Chapter 13: Plant Growth and Development Assertion-Reason Questions | biology Class 11 CBSE

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 1

Logic Check

Assertion (A): Plant growth is described as indeterminate or open. Reason (R): Plants retain the capacity for unlimited growth throughout their life due to the presence of meristems at certain locations in their body.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 2

Logic Check

Assertion (A): Expansion of a leaf is considered an example of growth. Reason (R): Growth is an irreversible permanent increase in size, and expansion of a leaf results in a permanent increase in surface area.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 3

Logic Check

Assertion (A): Swelling of a piece of wood when placed in water is considered growth. Reason (R): Growth must be irreversible and accompanied by metabolic processes at the expense of energy.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 4

Logic Check

Assertion (A): In arithmetic growth, plotting length against time gives a sigmoid (S-shaped) curve. Reason (R): In arithmetic growth, only one daughter cell continues to divide after mitosis while the other differentiates, producing a constant rate of increase.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 5

Logic Check

Assertion (A): The sigmoid (S-shaped) growth curve is characteristic of living organisms growing in a natural environment. Reason (R): In geometric growth, both progeny cells retain the ability to divide, but growth eventually slows due to limited nutrient supply, creating the stationary phase.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 6

Logic Check

Assertion (A): Cells in the elongation phase are located at the root apex and are characterised by active cell division. Reason (R): Cells proximal to the meristematic zone show increased vacuolation, cell enlargement, and new cell wall deposition.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 7

Logic Check

Assertion (A): Water is essential for plant growth. Reason (R): Turgidity of cells helps in extension growth and water provides the medium for enzymatic activities needed for growth.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 8

Logic Check

Assertion (A): During differentiation of tracheary elements, cells develop strong lignocellulosic secondary cell walls. Reason (R): These cells need to carry water to long distances even under extreme tension, requiring strong walls that resist collapse.

Reasoning Options

ByteNotes

Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 9

Logic Check

Assertion (A): Formation of interfascicular cambium from parenchyma cells is an example of redifferentiation. Reason (R): Differentiated parenchyma cells regain the capacity to divide under certain conditions, a phenomenon called dedifferentiation.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 10

Logic Check

Assertion (A): Differentiation in plants is described as 'open'. Reason (R): The final structure of a cell at maturity is determined not only by its origin but also by its location within the organ.

Reasoning Options

ByteNotes

Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 11

Logic Check

Assertion (A): Heterophylly in coriander is an example of plasticity due to the environment. Reason (R): In coriander, juvenile plants and mature plants produce leaves of different shapes in response to their developmental stage.

Reasoning Options

ByteNotes

Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 12

Logic Check

Assertion (A): Auxin was first isolated from human urine. Reason (R): Auxin was isolated by F.W. Went from tips of coleoptiles of oat seedlings.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 13

Logic Check

Assertion (A): Removal of the shoot tip in tea plants leads to growth of lateral buds. Reason (R): The apical bud produces auxin that inhibits the growth of lateral buds; removal of the tip eliminates this inhibition.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 14

Logic Check

Assertion (A): 2,4-D does not affect mature monocotyledonous plants. Reason (R): 2,4-D is a synthetic auxin used as a herbicide that selectively kills dicotyledonous weeds.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 15

Logic Check

Assertion (A): Gibberellins are classified as growth inhibitors. Reason (R): Gibberellins promote internode elongation, bolting, and delay of senescence in plants.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 16

Logic Check

Assertion (A): Spraying gibberellins on sugarcane increases its yield. Reason (R): Gibberellins increase the length of the stem in sugarcane, thereby increasing the volume of sugar-storing tissue.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 17

Logic Check

Assertion (A): Kinetin is a naturally occurring cytokinin found abundantly in plant tissues. Reason (R): Kinetin was isolated from autoclaved herring sperm DNA and does not occur naturally in plants.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 18

Logic Check

Assertion (A): Cytokinins delay leaf senescence. Reason (R): Cytokinins promote nutrient mobilisation, which keeps leaves metabolically active and delays their ageing.

