Grade 11 : Biology - Plants Growth (Set 3)

Question 1

A plant stem apex undergoes distinct phases of growth behind the shoot apical meristem: meristematic, elongation, and maturation phases.

Which of the following structural characteristics is specifically associated with cells located in the phase of elongation?

Accepted Answer

B) Increased vacuolation, cell enlargement, and new cell wall deposition

Answer

A) Dense protoplasm and abundant plasmodesmatal connections

Answer

C) Thick secondary wall deposition and maximum structural differentiation

Answer

D) High rate of cell division with prominent central nuclei

Question 2

An isolated root segment displays arithmetic growth where only one daughter cell continues to divide while the other differentiates.

If the initial length $L_0$ is 10 cm and the growth rate $r$ is 1.5 cm/day, what will be the length $L_t$ of the root after 6 days according to the linear growth formula $L_t = L_0 + rt$?

Accepted Answer

C) 19 cm

Answer

A) 13 cm

Answer

B) 16 cm

Answer

D) 22 cm

Question 3

Two leaves, Leaf A and Leaf B, grow in a greenhouse over a 1-day period. Leaf A increases its surface area from $10cm^2$ to $15cm^2$. Leaf B increases its surface area from $100cm^2$ to $105cm^2$.

Which statement correctly compares their Absolute Growth Rate (AGR) and Relative Growth Rate (RGR)?

Accepted Answer

B) Both leaves have equal AGR, but Leaf A has a higher RGR than Leaf B.

Answer

A) Leaf A has a higher AGR than Leaf B, but their RGRs are equal.

Answer

C) Leaf B has both higher AGR and higher RGR than Leaf A.

Answer

D) Both leaves have equal RGR, but Leaf B has a higher AGR than Leaf A.

Question 4

A researcher placed decapitated oat (Avena sativa) coleoptiles on agar blocks containing a plant hormone, leading to asymmetric curvature when placed on one side of a new coleoptile stump.

Which plant growth regulator is standardly assayed using this Avena curvature test?

Accepted Answer

C) Auxin (Indole-3-acetic acid)

Answer

A) Gibberellic Acid ($GA_3$)

Answer

B) Kinetin

Answer

D) Abscisic Acid (ABA)

Question 5

Rosette plants like cabbage maintain short internodes during vegetative growth but elongate dramatically prior to flowering when treated with a specific phytohormone.

This phenomenon of internodal elongation prior to flowering is known as bolting, and is induced by:

Accepted Answer

B) Gibberellins

Answer

A) Auxins

Answer

C) Cytokinins

Answer

D) Ethylene

Question 6

Detached green leaves treated with a particular phytohormone retain their chlorophyll content and remain green much longer than untreated control leaves.

This delay of leaf senescence by nutrient mobilization is known as the Richmond-Lang effect, and is caused by:

Accepted Answer

B) Cytokinins

Answer

A) Abscisic Acid

Answer

C) Ethylene

Answer

D) Auxins

Question 7

During the ripening phase of climacteric fruits like apples and bananas, there is a sharp and sudden increase in cellular respiration rate.

Which gaseous plant hormone triggers this respiratory climacteric and accelerates ripening?

Accepted Answer

C) Ethylene

Answer

A) Indole-3-butyric acid

Answer

B) Zeatin

Answer

D) Abscisic Acid

Question 8

Under drought conditions, roots detect soil moisture deficiency and signal the leaves to prevent excessive transpirational water loss.

Which plant hormone acts as a stress signal to stimulate rapid closure of stomata?

Accepted Answer

B) Abscisic Acid (ABA)

Answer

A) Gibberellin

Answer

C) Cytokinin

Answer

D) Auxin

Question 9

Differentiated parenchyma cells in the medullary rays of a dicot stem lose their specialized structure and regain the capacity for division to form interfascicular cambium.

This developmental conversion of living mature cells back into meristematic cells is termed:

Accepted Answer

B) Dedifferentiation

Answer

A) Differentiation

Answer

C) Redifferentiation

Answer

D) Plasticity

Question 10

Plasticity refers to the ability of plants to follow different developmental pathways in response to environmental cues or lifecycle phases.

While cotton and coriander show developmental heterophylly, environmental heterophylly (producing distinct leaf shapes in air vs. water) is characteristically shown by:

Accepted Answer

B) Buttercup (Ranunculus)

Answer

A) Larkspur

Answer

C) Maize

Answer

D) Sunflower

Question 11

When plant cells or microorganisms grow in a limited resource environment, growth follows a classic S-shaped (sigmoid) curve governed by $W_1 = W_0 e^{rt}$.

