13. Transgenic tobacco plants over-expressing isopentenyl transferase (IPT) under the control of promoter region of Senescence Associated Receptor kinase (P SARK) were exposed to drought for 15 days followed by re-watering for 7 days. The following hypotheses were proposed regarding changes in the transgenic plants at the end of 7 days of re-watering
A. The plants would be wilted and fail to survive,
B. The plants would be healthy and survive.
C. The plants would show higher production of cytokinin compared to wild type plants.
D.The plants would show higher production of absicic acid compared to wild type plants.
Which one of the following combinations of the above hypotheses is correct?
(1)A and C (2) A and D
(3) B and C (4) B and D
Correct answer: (3) B and C
Key idea
P SARK is a senescence- and stress‑activated promoter. When it drives IPT, the cytokinin‑biosynthetic enzyme, plants produce extra cytokinin specifically under drought/senescence, which:
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Protects photosynthetic machinery and delays leaf senescence.
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Greatly improves drought tolerance, allowing plants to recover after re‑watering.
So after 15 days drought + 7 days re‑watering, PSARK::IPT tobacco is expected to be healthy and surviving (B) and to have higher cytokinin levels than wild type (C).
Evaluation of each hypothesis
A. Plants would be wilted and fail to survive – False
Wild type often shows severe damage after such drought, but PSARK::IPT plants maintain photosynthetic proteins and recover well upon re‑watering, rather than dying.
B. Plants would be healthy and survive – True
Transgenic plants with stress‑inducible IPT exhibit strong drought tolerance and resume growth after water is restored.
C. Higher production of cytokinin compared to wild type – True
IPT catalyzes the key step of cytokinin biosynthesis; under SARK activation during drought/senescence, these plants accumulate more active CK than wild type.
D. Higher production of abscisic acid compared to wild type – False
Both genotypes may show some ABA rise under drought, but SARK::IPT lines are characterized primarily by enhanced cytokinin, with no consistent strong increase of ABA above wild type reported as the main mechanism.
Thus the correct combination is B and C → option (3).
3 Comments
Manisha choudhary
November 28, 2025ABA may bhi bdh skta h or constructive nhi badhega kyoki wild type gene h
Ipt kaa over expression ho rha h jo cytokinin bnayegi
Plant healthy rahega and high cytokinin concentration rahegi
Ck senescence ko delay kr dega
Manisha choudhary
November 28, 2025Thank you so much sir aap k itna achha pdhane ki vajah s hi aaj question easily kr paa rhi hu relate kr paa rhi hu lg nhi rha ese burden saa ki itna bda syllabus h or aap n itne easy way m conceptually smjha diya
M sach btau too LTA join krne s phle mujhe English pdhna bhi sahi s nhi aata tha or ab question solve kr paa rhi aap hi bolte ho bs continuous pdho exam k result ki Mt socho
Pr sir kbhi dr bhi lgta h ki paper random aaya too
Fir bhi m sure hu ki LTA s judi rhi too sach m meri life bn jaayegi because of you sir
Kbhi bhi tension hoti h confusion hota h ekta ma’am bht achhe s smjhte h kya Krna h kya nhi Krna h
Thank you so much sir and ma’am ♥️
Sakshi Kanwar
November 30, 2025The plants would be healthy and survive.
The plants would show higher production of cytokinin compared to wild type plants.
B and C