Plant Growth and Development
16 solved NEET Biology previous year questions on Plant Growth and Development, each with the correct answer and a full explanation.
Q1
In the equation GPP - R = NPP. R represents:
✓ Correct answer: c) Respiration losses
ExplanationGPP = Gross Primary Productivity (total energy fixed by photosynthesis) NPP = Net Primary Productivity (energy left for growth and consumption by other organisms) R = Respiration losses (energy used by producers for their own metabolic activities) Correct answer: C. Respiration losses
Q2
The regulator which retards ageing/senescence of plant parts is
✓ Correct answer: a) cytokinin
ExplanationAnswer: A (cytokinin) Cytokinins are a class of plant hormones that promote cell division and differentiation.One of their most significant physiological effects is the ability to delay the process of aging, or senescence, in plant organs such as leaves, flowers, and fruits.This effect is sometimes referred to as the Richmond-Lang effect.Cytokinins achieve this by mobilizing nutrients to the treated area and maintaining metabolic activity.
Q3
What is necessary for ripening for fruits?
✓ Correct answer: a) 80% of ethylene
ExplanationEthylene is a natural, gaseous plant hormone that serves as the primary regulator and initiator of the fruit ripening process in many fruits (climacteric fruits like bananas, tomatoes, apples, etc.). Ethylene is responsible for a cascade of changes during ripening, including the breakdown of cell walls (softening), degradation of chlorophyll (color change from green), and conversion of starches into sugars (flavor and sweetness development).The concentration required for commercial artificial ripening is typically up to 100 ppm (parts per million), which is considered a safe alternative to harmful methods like calcium carbide.The option "80% of ethylene" refers to the high concentration or significant role of ethylene required relative to other factors/hormones.
Q4
It takes very long time for pineapple plants to produce flowers. Which combination of hormones can be applied to artificially induce flowering in pineapple plants throughout the year to increase yield? [NEET 2019]
✓ Correct answer: a) Auxin and Ethylene
ExplanationCorrect Answer: A Explanation: In pineapple, flowering can be artificially induced by the application of ethylene.Ethylene is known to promote flowering in some plants, including pineapple, and is commercially used to ensure uniform and year-round flowering, thereby increasing yield.Auxins, when applied along with ethylene (or ethylene-releasing compounds like ethephon), enhance the effectiveness of this treatment by supporting growth responses associated with flowering induction.Gibberellins generally delay flowering in many plants.Abscisic acid is a growth inhibitor and does not promote flowering.Cytokinins are mainly involved in cell division and delay of senescence.
Q5
Who coined the term Kinetin? [Re-NEET 2020]
✓ Correct answer: d) Skoog and Miller
ExplanationThe term Kinetin was coined by Skoog and Miller in 1955. They discovered it while studying the effect of DNA breakdown products on plant cell division.Kinetin is a type of cytokinin, a plant hormone that promotes cell division (cytokinesis), especially in plant tissues like callus cultures.
Q6
The ability of plants to follow different pathways in response to environment leading to formation of different kinds of structures is called
✓ Correct answer: d) plasticity.
ExplanationThe ability of plants to follow different pathways in response to environmental cues leading to the formation of diverse structures is known as plasticity.This characteristic allows plants to adapt to varying environmental conditions.
Q7
In tissue culture experiments, leaf mesophyll cells are put in a culture medium to form callus. This phenomenon may be called as: [NEET 2023]
✓ Correct answer: a) Dedifferentiation
ExplanationDedifferentiation is when mature mesophyll cells regain the ability to divide, forming callus in tissue culture.Later, under suitable conditions, these callus cells can again differentiate into various types of tissues or even whole plants — a process called redifferentiation.Incorrect options: B. Development: Refers to overall growth and maturation, not loss of specialization.C. Senescence: Means aging or deterioration of cells.D. Differentiation: Refers to specialization of cells, the opposite of dedifferentiation.
