Growth Questions in English

(N/A) Plant growth is unique because plants retain the capacity for unlimited growth throughout their life.
This ability of the plants is due to the presence of meristems at certain locations in their body.
The cells of such meristems have the capacity to divide and self-perpetuate.
The product,however,soon loses the capacity to divide and such cells make up the plant body.
This form of growth,wherein new cells are always being added to the plant body by the activity of the meristem,is called the open form of growth.
The root apical meristem and the shoot apical meristem are responsible for the primary growth of the plants and principally contribute to the elongation of the plants along their axis.
In dicotyledonous plants and gymnosperms,the lateral meristems,vascular cambium,and cork cambium appear later in life.
These are the meristems that cause the increase in the girth of the organs in which they are active. This is known as secondary growth of the plant.

(N/A) The diagram shows a comparison of absolute and relative growth rates. Both leaves $A$ and $B$ have increased their area by $5 \ cm^{2}$ in a given time to produce leaves $A^{1}$ and $B^{1}$.
- The quantitative comparison between the growth of living systems is done in the following two ways:
$(1)$ Absolute Growth Rate: It is the measurement and comparison of total growth per unit time.
$(2)$ Relative Growth Rate: It is the growth of the given system per unit time expressed on a common basis,e.g.,per unit initial parameter.
- Leaves $A$ and $B$ shown in the figure have grown $5 \ cm^{2}$ in one day.
Although their initial sizes are different,i.e.,$5 \ cm^{2}$ and $50 \ cm^{2}$ respectively,both show an absolute increase in area in the given time to produce leaves $A^{1}$ and $B^{1}$,which is $5 \ cm^{2}$ in both cases.
Out of these two,the relative growth rate is higher in leaf $A^{1}$ because the initial area of leaf $A$ is smaller compared to leaf $B$.

(D) The cells proximal (just next,away from the tip) to the meristematic zone represent the phase of elongation.
Increased vacuolation,cell enlargement,and new cell wall deposition are the characteristics of the cells in this phase.
Further away from the apex,i.e.,more proximal to the phase of elongation lies the portion of the axis which is undergoing the phase of maturation.
The cells of this zone attain their maximal size in terms of wall thickening and protoplasmic modifications.

(B) The log phase,also known as the exponential phase,is the middle phase of growth.
It is characterized by very fast and rapid growth of the plant body.
After the initiation of growth,the cell number increases rapidly at an exponential rate $(W_1 = W_0 e^{rt})$.
During this phase,both progeny cells resulting from mitotic cell division retain the ability to divide and continue dividing as long as the nutrient supply is adequate.

(N/A) Arithmetic growth is a type of growth where one daughter cell continues to divide while the other differentiates and matures. The simplest expression of arithmetic growth is exemplified by a root elongating at a constant rate.
- Refer to the provided graph, which shows constant linear growth by plotting the length of the organ $(L)$ against time $(t)$.
- On plotting the length of the organ against time, a linear curve is obtained.
- Mathematically, it is expressed as:
$L_{t} = L_{0} + rt$
Where:
$L_{t} = \text{length at time } t$
$L_{0} = \text{length at time zero}$
$r = \text{growth rate / elongation per unit time}$

(N/A) Circummutation is the spontaneous,rhythmic,and circular or elliptical growth movement of the tip of a growing plant organ,such as a stem,tendril,or coleoptile.
This movement occurs because the cells on different sides of the organ grow at different rates in a sequential manner.
As a result,the tip of the growing stem traces a helical or spiral curve in space as it elongates.

(N/A) The stems of plants growing in the dark become long,thin,yellow,and weak due to the lack of light. This specific physiological condition is known as the 'etiolated position' or 'etiolation'.

(N/A) Growth is measured by the increase in size over time.
$1$. Absolute Growth Rate: This is the total growth per unit time.
Absolute Growth Rate = $\frac{\text{Final size} - \text{Initial size}}{\text{Time}} = \frac{19 \, cm - 5 \, cm}{7 \, days} = \frac{14 \, cm}{7 \, days} = 2 \, cm/day$.
$2$. Relative Growth Rate: This is the growth per unit initial size per unit time.
Relative Growth Rate = $\frac{\text{Growth}}{\text{Initial size}} = \frac{19 \, cm - 5 \, cm}{5 \, cm} = \frac{14}{5} = 2.8$.
Thus, the absolute growth rate is $2 \, cm/day$ and the relative growth rate is $2.8$.

(N/A) The sigmoid growth curve represents the growth of an organism or organ over time. The segments are labeled as follows:
$(1)$ Lag phase: This is the initial phase where growth is slow as the organism or cells are adjusting to the environment.
$(2)$ Exponential phase (or Log phase): This is the phase of rapid growth where the rate of growth increases significantly.
$(3)$ Stationary phase: This is the final phase where the growth rate slows down and eventually levels off due to limited resources or other environmental factors.

