Growth Phases and Types Practice Questions
20 free Growth Phases and Types practice questions for the NCERT Biology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Plant growth is unique because plants retain the capacity for unlimited growth throughout their life. This ability is due to the presence of:
- A Permanent tissues
- B Meristematic tissues
- C Differentiated cells
- D Parenchyma cells
Correct answer: Meristematic tissues
Plant growth is described as 'open' because of the presence of meristems at certain locations. These cells have the capacity to divide and self-perpetuate, adding new cells to the plant body indefinitely.
The increase in the length of the plant axis along the longitudinal plane is primarily termed as:
- A Secondary growth
- B Lateral growth
- C Primary growth
- D Tertiary growth
Correct answer: Primary growth
Primary growth is the result of apical meristem activity at the tips of roots and shoots. This growth phase is responsible for the elongation of the plant.
Which of the following meristems appear later in the life of dicotyledonous plants and gymnosperms to increase the girth of the organs?
- A Root apical meristem
- B Shoot apical meristem
- C Lateral meristems (cambium)
- D Intercalary meristems
Correct answer: Lateral meristems (cambium)
Lateral meristems, such as the vascular cambium and cork cambium, are responsible for secondary growth. This increases the diameter or girth of the plant parts.
Which phase of growth is characterized by cells having dense protoplasm, large conspicuous nuclei, and thin cellulosic primary cell walls?
- A Phase of elongation
- B Phase of maturation
- C Meristematic phase
- D Senescence phase
Correct answer: Meristematic phase
In the meristematic phase, cells are constantly dividing. They possess rich protoplasm and abundant plasmodesmatal connections to facilitate rapid growth and communication.
Increased vacuolation and new cell wall deposition are hallmark features of which zone of growth?
- A Meristematic zone
- B Zone of elongation
- C Zone of maturation
- D Quiescent center
Correct answer: Zone of elongation
Cells in the zone of elongation undergo significant enlargement. This involves the expansion of the vacuole and the stretching/deposition of the cell wall to increase the cell's volume.
In arithmetic growth, if we plot the length of the organ against time, what kind of curve is obtained?
- A Sigmoid S-curve
- B Straight linear curve
- C Exponential J-curve
- D Parabolic growth curve
Correct answer: Straight linear curve
Arithmetic growth follows the equation Lt = L0 + rt, which is a linear function. This indicates a constant increase in growth per unit time.
Which of the following mathematical expressions correctly represents geometric growth?
- A Lt = L0 + rt
- B W1 = W0 e^rt
- C W0 = W1 e^rt
- D L0 = Lt + rt
Correct answer: W1 = W0 e^rt
Geometric growth is exponential and is expressed as $W_1 = W_0 e^{rt}$. Here, $r$ represents the relative growth rate and also the measure of the ability of the plant to produce new plant material.
A sigmoid curve is a characteristic of which of the following?
- A Cells growing in culture with unlimited nutrients
- B Any organism growing in a natural environment
- C Root elongation in the zone of cell division
- D Only the initial lag phase of growth
Correct answer: Any organism growing in a natural environment
The S-curve or sigmoid curve is typical for all living organisms growing in a natural environment. It consists of a lag phase, a log/exponential phase, and a stationary phase.
In the equation W1 = W0 e^rt, the parameter 'r' is known as:
- A Absolute growth rate
- B Efficiency index
- C Base of natural logarithms
- D Final size
Correct answer: Efficiency index
The relative growth rate 'r' is also called the efficiency index. It is a measure of the plant's capacity to produce new biological matter.
If a leaf grows from 5 cm² to 10 cm² in one day, and another leaf grows from 50 cm² to 55 cm² in the same time, what can be said about their growth?
- A Their absolute and relative growth rates are both different
- B Their relative growth rates are the same as each other
- C Their absolute rates are equal but relative rates differ
- D Both their absolute and relative growth rates are identical
Correct answer: Their absolute rates are equal but relative rates differ
Both leaves added 5 cm² (same absolute growth rate). However, the first leaf doubled its size (100% relative growth), while the second only added 10% (different relative growth rates).
