Question

a scientist investigated the uptake of mineral salts by the roots of young cereal plants. this is what she found:
a) salts were taken up even when they were more dilute in the soil water than inside the root
b) the rate of uptake was increased raising the temperature by 40 degrees C
c) uptake was stopped if the roots were treated with poison that prevented metabolism
d) uptake was much slower if the soil was waterlogged.

What conclusions can be drawn from each of these findings? how might they help farmers?

Answer 1

The first piece of information, A, tells you that the salt minerals are transported against their concentration gradient. That means there must be a specific transport protein in the membrane which performs the active transport of the mineral salts.

The third peice of info, C, basically confirms this. Metabolism produces ATP and active transport depends on ATP. If metabolism stops, no more ATP is produced and the transporter can't function.

Is that enough to start you off on the problem... ?

Answer 2

how is A helpful to farmers

Answer 3

That's the obvious part: I'd look at that part at the end.

First I'd worry about why salt uptake is highest at 40 degrees C and why waterlogged soil lowers salt increase.

Answer 4

Do you have any ideas about those other two pieces of info...?

Answer 5

for B i think the answer is the plants are able to take in salts at temperatures up to 40*C anything higher salt will not be taken up by the roots

Answer 6

No, that's just a restatement of the info the problem gives you. I think it has more to do with metabolic rate. The metabolic rate is highest at temperatures around 40 degrees C (for grains), so the plant has more ATP available.

Make sense?

Answer 7

what is ATP

Answer 8

ATP is a molecule in which cells store energy. When cells have a lot of ATP, they can use it to do power many processes like (in this case) the uptake of salts through active transport.

Answer 9

i still don't understand answer to A what conclusion is to be drawn and how is it helpful to farmers. lets start off with this question please because the answer is not obvious to me

Answer 10

OK.

Piece of info A tells you that cells still take up salts even when the concentration of salts is higher inside the cells than in the soil. Do you know what concentration gradients and active transport are?

Answer 11

yes

Answer 12

Cool.

Active transport - that is, transport against a concentration gradient - requires energy. Do you understand that?

Answer 13

yes

Answer 14

That energy comes from metabolism inside the cell. Metabolism in a cell is like an engine in the car - it produces a lot of energy, but the engine doesn't sit on the ground and make the car go. Instead, it transfers the energy to the wheels and the wheels make the car move.

Metabolism actually produces a small molecule called ATP. ATP diffuses through the cell and powers various processes, in this case the uptake of salt through active transport.

Does that make sense?

Answer 15

is all this related to A

Answer 16

Yes, it is.

As we have already established, A says that the salt is taken up into the roots against its concentration gradient. That means it's taken up through active transport. The energy which powers active transport has to come from somewhere, doesn't it?

Answer 17

Is that not clear?

Answer 18

how does knowing all of this prove helpful to farmers

Answer 19

You have to understand the info given before you can start drawing conclusions from it. We'll get to implications for farmers then.

Answer 20

does eznymes and reactions have anything to do with B higher than the optimum temperature enzymes will become denatured

Answer 21

No. If temperatures were significantly higher, then denatured proteins would come into it, but not at 40 degrees.

We'll move onto B when you understand that:

1. Salt uptake into roots against a concentration gradient is done through active transport.

2. Active transport requires energy.

3. The energy for active transport comes from metabolism?

Answer 22

Is that clear...?

Answer 23

yes

Answer 24

OK. Now onto B.

Metabolism is highest at 40 degrees C. That means that under these conditions, a great deal of energy is available to cells. Because a great deal of energy is available to cells, they can transport a lot of salt molecules against the concentration gradient.

(The energy is stored and used in a form called ATP which is why I mentioned it in the first place, but that's really a detail.)

Is all that clear?

Answer 25

C is sort of the opposite of B. B looks at what happens to salt uptake when there is a lot of energy available to cells; C looks at what happens to salt uptake when metabolism is blocked and there is not a lot of energy available to cells.

When there is not a lot of energy available to cells, not a lot of salt gets taken up.

It's nice for you to confirm that this makes sense, or to ask now if you don't. ;D

Answer 26

it does

Answer 27

Now onto D.

It says that when the water concentration gradient between the cell and the soil is really strong, not a lot of salt gets taken up into the cell. It just means that the transport proteins can't keep up with it and salt leaves the salt faster than it can be transported into it.

Clear?

Answer 28

yeah

Answer 29

So what implications do you think all this has for farmers growing grains?

Answer 30

farmers growing grain should plant at 40*C , dilute soil , not use metabolism poisons and make sure soil is not waterlogged

Answer 31

Yes, pretty much.

It depends on whether farmers want mineral salts to get into the plants or whether they want them not to get into the plants (too much is toxic). If they do want salts to get into the plants, they should grow them in conditions of high metabolic activity and relatively dry soil. If they don't want salts in the plants, they should grow them in conditions of low metabolic activity and wet soil.

I'm glad you understand it now!

Answer 32

thanks blue could you look at my question at the top of this one

Answer 33

I already looked at it and I don't know the answer. Plant biology is not the field I'm in.

Answer 34

thanks for your help anyway

Answer 35

Sure, not a problem!