(A) In living organisms,growth is a characteristic feature.
In plants,cell division occurs continuously throughout their lifespan,which means they exhibit indeterminate growth.
In contrast,animals exhibit determinate growth,where growth occurs only up to a certain age.
Therefore,the correct sequence is Plants and Animals.

(B) The process of plant growth begins with the germination of the seed.
Seed germination is the initial stage where the embryo inside the seed resumes metabolic activity and begins to grow into a new plant under favorable conditions.
Flowering and leaf formation are subsequent developmental stages that occur after the plant has established itself.

(B) In the context of plant growth,specifically regarding the root apical meristem of maize $(Zea \ mays)$,it has been observed that a single cell can divide and produce more than $17,500$ new cells per hour. This high rate of cell division is characteristic of meristematic tissues,which are responsible for the continuous growth of the plant.

(B) According to the $NCERT$ textbook,growth is a fundamental characteristic of living organisms. In certain cases,such as the growth of cells in a watermelon,the cells can increase in size by up to $3,50,000$ times.
This massive increase in cell volume is a classic example of cell enlargement contributing to plant growth.

(C) In the given figure,the first part shows an increase in the length of the plant organ (like a stem or root),which is characteristic of primary growth. This occurs due to the activity of apical meristems.
The second part shows an increase in the thickness or girth of the plant organ,which is characteristic of secondary growth. This occurs due to the activity of lateral meristems (vascular cambium and cork cambium).

(A) The growth of a plant is divided into three distinct phases:
$1$. Meristematic phase: Cells in the root and shoot apices are constantly dividing.
$2$. Elongation phase: Cells proximal to the meristematic zone undergo enlargement,leading to increased cell size.
$3$. Maturation phase: Cells reach their maximum size in terms of wall thickening and protoplasmic modification,becoming specialized for specific functions.
Therefore,the correct sequence is Meristematic $\rightarrow$ Elongation $\rightarrow$ Maturation.

(B) The parameters of growth are measured by different criteria based on the biological structure:
$1$. Maize root apical cells increase in $Number$ $(P-II)$.
$2$. Watermelon cells increase in $Size$ $(Q-III)$.
$3$. Pollen tubes increase in $Length$ $(R-I)$.
$4$. Dorsiventral leaf surfaces increase in $Surface area$ $(S-IV)$.
Thus, the correct matching is $(P-II), (Q-III), (R-I), (S-IV)$.

(D) The region of elongation is characterized by increased vacuolation,cell enlargement,and new cell wall deposition. These processes are essential for the growth of the plant organ. Therefore,all the given options are correct.

(C) In the provided figure,$Q$ represents arithmetic growth,where only one daughter cell continues to divide while the other differentiates and matures. This results in a linear increase in growth.
$P$ represents geometric growth,where both daughter cells continue to divide,leading to an exponential increase in the number of cells.

(A) In arithmetic growth,the rate of growth is constant,and it is expressed as $L_t = L_0 + rt$,where $L_t$ is the length at time $t$,$L_0$ is the length at time $0$,$r$ is the growth rate,and $t$ is the time.
In geometric growth,both offspring cells retain the ability to divide,leading to an exponential increase in growth,expressed as $W_1 = W_0 e^{rt}$,where $W_1$ is the final size,$W_0$ is the initial size,$r$ is the relative growth rate,$t$ is the time,and $e$ is the base of natural logarithms.

(A) Geometric growth is characterized by a sigmoid or $S$-shaped curve when plotting the size or weight of an organ against time.
This growth pattern includes a lag phase (slow growth),an exponential or log phase (rapid growth),and a stationary phase (growth slows down and stops).
Arithmetic growth,on the other hand,produces a linear graph when plotting size against time.

(B) In arithmetic growth,only one daughter cell continues to divide while the other differentiates and matures. The mathematical expression for this is $L_t = L_0 + rt$,where $L_t$ is length at time $t$,$L_0$ is length at time zero,and $r$ is the growth rate. This equation represents a linear relationship,resulting in a straight-line graph when length is plotted against time.

(B) The figure illustrates geometric growth. In geometric growth,all cells or progeny of the mitotic division retain the ability to divide and continue to do so. As a result,the number of cells increases exponentially,which is characteristic of early embryonic development and growth in many plant tissues.

(D) Absolute growth is the total growth of a system per unit time. Here,the leaf grows from $5 \, cm^2$ to $10 \, cm^2$,so the absolute growth is $10 \, cm^2 - 5 \, cm^2 = 5 \, cm^2$.
Relative growth is the growth per unit time expressed on a common basis (initial size). It is calculated as: $\text{Relative growth} = \frac{\text{Absolute growth}}{\text{Initial size}} \times 100$.
Relative growth = $\frac{5 \, cm^2}{5 \, cm^2} \times 100 = 100 \%$.
Therefore,the absolute growth is $5 \, cm^2$ and the relative growth is $100 \%$.

