Cytokinins and Callus Growth — NEET Biology
✅ Asked in NEET 2024F. Skoog observed that callus proliferated from the internodal segments of tobacco stem when auxin was supplied with one of the following, except: (NEET 2024)
F. Skoog observed that callus proliferated from the internodal segments of tobacco stem when auxin was supplied with one of the following, except: (NEET 2024)
Given below are some statements about plant growth regulators: A. All GAs are acidic in nature. B. Auxins are antagonists to GAs. C. Zeatin was isolated from coconut milk. D. Ethylene induces flowering in Mango. E. Abscisic acid induces parthenocarpy. Choose the correct set of statements from the ones given below: (NEET 2024)
You are given a tissue with its potential for differentiation in an artificial culture. Which of the following pairs of hormones would you add to the medium to secure shoots as well as roots? (NEET 2016 Phase 2)
Answer & NCERT explanation
Correct answer: C — Abscisic acid
ABSCISIC ACID was the exception. According to NCERT, Skoog observed that auxin with extract of vascular tissues, coconut milk, or yeast extract promoted callus proliferation from tobacco internodal segments. These contain cytokinins. Abscisic acid is a growth inhibitor that would prevent callus proliferation, making it the exception among the given options.
Read more NCERT concept on the PYQ
F Skoog and his co-workers observed that from the internodal segments of tobacco stems, the callus (a mass of undifferentiated cells) proliferated only if, in addition to auxins the nutrients medium was supplemented with one of the following: extracts of vascular tissues, yeast extract, coconut milk or DNA. Miller et al. (1955), later identified and crystallised the cytokinesis promoting active substance that they termed kinetin.
NTA tests whether students know that callus growth requires both auxins AND cytokinins together, not just one. The key evidence is that tobacco callus only proliferated when auxins were combined with vascular extracts, yeast extract, coconut milk, or DNA—all sources of cytokinins. Students often mistake auxins alone as sufficient for cell division, missing that cytokinins (identified as kinetin) are equally essential. Remember: auxins promote cell elongation, but cytokinins promote cell division. Both are necessary for complete callus development. Coconut milk is a classic NEET answer—it contains natural cytokinins. This concept appears repeatedly because it tests fundamental understanding of plant hormone interactions.
What does NCERT say about F Skoog and his?
Has this concept appeared in NEET?
Which chapter is this from?
Through deep analysis of NEET and NTA, 88 of 90 questions from the NEET 2026 paper were matched straight from the MedicNEET Biology question bank.
88/90MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.