Question 1

Growth in plants is largely restricted to specialised regions of active cell division called:

Accepted Answer

Meristems. Meristematic tissues (apical, lateral, intercalary) retain the capacity to divide, giving plants indeterminate growth.

Question 2

The three phases of growth in a cell/tissue are, in order:

Accepted Answer

Meristematic → elongation → maturation. Cells first divide (meristematic), then enlarge (elongation), then differentiate (maturation).

Question 3

The phenomenon by which cells derived from meristems become structurally and functionally specialised is:

Accepted Answer

Differentiation. Differentiation leads to loss of division ability and acquisition of specific structure/function (e.g. tracheary elements).

Question 4

When living differentiated cells (e.g. parenchyma) regain the ability to divide (as in interfascicular cambium), it is called:

Accepted Answer

Dedifferentiation. Dedifferentiation: mature cells resume meristematic activity (e.g. cork cambium, interfascicular cambium formation).

Question 5

Arithmetic growth is represented by a ______ curve, whereas geometric growth gives a ______ curve:

Accepted Answer

Linear; sigmoid (S-shaped). Arithmetic growth (constant rate) → linear plot; geometric growth (exponential then plateau under limits) → sigmoid.

Question 6

Growth is an ______ event, so it can be measured by increase in fresh weight, dry weight, length, area, volume or cell number:

Accepted Answer

Irreversible and permanent. Growth is defined as an irreversible, permanent increase in size, measurable by several parameters.

Question 7

A plant can keep growing throughout its life because it retains regions of perpetually dividing cells at root and shoot tips. This ability of plants to grow indefinitely is termed:

Accepted Answer

Indeterminate (open form of) growth. The presence of meristems retaining the capacity to divide throughout life gives plants an open (indeterminate) form of growth, unlike the determinate growth typical of animals.

Question 8

While studying a leaf, a student notes that its cells are fully mature and no longer divide, yet earlier they had divided and then elongated. The cells are currently in which phase of growth?

Accepted Answer

Phase of maturation. After the meristematic (division) and elongation phases, cells attain their final size and functional maturity in the phase of maturation, where differentiation is completed.

Question 9

An instrument used in the laboratory to measure linear increase in the length of a plant shoot over time is the:

Accepted Answer

Auxanometer. An auxanometer measures growth (increase in length) of a shoot; a potometer measures transpiration/water uptake and a porometer measures stomatal opening.

Question 10

A single leaf of a plant may show different leaf shapes on the same plant depending on whether it develops in air or under water, as in Buttercup. This ability of a genotype to produce different forms in response to environment is called:

Accepted Answer

Plasticity. Plasticity is the ability of plants to follow different developmental pathways in different environments; heterophylly in Buttercup, Cotton and Coriander is a classic example.

Question 11

Which sequence correctly represents the change in a plant cell that first loses, and then regains, and again loses its capacity to divide, as seen in the formation of secondary vascular tissue?

Accepted Answer

Differentiation → dedifferentiation → redifferentiation. A differentiated cell first dedifferentiates (regains division capacity, e.g. interfascicular cambium) and then redifferentiates to form mature tissue; hence differentiation → dedifferentiation → redifferentiation.

Question 12

The plot of total plant size against time gives an S-shaped (sigmoid) curve. The three successive phases of this curve are, in the correct order:

Accepted Answer

Lag phase, log (exponential) phase, stationary (senescent) phase. A sigmoid growth curve rises slowly (lag phase), then rapidly (log/exponential phase), and finally levels off as growth slows (stationary phase).

Question 13

In arithmetic growth following a root-tip division, only one daughter cell continues to divide while the other differentiates. The rate of growth in this pattern is best described as:

Accepted Answer

Constant, giving a linear increase in length with time. In arithmetic growth one derivative keeps dividing while the other matures, so length increases at a constant rate producing a straight (linear) plot against time.

Question 14

Match the growth expression with its description: (i) L t = L 0 + rt  (ii) W 1 = W 0 e^{rt}. Choose the correct pairing:

Accepted Answer

(i) arithmetic growth — linear plot; (ii) geometric growth — exponential plot. L t = L 0 + rt describes arithmetic (linear) growth, whereas W 1 = W 0 e^{rt} is the exponential expression of geometric growth, where r is the relative growth rate.

Question 15

Two leaves of the same species, one small and one large, each add 5 cm² of area in a day. Which parameter best captures that the small leaf has grown more impressively relative to its own size?

Accepted Answer

Relative growth rate. Absolute growth rate is identical (5 cm²) for both, but relative growth rate (growth per unit existing size per unit time) is greater for the smaller leaf, revealing its faster proportional growth.

Question 16

Development in a plant is best defined as the sum of two processes acting together throughout the life of the plant. These two processes are:

Accepted Answer

Growth and differentiation. Development is the sequence of changes an organism goes through in its life and is the combined effect of growth and differentiation.

Question 17

Auxanometer is meant for measuring -

Accepted Answer

Growth activity. An auxanometer is an instrument used to measure the growth (linear elongation) of a plant.

Question 18

Which one of the following plants does not show plasticity?

Accepted Answer

Maize. Heterophylly/plasticity is shown by cotton, coriander, larkspur and buttercup; maize (a monocot) does not show this plasticity.

Question 19

Arithmetic growth is related to :-

Accepted Answer

Lt = L0 + rt. In arithmetic growth the length at time t is given by Lt = L0 + rt, where r is the growth rate.

Question 20

In plants, growth is -

Accepted Answer

All the above. Growth is an irreversible permanent increase in size, occurring in certain regions/structures, so all statements apply.

Growth, Phases & Differentiation — NEET Biology MCQs with Solutions

Questions with solutions