Arithmetic and geometric Growth In plants : Plant Growth and Development: definition, notes, overview, Factors

What Is Plant Growth?

Plant growth refers to an increase in the size and mass of a plant over time and involves cell division, cell enlargement, and cell differentiation. This is very important in understanding development, productivity, and adaptability in plants under biology and ecology.

Growth can be divided into two: arithmetic growth where plants increase in size by a constant amount per unit of time and geometric growth sees an exponential increase in the rate of growth, sometimes found in rapidly growing populations or under optimum conditions.

Arithmetic Growth – Definition & Characteristics

Arithmetic growth is explained below:

Definition

In arithmetic growth, the growth of plants is by an increase in size or mass at a constant rate. As such, every unit of time will always cause an increase in growth of a fixed amount that results in linear growth.

Characteristics

Arithmetic growth refers to the increase in size or biomass at a constant or linear rate. It almost always takes place under conditions of a relatively stable environment wherein the factors required for growth are continuously available, leading to a predictable and incremental rise in the parameters of growth.

Examples

The examples of arithmetic growth in plants are:

Example 1: Leaf development

In some species of plants, leaf development offers an excellent example of arithmetic growth, each successive leaf of a plant is a fixed amount larger than the last one.

Example 2: Root growth in certain conditions

Under adequate conditions, with adequate water and nutrients, the growth of roots may follow arithmetic patterns. In other words, a root can elongate by a constant amount over time.

Geometric Growth – Definition & Characteristics

Geometric growth is explained below:

Definition

Geometric growth is a plant growth pattern whereby there is an increase in size or biomass with time at an increasingly faster rate. This usually involves doubling or increasing at a constant multiple over regular time intervals. Such kind of growth brings about an exponential relation of increase in size or population with time.

Characteristics

Geometric growth describes rapid increases in the growth rate, which are exponential. That is, each period of growth completes with a larger increment than the previous period. Thus, the growth curve is J-shaped. This can be observed in cases of optimum environmental conditions and sufficient resources.

Examples

The examples of the geometric growth in plants are:

Example 1: Population of plant seedlings

Only a few seeds, which have the potential to grow into seedlings under favourable conditions, would increase in population geometrically. The geometric progression of successive generations of seedlings raises the total number of plants.

Example 2: Vegetative reproduction

Plants which reproduce vegetatively by forming runners or tubers may grow geometrically. Thus, one strawberry plant may produce several runners that grow into new plants and before long the number of plants multiplies rapidly in a very short period.

Differences Between Arithmetic and Geometric Growth

The difference between arithmetic growth and geometric growth is included in the table below:

Significance of Arithmetic & Geometric Growth

The significance of arithmetic and geometric growth:

• Helps to understand the development stages.

• Important for calculating population dynamics.

• Used in crop modeling, forest resource management.

• Predicts the accumulation of biomass.

Arithmetic and Geometric Growth NEET MCQs (With Answers & Explanations)

Important topics for NEET are:

• Characteristics of Arithmetic and Geometric Growth
• Arithmetic vs Geometric Growth

Practice Questions for NEET

Q1. During the exponential phase of geometric growth,

1. Slow growth takes place

2. Rapid growth occurs

3. Growth stops

4. Growth is visible

Correct answer: 2) Rapid growth occurs

Explanation:

In most biological systems, the growth process begins with a slow phase called the lag phase. This is followed by a period of rapid growth, known as the log or exponential phase, where growth occurs at an exponential rate. However, as the supply of nutrients becomes limited, the growth rate slows down, leading to what is known as the stationary phase. When the growth of plants is plotted over time, the resulting graph typically produces an S-shaped or sigmoid curve, illustrating these distinct growth phases.

Hence, During the exponential phase of geometric growth, rapid growth takes place.

Hence, the correct option is 2) Rapid growth occurs.

Q2. Slow growth takes place in the

1. Log phase

2. Lag phase

3. Exponential phase

4. Linear phase

Correct answer: 2) Lag phase

Explanation:

Slow growth is characteristic of the lag phase within a growth curve.

Elaboration:
The lag phase is the preliminary stage of a microbial population's expansion, where the organisms are acclimatizing to novel environmental conditions. During this interval, cell division is negligible; however, substantial metabolic activity transpires. Microbial entities engage in the synthesis of essential enzymes, proteins, and other vital molecules that facilitate growth. Consequently, the growth rate is gradual, and the population does not undergo a substantial increase. This phase is pivotal for equipping the cells to enter the ensuing logarithmic (exponential) phase, where active cell division occurs.

Hence, the correct answer is option 2) Lag phase.

Q3. Geometric growth represents ____ graph. Choose the correct option to fill in the blank

1. J-shaped

2. S-shaped

3. Bell-shaped

4. Linear shaped

Correct answer: 2) S-shaped

Explanation:

Geometric growth is a term used to describe population growth over time, usually with several recognizably different stages:

1. Lag Phase: At first, the growth is slow because the population is adapting to its environment. In this phase, the individuals are settling down and resources are being used.

2. Log Phase (Exponential Phase): After the lag phase, growth becomes exponential and occurs rapidly. During this phase, the population size increases significantly due to the abundance of resources.

3. Stationary Phase: As the resources become scarce the growth slows down. The population size reaches stabilization with a balance between birth and death rates as there is no net increase in population.

When graphed against time, geometric growth shows an S-shaped curve, sometimes called a sigmoid curve. Such a curve portrays the slow, initial growth and then the sudden expansion that ultimately levels off with the population having reached carrying capacity.

Hence, the correct answer is option 2) S-shaped.

Also Read:

• MCQs on Arithmetic and Geometric Growth

• Plant Hormones

• Auxin Biosynthesis

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