due to evaporation.

[tianzhu]

atutor2001:

I think the stopper is to prevent water lost due to evaporation.

Hi

I agree with you that the stopper does help to prevent evaporation of water from the flask, but it’s of little relevance to this experiment. The main objective is to find out ways for the plant to absorb less water without changing the experiment settings.

Besides adjusting the depth of the roots in water, I tend to agree with your suggestion of coating the leaves with vaseline/oil. Alternatively you may cover some of the leaves with black pieces of water. This may not be considered as changing the settings but as modification of variables. The plants and flask still remain the same.

MdmKS, please let us know the answers when your child receives them.

And, you may post images by following these links.
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?t=2699&start=15
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?t=3767&start=30