Q8
Formation of interfascicular cambium from fully developed parenchyma cells is an example of [NEET 2024]
✓ Correct answer: d) Dedifferentiation
ExplanationD- Dedifferentiation is when mature cells regain the ability to divide, like parenchyma cells forming interfascicular cambium.A. Maturation: Stage of gaining final structure and function.B. Differentiation: Development of cells into specialized types.C. Redifferentiation: When dedifferentiated cells again become specialized for a specific function.
Q9
Spraying sugarcane crop with which of the following plant growth regulators, increases the length of stem, thus, increasing the yield? [NEET 2024]
✓ Correct answer: c) Gibberellin
ExplanationGibberellins (GAs) are known to promote stem elongation by stimulating cell division and elongation.In sugarcane, spraying with gibberellins increases the length of the stem, thereby enhancing the yield.Gibberellins are particularly effective in increasing the internodal length, which is beneficial for sugarcane crops.
Q10
Auxin is used by gardeners to prepare weed- free lawns. But no damage is caused to grass as auxin - [NEET 2024]
✓ Correct answer: d) does not affect mature monocotyledonous plants
ExplanationAuxin is used as a selective herbicide to control dicotyledonous weeds in lawns.It is effective on dicots but does not affect mature monocotyledonous plants like grass because of differences in auxin sensitivity.This property allows gardeners to maintain weed-free lawns without damaging the grass.
Q11
If the apical bud has been removed then we observe
✓ Correct answer: a) More lateral branches
ExplanationThe end of a shoot contains an apical bud, which is the location where shoot growth occurs.Apical bud produces IAA (an auxin) that inhibits growth of the lateral buds called apical dominance.
Q12
One of the commonly used plant growth hormone in tea plantation is
✓ Correct answer: c) Auxin
ExplanationAuxin exhibits apical dominance.Removal of shoot tips usually results in the growth of lateral buds.It is widely applied in tea plantations.
Q13
Which hormone promotes internode/petiole elongation in deep water rice plants?
✓ Correct answer: b) Ethylene
ExplanationIn deep-water rice plants, ethylene plays a key role in helping the plant adapt to flooding.It triggers rapid elongation of internodes and petioles, allowing the upper parts of the shoot and leaves to stay above the water surface for gas exchange and photosynthesis.GA₃ also promotes elongation in many plants, but in the specific case of deep-water rice, ethylene is the key regulator
Q14
Spraying of which of the following phytohormone on juvenile conifers helps in hastening the maturity period, that leads to early seed production? [NEET 2023]
✓ Correct answer: a) Gibberellic Acid
ExplanationWhen gibberellic acid (GA₃) is sprayed on juvenile conifers, it shortens their juvenile phase and helps them reach reproductive maturity faster.This results in early cone and seed formation.Gibberellins are known to promote stem elongation, flowering, and seed development, making them useful in inducing early maturity.Incorrect options: Zeatin: Promotes cell division, not early seed production.Abscisic acid: Induces dormancy and inhibits growth.Indole-3-butyric acid: Promotes root initiation, not flowering.
Q15
F. Skoog observed that callus proliferated from the internodal segments of tobacco stem when auxin was supplied with one of the following except:
✓ Correct answer: c) Abscisic acid
ExplanationF. Skoog (along with C. Miller) discovered cytokinins while studying callus growth in tobacco stem segments.They observed that auxin alone could not induce continuous cell division — it required a cytokinin source, such as: Coconut milk (rich in kinetin-like substances), Yeast extract, or Vascular tissue extract.Abscisic acid (ABA), however, is a growth inhibitor that suppresses cell division and callus proliferation.Therefore, Abscisic acid is the exception.
Q16
Formation of interfascicular cambium from fully developed parenchyma cells is an example for [NEET 2024]
✓ Correct answer: d) Dedifferentiation
ExplanationD- Dedifferentiation is when mature cells regain the ability to divide, like parenchyma cells forming interfascicular cambium.A. Maturation: Stage of gaining final structure and function.B. Differentiation: Development of cells into specialized types.C. Redifferentiation: When dedifferentiated cells again become specialized for a specific function.
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