Question 1

Start of synthesis of chlorophyll in a plant seedling is stimulated by

Accepted Answer

Light. Light stimulates chlorophyll synthesis in seedlings by promoting de-etiolation and activating the pathways needed for chloroplast development. In darkness, seedlings remain etiolated and chlorophyll production is suppressed.

Question 2

Typical growth curve in plants is:

Accepted Answer

Sigmoid. The typical growth curve in plants is sigmoid because growth is initially slow, then becomes rapid during the exponential phase, and finally slows as resources and space become limiting. This produces an S-shaped curve.

Question 3

Senescence as an active developmental cellular process in the growth and functioning of a flowering plant, is indicated in:

Accepted Answer

leaf abscission. Leaf abscission is a classic example of senescence acting as an active developmental process: cells in the abscission zone undergo controlled changes that lead to leaf detachment. The other options involve differentiation or lifespan patterns, but not the clearest visible sign of senescence.

Question 4

Coiling of garden pea tendrils around any support is an example of:

Accepted Answer

thigmotropism. Coiling of pea tendrils happens because the plant grows toward the side that contacts the support, producing a directional response to touch. That makes it a tropic movement, specifically thigmotropism.

Question 5

Opening of floral buds into flowers, is a type of:

Accepted Answer

autonomic movement of growth. Opening of floral buds is caused by internal growth changes within the flower tissues, so it is an autonomic movement. Because it depends on growth rather than reversible turgor change, it is specifically an autonomic movement of growth.

Question 6

Movement of leaves of Sensitive Plant, Mimosa pudica are due to:

Accepted Answer

seismonasty. Sensitive plant leaves fold in response to mechanical disturbance such as touch or vibration. That type of nastic movement is called seismonasty.

Question 7

If a tree, flowers thrice in a year (Oct., Jan. and July) in Northern India, it is said to be:

Accepted Answer

photo and thermoinsensitive. Flowering in October, January, and July occurs under very different photoperiods and temperatures. Since the plant flowers repeatedly regardless of these seasonal changes, it is considered insensitive to both light and temperature cues.

Question 8

Thigmotropic movement is best shown by

Accepted Answer

movement in tendril. Thigmotropic movement is a growth movement triggered by touch. Tendrils respond by curling around a support, which is a classic example of thigmotropism.

Question 9

Klinostat is employed in the study of

Accepted Answer

growth movements. A klinostat slowly rotates a plant so gravity acts equally from all sides, preventing a directional response. This lets scientists study growth movements, especially tropic responses, without the influence of constant gravity.

Question 10

Bananas can be prevented from over-ripening by

Accepted Answer

refrigeration. Refrigeration slows enzymatic activity and respiration in bananas, which delays the ripening process and helps prevent over-ripening. Room temperature speeds ripening, freezing damages texture, and ascorbic acid mainly prevents browning rather than ripening.

Question 11

Apical dominance is caused by

Accepted Answer

auxin in shoot tip. Apical dominance is controlled by auxin made in the shoot tip. This auxin moves downward and suppresses the growth of lateral buds, so the main shoot keeps growing preferentially.

Question 12

Phytohormones are:

Accepted Answer

regulators synthesised by plants and influencing physiological processes. Phytohormones are plant hormones: substances synthesized by plants that act in very small amounts to regulate physiological activities. This definition is broader than just flowering, secondary growth, or a single life stage.

Question 13

The hormone responsible for apical dominance is

Accepted Answer

IAA. IAA (indole-3-acetic acid) is the principal auxin produced in the shoot apex. It inhibits lateral bud growth, which creates apical dominance.

Question 14

The ability of the Venus fly trap to capture insects is due to:

Accepted Answer

rapid turgor pressure changes. The Venus flytrap closes when trigger hairs are stimulated, causing rapid changes in turgor pressure in the trap cells. This sudden pressure shift makes the leaf snap shut quickly enough to catch prey.

Question 15

The closure of lid of pitcher in a pitcher plant, is due to

Accepted Answer

turgor movement. The lid movement in a pitcher plant happens because cells change their turgor pressure, causing the structure to open or close. Since the movement is driven by water pressure changes rather than growth or a directional stimulus, it is a turgor movement.

Question 16

Which is produced during water stress that brings stomatal closure:

Accepted Answer

abscisic acid. Abscisic acid (ABA) is the key hormone produced in response to water stress. It accumulates in leaves and causes stomata to close, reducing transpiration and helping the plant conserve water.

Question 17

Grass leaves curl inwards during very dry weather. Select the most appropriate reason from the following:

Accepted Answer

Flaccidity of bulliform cells. Grass leaves curl inward because bulliform cells lose water and become flaccid. This reduces the tension that keeps the leaf blade flat, so the leaf rolls inward to reduce water loss.

Question 18

Read the following four statements (A-D). How many of the above statements are correct?
(A) Both, photophosphorylation and oxidative phosphorylation involve uphill transport of protons across the membrane.
(B) In dicot stems, a new cambium originates from cells of pericycle at the time of

Accepted Answer

Three. Statements A, B, and D are correct, while C is incorrect. Photophosphorylation and oxidative phosphorylation both move protons against their gradient; dicot stems form new cambium from pericycle cells during secondary growth; and many symbiotic nitrogen-fixers also exist freely in soil. Gloriosa and Petunia do not have polyandrous stamens.

Question 19

Etiolation is the response of a plant to stimuli. When plant seeds are grown in insufficient light, (either in partial or complete absence of light) the seedlings will have long, weak stems, smaller and fewer leaves because of longer internodes, and a pale yellow colour (chlorosis). This i

Accepted Answer

Etiolation. Etiolation is the developmental response of plants grown with too little light, producing long weak stems, small leaves, and pale color. Chlorosis is the yellowing symptom, but the overall growth response described is etiolation.

Question 20

The wavelength of light absorbed by Pr form of phytochrome is

Accepted Answer

680 nm. Phytochrome exists mainly as Pr and Pfr. The Pr form absorbs red light, with a peak around 660–680 nm, which converts it to Pfr; among the options, 680 nm matches this absorption best.

NEET Biology: Plant Growth and Development questions with solutions

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