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this one is dicy

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this one is dicy

by PAB2706 » Sat Jul 25, 2009 7:27 am
A certain cultivated herb is one of a group of closely related plants that thrive in soil with high concentrations of metals that are toxic to most other plants. Agronomists studying the herb have discovered that it produces large amounts of histidine, an amino acid that,in test-tube solutions, renders these metals chemically inert. Possibly, therefore, the herb’s high histidine production is what allows it to grow in metal-rich soils, a hypothesis that would gain support if ______.


A. histidine is found in all parts of the plant—roots, stem, leaves, and flowers
B. the herb’s high level of histidine production is found to be associated with an
unusually low level of production of other amino acids
C. others of the closely related group of plants are also found to produce histidine in
large quantities
D. cultivation of the herb in soil with high concentrations of the metals will, over an
extended period, make the soil suitable for plants to which the metals are toxic
E. the concentration of histidine in the growing herb declines as the plant approaches
maturity
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by ManSab » Sat Jul 25, 2009 8:06 am
I will go for C..
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by nervesofsteel » Sat Jul 25, 2009 11:18 am
IMO E

the concentration might be decreasing with amino acids getting used....

which is the strengthening the conclusion....
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by pandeyvineet24 » Sat Jul 25, 2009 12:05 pm
Should be C.

Rest all of them are not relevant.
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by tom4lax » Sat Jul 25, 2009 4:10 pm
IMO, D.
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by ashton_s_83 » Sat Jul 25, 2009 4:34 pm
I have seen this ques before, the answer is (C)
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by bignasty666 » Sun Jul 26, 2009 11:26 am
closest one seems to be D... how is the OA C? WHAT DO YOU MEAN BY "CLOSELY RELATED PLANTS". Do u mean geographically, compostion wise, functionally...."closely related" is a loose term...if it said "plants cultivated in the same soil" then c would have been more viable option

D because if this herb truly does render the metals inert, then over an extended period metals in that paticular land would be inert....
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E

by sumank8216 » Sun Jul 26, 2009 4:19 pm
E.

I dont know how to explain this one.
Since this tells us that the plant is growing till maturity, so there has to be something, which is supporting it to grow and that is this amino acid. And that amino acid is no more there when the plant is mature(no growth).

So, lets assume this amino acid scretion stops before the plant reaches maturity, the plant wont be able to reach maturity.This tells us this amino acid is needed for its growth.
I dont know if this makes sense ..
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by crackgmat007 » Sun Jul 26, 2009 5:30 pm
Conclusion - the herb’s high histidine production is what ALLOWS it to GROW in metal-rich soils, a hypothesis that would gain support

Need a premise to support conclusion.

IMO E stands out. Histidine production is no longer needed when the herb reaces maturity (growth stops). Hence Histidine production is required for growth.
Last edited by crackgmat007 on Sat Aug 01, 2009 5:50 pm, edited 1 time in total.
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by Spring2009 » Wed Jul 29, 2009 11:14 pm
crackgmat007 wrote:Conclusion - the herb’s high histidine production is what ALLOWS it to GROW in metal-rich soils, a hypothesis that would gain support

Need a premise to support conclusion.

IMO E stands out. Histidine production is no longer needed when the herb reaces maturity (growth stops). Hence Histidine production is required for growth.
What you say is true (No growth -> no histidine)
However, the conclusion (histidine -> growth) will be true if (no histidine -> no growth), this is different from E (no growth -> no histidine).
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by crackgmat007 » Thu Jul 30, 2009 9:49 am
However, the conclusion (histidine -> growth) will be true if (no histidine -> no growth)
If H -> G, IMO we cannot say NO H -> NO G. This will be a mistaken negation, there may be other ways a plant can grow.

But, we can say that if NO G -> then NO H or any other growth stimulents.

That is if plant no longer grows, there is no need for H. I hope my analysis is correct.
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by amazonviper » Thu Jul 30, 2009 10:06 am
IMO C

This is a good question. Here the Histidine makes the metals inert and hence the plant can grow. The Histidine is not being used by the plant to grow. If E were to be true then the decrease in the Histidine can can cause the metals to be active again (which we are not sure because the passage does not state if the inertness is permanent or temporary) and hence kill the plant. We are looking for a reason which will prove the hypothesis correct.

Only C addresses this concern. If we have one common factor in all the plants in the group that live in these conditions, then that will be the prime reason for the plant's sustenance.

I hope I cleared your concern.
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by PAB2706 » Fri Jul 31, 2009 1:15 am
Well the answer given is E... but i think it shud be D

amino acids in histadine makes metals inert....

normal plants cannot grow in soils with high metal concentration

so if this herb grows in a high metal concentration soil, eventually this herb will make the metal in the soil inert.

so if normal plants start growing in this soil then the hypothesis is proved....


In E, i think the plant approaching maturity goes out of scope of the argument.
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by gmat_2010 » Sat Aug 01, 2009 5:44 pm
I don't understand why the concentration decrease over a period of time. The premise states that the plant produces histadine. Hence, I don't get it. Unless...... one implies that the plants eventual death is not because of age but because of increase in toxic metal content.
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by gmat_dest » Sat Aug 01, 2009 7:52 pm
Eliminating A and B since everybody seems to agree that they are not the correct choices.

What is the hypothesis?

Plant X of a closely-related group Y grows in metal rich soils because it secretes Z that renders those metals inert in test-tubes.

C. others of the closely related group of plants are also found to produce histidine in large quantities .

The hypothesis will be strengthened if it can be proven that other members of group Y also exhibit the same behavior.

D. cultivation of the herb in soil with high concentrations of the metals will, over an extended period, make the soil suitable for plants to which the metals are toxic --- If this is true, then any plant can be grown in that soil/ This weakens the hypothsis.

E. the concentration of histidine in the growing herb declines as the plant approaches maturity --- balantantly out of scope. We are not talking about decreasing concentration with maturity anywhere.
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