Reasoning Options

ByteNotes

Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 19

Logic Check

Assertion (A): Ethylene is classified exclusively as a plant growth promoter. Reason (R): Ethylene promotes fruit ripening, breaks dormancy, and promotes root growth, but it is largely an inhibitor of growth activities and could fit either the promoter or inhibitor group.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 20

Logic Check

Assertion (A): Ethylene promotes abscission of leaves and flowers. Reason (R): Ethylene is synthesised in large amounts by tissues undergoing senescence and promotes senescence and abscission of plant organs.

Reasoning Options

ByteNotes

Chapter sections

Chapter 13: Plant Growth and Development | Assertion-Reason

Assertion (A): Plant growth is described as indeterminate or open. Reason (R): Plants retain the capacity for unlimited growth throughout their life due to the presence of meristems at certain locations in their body.

Assertion (A): Expansion of a leaf is considered an example of growth. Reason (R): Growth is an irreversible permanent increase in size, and expansion of a leaf results in a permanent increase in surface area.

Assertion (A): Swelling of a piece of wood when placed in water is considered growth. Reason (R): Growth must be irreversible and accompanied by metabolic processes at the expense of energy.

Assertion (A): In arithmetic growth, plotting length against time gives a sigmoid (S-shaped) curve. Reason (R): In arithmetic growth, only one daughter cell continues to divide after mitosis while the other differentiates, producing a constant rate of increase.

Assertion (A): The sigmoid (S-shaped) growth curve is characteristic of living organisms growing in a natural environment. Reason (R): In geometric growth, both progeny cells retain the ability to divide, but growth eventually slows due to limited nutrient supply, creating the stationary phase.

Assertion (A): Cells in the elongation phase are located at the root apex and are characterised by active cell division. Reason (R): Cells proximal to the meristematic zone show increased vacuolation, cell enlargement, and new cell wall deposition.

Assertion (A): Water is essential for plant growth. Reason (R): Turgidity of cells helps in extension growth and water provides the medium for enzymatic activities needed for growth.

Assertion (A): During differentiation of tracheary elements, cells develop strong lignocellulosic secondary cell walls. Reason (R): These cells need to carry water to long distances even under extreme tension, requiring strong walls that resist collapse.

Assertion (A): Formation of interfascicular cambium from parenchyma cells is an example of redifferentiation. Reason (R): Differentiated parenchyma cells regain the capacity to divide under certain conditions, a phenomenon called dedifferentiation.

Assertion (A): Differentiation in plants is described as 'open'. Reason (R): The final structure of a cell at maturity is determined not only by its origin but also by its location within the organ.

Assertion (A): Heterophylly in coriander is an example of plasticity due to the environment. Reason (R): In coriander, juvenile plants and mature plants produce leaves of different shapes in response to their developmental stage.

Assertion (A): Auxin was first isolated from human urine. Reason (R): Auxin was isolated by F.W. Went from tips of coleoptiles of oat seedlings.

Assertion (A): Removal of the shoot tip in tea plants leads to growth of lateral buds. Reason (R): The apical bud produces auxin that inhibits the growth of lateral buds; removal of the tip eliminates this inhibition.

Assertion (A): 2,4-D does not affect mature monocotyledonous plants. Reason (R): 2,4-D is a synthetic auxin used as a herbicide that selectively kills dicotyledonous weeds.

Assertion (A): Gibberellins are classified as growth inhibitors. Reason (R): Gibberellins promote internode elongation, bolting, and delay of senescence in plants.

Assertion (A): Spraying gibberellins on sugarcane increases its yield. Reason (R): Gibberellins increase the length of the stem in sugarcane, thereby increasing the volume of sugar-storing tissue.

Assertion (A): Kinetin is a naturally occurring cytokinin found abundantly in plant tissues. Reason (R): Kinetin was isolated from autoclaved herring sperm DNA and does not occur naturally in plants.

Assertion (A): Cytokinins delay leaf senescence. Reason (R): Cytokinins promote nutrient mobilisation, which keeps leaves metabolically active and delays their ageing.

Assertion (A): Ethylene is classified exclusively as a plant growth promoter. Reason (R): Ethylene promotes fruit ripening, breaks dormancy, and promotes root growth, but it is largely an inhibitor of growth activities and could fit either the promoter or inhibitor group.

Assertion (A): Ethylene promotes abscission of leaves and flowers. Reason (R): Ethylene is synthesised in large amounts by tissues undergoing senescence and promotes senescence and abscission of plant organs.

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