UPSC Prelims 2013 · GS Paper I
Question 97: Science and Technology
Mycorrhizal biotechnology has been used in rehabilitating degraded sites because mycorrhiza enables the plants to
- 1.resist drought and increase absorptive area
- 2.tolerate extremes of pH
- 3.resist disease infestation
Select the correct answer using the codes given below.
AnswerUPSC’s answer is (d).
Mycorrhiza is a symbiotic association between fungi and plant roots. The fungal threads extend the root's absorptive area, helping the plant take up water and nutrients and resist drought. They also help plants tolerate extremes of soil pH and protect roots against some pathogens. These benefits make mycorrhiza useful in restoring degraded land, so all three statements are correct.
- 1. Fungal threads extend the absorptive area and help in drought.
- 2. Mycorrhiza helps plants tolerate extremes of pH.
- 3. It helps plants resist some root diseases.
How you could have got this
- If you were sure statement 1 is correct, (b) goes: it leaves 1 out.
What you needed to know: Fungal threads extend the absorptive area and help in drought.
- Then, if you were sure statement 2 is correct, (a) and (c) go: each of them leaves 2 out.
What you needed to know: Mycorrhiza helps plants tolerate extremes of pH.
Only (d) is left. You didn’t need statement 3.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Wrong. It also helps with pH extremes and disease resistance.
- (b) Wrong. Drought resistance and extra absorptive area also apply.
- (c) Wrong. Tolerance of pH extremes also applies.
- (d) Correct. All three benefits apply.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2013, General Studies Paper I, Series A. The paper on upsc.gov.in.