(B) Absolute growth is the total growth of a system per unit time. Here,the initial area is $50 \, cm^2$ and the final area is $55 \, cm^2$.
Absolute growth = $55 \, cm^2 - 50 \, cm^2 = 5 \, cm^2$.
Relative growth is the growth per unit time expressed on a common basis (initial size).
Relative growth = $\frac{\text{Absolute growth}}{\text{Initial size}} \times 100 = \frac{5 \, cm^2}{50 \, cm^2} \times 100 = 10 \%$.
Therefore,the absolute growth is $5 \, cm^2$ and the relative growth is $10 \%$.

(C) Plant growth is a complex process that requires a variety of environmental and internal factors to occur effectively.
$1.$ Water: Essential for cell enlargement,turgidity,and as a medium for enzymatic activities.
$2.$ Oxygen: Required for aerobic respiration,which provides the energy $(ATP)$ needed for growth.
$3.$ Nutrients: Macro and micronutrients are necessary for the synthesis of protoplasm and structural components.
$4.$ Temperature: Enzymes involved in metabolic processes have optimal temperature ranges for activity.
$5.$ Light: Crucial for photosynthesis (in green plants) and photomorphogenesis.
$6.$ Gravity: Influences the direction of growth (gravitropism) in roots and shoots.
Therefore,all the listed factors $(I, II, III, IV, V, VI)$ are essential for the growth and development of plants.

(C) Growth is defined as an irreversible permanent increase in size of an organ or its parts or even of an individual cell.
In the case of a pollen tube,growth is characterized by the elongation of the tube as it travels through the style towards the ovary.
Therefore,the growth of the pollen tube is primarily measured in terms of its increase in length.

(A) In arithmetic growth,only one daughter cell continues to divide while the other differentiates and matures. The mathematical expression for arithmetic growth is $L_t = L_0 + rt$,where $L_t$ is the length at time $t$,$L_0$ is the length at time $0$,and $r$ is the growth rate/elongation per unit time. This equation represents a linear relationship between growth $(L_t)$ and time $(t)$. Therefore,when plotting growth against time,it results in a linear graph.

(D) The given curve represents a sigmoid growth curve,which is characteristic of growth in many biological systems.
It consists of three distinct phases:
$1$. Lag phase: The initial phase where growth is slow.
$2$. Exponential (or Log) phase: The phase where growth is rapid.
$3$. Stationary phase: The final phase where growth slows down and eventually levels off as resources become limited.
In the provided diagram,$P$ represents the final plateau region where the growth rate decreases and stabilizes,which is known as the stationary phase.

(D) In the exponential growth equation $w_1 = w_0 \cdot e^{rt}$,the term $r$ represents the growth rate.
It is defined as the relative growth rate because it measures the growth of the plant per unit time relative to the initial size.
It also indicates the ability of the plant to produce new plant material,which is why it is often referred to as the efficiency index.
Since all three descriptions ($A$,$B$,and $C$) correctly define $r$,the correct option is $D$.

(D) Root elongation typically follows an arithmetic growth pattern,where the growth rate is constant over time.
In arithmetic growth,the mathematical expression is $L_t = L_0 + rt$,where $L_t$ is the length at time $t$,$L_0$ is the initial length,and $r$ is the growth rate.
Statement $a$ is true because the rate of elongation is constant.
Statement $c$ is true because root elongation is a classic example of arithmetic growth.
Statement $b$ is false because the equation $W_t = W_0 e^{rt}$ represents geometric (exponential) growth,which is characteristic of cell division,not the linear elongation of roots.
Therefore,both $a$ and $c$ are true.

(A) During the phase of cell enlargement,the plant cell needs to increase its volume and turgor pressure.
To achieve this,the cell accumulates solutes (such as sugars and ions) in its vacuole.
This increase in solute concentration lowers the water potential inside the cell,which creates a gradient that favours the movement of water into the cell from the surrounding environment.
This process of water moving into the cell is known as endosmosis.
Consequently,the increased turgor pressure helps in the expansion and enlargement of the cell wall.

(A) The efficiency index of growth in plants is a measure of the ability of a plant or its parts to produce new plant material.
It is defined as the ratio of the final size to the initial size of the plant or its parts.
Mathematically,it is expressed as the rate of growth per unit initial parameter.
Therefore,it represents the total increase in growth per unit time relative to the initial amount of growth material.

(D) In the formula $L_t = L_0 + rt$:
$L_t$ represents the length at time '$t$'.
$L_0$ represents the length at time 'zero'.
$r$ represents the growth rate.
$t$ represents the time of growth.