The measurement and comparison of total growth per unit time is called:
- A Relative growth rate
- B Absolute growth rate
- C Exponential growth
- D Arithmetic growth
Correct answer: Absolute growth rate
Absolute growth rate is the total growth measured over a specific time interval. In contrast, relative growth rate is the growth per unit time as a proportion of the initial parameter.
Which of the following is NOT an essential requirement for plant growth?
- A Water for maintaining cellular turgidity
- B Oxygen for aerobic respiration in roots
- C Mineral nutrients for enzyme activity
- D Carbon monoxide for cell wall synthesis
Correct answer: Carbon monoxide for cell wall synthesis
Water, oxygen and mineral nutrients are all genuine requirements: water maintains turgor and acts as a solvent, oxygen supports aerobic respiration in root tissue, and mineral ions serve as enzyme cofactors. Carbon monoxide plays no part in building the cell wall or in any other growth process; it binds metalloenzymes and is toxic to plant metabolism.
Water is essential for plant growth primarily because it:
- A Is the only source of oxygen for the plant
- B Provides turgidity needed for cell extension
- C Provides gravitational stability to organs
- D Is used only in the photosynthesis reaction
Correct answer: Provides turgidity needed for cell extension
Turgidity of cells helps in extension growth. Additionally, water provides the medium for enzymatic activities required for growth processes.
What happens to the daughter cells in arithmetic growth following mitotic division?
- A Both daughter cells continue to divide equally
- B Both daughter cells differentiate and mature fully
- C One daughter cell divides; the other differentiates
- D Both daughter cells undergo senescence and die
Correct answer: One daughter cell divides; the other differentiates
Arithmetic growth is defined by one daughter cell remaining meristematic and continuing to divide, while the other matures and differentiates into a permanent cell.
The log phase in a geometric growth curve is characterized by:
- A Very slow growth
- B Rapid, exponential growth
- C Zero growth rate
- D Growth slowing down due to nutrient depletion
Correct answer: Rapid, exponential growth
Following the initial slow lag phase, the log phase (or exponential phase) sees both daughter cells dividing rapidly, leading to a massive increase in size or number.
Which parameter is typically used to measure the growth of a single maize root apical meristem cell?
- A Surface area
- B Length
- C Cell number
- D Volume
Correct answer: Cell number
In maize, root apical meristems can produce more than 17,500 new cells per hour. Therefore, increase in cell number is the most appropriate parameter for measurement.
Growth of a pollen tube is best measured in terms of its:
- A Weight
- B Surface area
- C Length
- D Volume
Correct answer: Length
For filamentous or tube-like structures such as pollen tubes, growth is expressed as an increase in length as it travels through the style.
Secondary growth is absent in which of the following plant groups?
- A Gymnosperms
- B Dicotyledonous plants
- C Monocots (monocotyledons)
- D Woody perennials
Correct answer: Monocots (monocotyledons)
Monocots generally lack lateral meristems (vascular and cork cambium). Consequently, they do not undergo secondary growth to increase their girth.
Environmental signals like light and gravity affect which stage of growth?
- A Only the meristematic phase of growth
- B Only the maturation phase of growth
- C Specific growth phases and direction
- D They have no effect on plant growth
Correct answer: Specific growth phases and direction
Environmental factors like light and gravity act as signals that influence the direction of growth (tropisms) and various stages of the plant's developmental phases.
The phase of maturation is located:
- A At the very tip of the shoot
- B Proximal to the phase of elongation
- C In between the meristematic and elongation phases
- D Only in the roots
Correct answer: Proximal to the phase of elongation
The maturation phase occurs further away from the apex, behind the phase of elongation. In this zone, cells attain their maximal size and undergo structural differentiation.