During which phase of this sigmoid curve does growth slow down as nutrients become limiting?

Accepted Answer

D) Stationary phase

Answer

A) Lag phase

Answer

B) Log phase

Answer

C) Exponential phase

Question 12

A farmer wants to selectively eliminate broad-leaved dicotyledonous weeds growing in a field of monocotyledonous cereal crops (wheat).

Which synthetic auxin derivative is commonly sprayed for selective weed elimination?

Accepted Answer

C) 2,4-Dichlorophenoxyacetic acid (2,4-D)

Answer

A) Indole-3-acetic acid (IAA)

Answer

B) Naphthalene acetic acid (NAA)

Answer

D) Indole butyric acid (IBA)

Question 13

A short-day plant (SDP) requires a dark period longer than a critical length to induce flowering.

What happens if the continuous dark period of an SDP is interrupted by a brief flash of red light (660 nm)?

Accepted Answer

B) Flowering is completely inhibited.

Answer

A) Flowering is accelerated.

Answer

C) Vegetative growth stops instantly.

Answer

D) Ethylene synthesis is induced.

Question 14

Apical dominance is a phenomenon where the growing apical bud suppresses the outgrowth of lateral axillary buds.

Which hormone maintains apical dominance, and which hormone counteracts it when applied externally?

Accepted Answer

C) Auxin maintains it; Cytokinin counteracts it

Answer

A) ABA maintains it; Ethylene counteracts it

Answer

B) Gibberellin maintains it; Auxin counteracts it

Answer

D) Cytokinin maintains it; ABA counteracts it

Question 15

Ethephon is an aqueous solution widely utilized in agricultural operations because it is readily absorbed and releases ethylene slowly.

Which of the following is an established agricultural application of Ethephon?

Accepted Answer

B) Promotes female flowers in cucumbers and accelerates fruit ripening

Answer

A) Prevents fruit drop in apples

Answer

C) Induces dwarfism in sugarcane stems

Answer

D) Reverses bolting in cabbage

Question 16

Experiments involving photoperiodic induction demonstrate that removing all leaves from a plant prevents it from responding to light/dark cycles.

What does this experiment reveal about the photoperiodic floral signal?

Accepted Answer

C) Leaves are the primary site of light perception and produce a hormonal signal (florigen).

Answer

A) Shoot apex directly senses light without chemical signals.

Answer

B) Roots synthesize the floral inhibitor in darkness.

Answer

D) Stems store phytochrome while leaves store chlorophyll.

Question 17

Certain winter varieties of wheat sown in spring fail to produce flowers and grain within the growing season unless subjected to a specific environmental treatment.

This requirement of a low-temperature treatment ($1^\circ ext{C}$ to $10^\circ ext{C}$) to promote flowering is called:

Accepted Answer

B) Vernalization

Answer

A) Scarification

Answer

C) Photoperiodism

Answer

D) Stratification

Question 18

Two main phytohormones regulate seed dormancy and germination in an antagonistic manner during seed development.

Which hormone enforces seed dormancy, and which hormone breaks dormancy to promote germination by synthesizing $\alpha$-amylase?

Accepted Answer

C) ABA enforces dormancy; Gibberellin breaks dormancy.

Answer

A) Auxin enforces dormancy; Cytokinin breaks dormancy.

Answer

B) Ethylene enforces dormancy; ABA breaks dormancy.

Answer

D) Gibberellin enforces dormancy; ABA breaks dormancy.

Question 19

Cells produced by the vascular cambium and cork cambium undergo differentiation to form secondary xylem, secondary phloem, and phelloderm.

Because these meristematic cells were themselves formed by dedifferentiation, their secondary maturation into functional non-dividing tissue is called:

Accepted Answer

C) Redifferentiation

Answer

A) Primary differentiation

Answer

B) Secondary dedifferentiation

Answer

D) Senescence

Question 20

In the exponential growth equation $W_1 = W_0 e^{rt}$, parameters represent quantitative metrics of plant organ expansion.

In this equation, what does the variable $r$ signify?

Accepted Answer

C) Relative growth rate and efficiency index

Answer

A) Base of natural logarithms

Answer

B) Final weight after time $t$

Answer

D) Absolute growth duration

Grade 11 : Biology - Plants Growth (Set 3)