(D) In geometric growth,each cell divides mitotically into two daughter cells. Both daughter cells continue to divide and redivide repeatedly.
Following the formula $2^n$,where $n$ is the number of mitotic divisions:
- After $1$ mitotic division: $2^1 = 2$ cells.
- After $2$ mitotic divisions: $2^2 = 4$ cells.
- After $3$ mitotic divisions: $2^3 = 8$ cells.
- After $4$ mitotic divisions: $2^4 = 16$ cells.
Therefore,after four successive mitotic divisions,$16$ cells will be produced.

(D) In arithmetic growth,the rate of growth is constant.
After each mitotic division,one daughter cell remains meristematic (continues to divide),while the other daughter cell undergoes differentiation and maturation,thereby losing its ability to divide.
Therefore,after $1$st division,$1$ cell differentiates.
After $2$nd division,another $1$ cell differentiates (total $2$).
After $3$rd division,another $1$ cell differentiates (total $3$).
After $4$th division,another $1$ cell differentiates (total $4$).
Thus,after $4$ successive mitotic divisions,the total number of cells that have lost the ability of cell division is $4$.

(D) Statement $i$ is correct: Plants require both macroelements and microelements for essential metabolic activities and growth.
Statement $ii$ is incorrect: The optimum temperature for the growth of most plants typically ranges between $25^{\circ} C$ and $35^{\circ} C$,not $15^{\circ} C-25^{\circ} C$.
Statement $iii$ is incorrect: Respiration is an oxygen-dependent process in aerobic plants; in the absence of oxygen,aerobic respiration cannot occur,and energy release is severely limited.
Statement $iv$ is correct: Gravitropism (or geotropism) is the growth of plant parts in response to gravity,determining the downward growth of roots and upward growth of shoots.
Statement $v$ is correct: Light is a critical factor for photosynthesis and acts as a signal for the germination of photoblastic seeds.
Therefore,statements $i, iv,$ and $v$ are correct.

(D) The Relative Growth Rate $(RGR)$ is calculated as the ratio of growth per unit time to the initial size,expressed as a percentage.
Formula: $RGR = \frac{\text{Final Size} - \text{Initial Size}}{\text{Initial Size}} \times 100$.
For leaf $X$: Initial size = $50 \ cm^2$,Final size = $100 \ cm^2$. $RGR = \frac{100 - 50}{50} \times 100 = \frac{50}{50} \times 100 = 100\%$.
For leaf $Y$: Initial size = $50 \ cm^2$,Final size = $55 \ cm^2$. $RGR = \frac{55 - 50}{50} \times 100 = \frac{5}{50} \times 100 = 10\%$.
Therefore,the $RGR$ of leaf $X$ and $Y$ are $100\%$ and $10\%$ respectively.

(B) During the exponential growth phase,the rate of growth is maximum.
Cells produced by the meristematic phase absorb water,become turgid,and undergo rapid expansion.
This process involves the synthesis of new cell wall materials and protoplasm,which results in maximum cell elongation.

(A) In arithmetic growth,only one daughter cell continues to divide while the other differentiates and matures. The mathematical expression is $L_t = L_0 + rt$,which represents a linear growth curve.
In geometric growth,both daughter cells resulting from mitosis continue to divide. This leads to an exponential increase in the number of cells,represented by the formula $W_1 = W_0 e^{rt}$,which results in a sigmoid or exponential curve.
Therefore,both Statement $I$ and Statement $II$ are correct.

(A) The term "Grand period of growth" was coined by Julius von Sachs.
It refers to the total time period during which the maximum rate of growth occurs, encompassing all phases of growth from initiation to maturation.

(D) Determinate growth refers to growth that stops after a certain size or stage is reached.
In plants,vegetative structures like roots,stems,and branches exhibit indeterminate growth because they possess meristems that allow for continuous growth throughout the life of the plant.
In contrast,reproductive structures like flowers and fruits exhibit determinate growth,as they grow to a specific size and then stop growing or mature.
Therefore,among the given options,the fruit is the correct answer.

(A) In the provided diagram,the phase labelled as $M$ represents the geometric phase of growth. In this phase,both daughter cells resulting from mitosis retain the ability to divide and continue to do so,leading to an exponential increase in cell number.
The phase labelled as $N$ represents the arithmetic phase of growth. In this phase,following mitotic cell division,only one daughter cell continues to divide while the other differentiates and matures,resulting in a linear increase in cell number.

(C) During the elongation phase of plant growth,cells undergo significant enlargement,increased vacuolation,and new cell wall deposition. As the vacuole grows in size,the cytoplasm is pushed towards the periphery,causing the nucleus to become peripheral and less conspicuous. Therefore,having large,conspicuous nuclei is not a characteristic of cells in the elongation phase.