Phases of growth in plants: Definition, Process & Phases

What Are the Phases of Plant Growth?

Plant growth refers to the process involved in increasing the number of cells in the plant body. It is a general, progressive development of the plant. Understanding the phases of growth will enable farmers to know at which time to apply a given practice for maximum results, that is, obtaining yields from crops and also for good health of the plants.

The major growth stages are seed germination, which consists of a seed sprouting to become a seedling; vegetative growth, where there is the development of leaves, stems, and roots and reproductive growth, marked by flowering, fruiting, and formation of seeds. Each of the phases is influenced by different internal and external factors. Being able to recognize these stages helps manage plants effectively for productivity.

Germination – The First Growth Phase

The first stage is germination and is explained below:

Definition & Importance

Germination is the process whereby a seed develops into a new plant. It initiates the plants’ life cycle, hence, it assures continuity.

Stages of Germination

• Imbibition: This is the first stage where the seed has imbibed water to expand and soften, hence initiating the trigger of metabolic processes.

• Enzyme activation: Upon rehydration, the enzymes become active to hydrolyze stored food materials in the seed for energy and nutrient supply to the developing embryo from the seeds.

Vegetative Growth – Root, Stem & Leaf Development

This period of vegetative growth involves root growth, stem elongation, and leaf expansion.

Definition

Vegetative growth is the growth stage of a plant during which it increases in size and mass through the formation of roots, stems, and leaves. This period is of particular importance in setting the general structure of a plant and for peak photosynthetic potential.

Processes

• Root development: These roots elongate and branch to anchor the plant and absorb water and nutrients from the soil.

• Stem elongation: The stem will elongate to support leaves and flowers, and transportation of nutrient water between the roots and leaves.

• Leaf expansion: Leaves increase in size to expand photosynthesis which provides energy to the plants.

Factors Affecting Vegetative Growth

• Light: This factor is very crucial for photosynthesis and generally for good plant conditions.

• Water: Adequate water must be available for the transportation of nutrients, turgor pressure, and maintaining the shape and biochemical reactions.

• Nutrients: The essential nutrients, both macro- and micro-requirement are very critical for the growth and development of plant tissues.

Budding – Initiation of New Shoots & Structures

Budding is a process by which new structures in plants, leaves, flowers, or shoots grow from buds.

Types of Buds

There exist mainly two types of buds, namely the terminal and axillary.

• Terminal buds applies to those at the tips of stems

• Axillary buds are those at the point on the stem where the leaf joins.

Role in Development

It caters to the growth and reproduction of a plant. Thus, the terminal buds lead to vertical growth and elongation of the plant, while axillary buds result in branching and new shoots. In this way, it contributes to the structure of the plant, enhancing its possibilities for photosynthesis and hence, reproduction.

Flowering – Transition to Reproductive Phase

Flowering is the process by which plants form flowers. The reproductive structures are not dispensable in sexual reproduction. It is a very important process in the generation of fruits and seeds, thus in the survival of a plant species.

Flower Development

• Bud formation: Stage at which flower buds have formed from the meristematic tissues.

• Blooming: This is the time or process that flowers open up to expose their reproductive organs to the outside environment.

• Pollination: This is the transfer of pollen from the anther (male) into the stigma, the female part, for fertilization to occur.

Factors Influencing Flowering:

• Temperature: Many plants require specific temperatures for flowers to form.

• Light duration: Photoperiod, the length of day or night, controls the time of flowering in many species. Some have to be grown for a long day, whereas others may require a short day.

Fruit And Seed Development

Fruit and seed development is the process following fertilization whereby the transformation of the ovary to a fruit and seeds mature therein. This process offers protection, nourishment, and dispersal of seeds to ensure the propagation of the plant species.

Stages of fruit development

• Fruit growth: This is the stage in which fruit grows in size by cell division and cell expansion.

• Ripening: This is the final stage of the process when the fruit has matured, softened and, in most cases, become sweeter and more palatable. There will be a change in colour in some cases.

Seed formation and dispersal mechanisms

Seeds form within the fruit and contain the embryo with some stored nutrients, while the dispersal mechanisms are wind, water, animals, and self-ejection that help scatter the seeds around to new growing locations

Growth Rates – How Fast Plants Grow

Growth rates refer to the speed by which a plant grows through different stages of its life cycle. Usually measured in height, biomass, and leaf area over time

Factors Affecting Growth Rate

• Genetics: Growth potential is inherent due to the species and cultivar of the plant.

• Environmental conditions: Light, temperature, water, nutrients

• Soil Quality: This includes soil fertility, pH levels, structure and component of soil.

• Diseases: Pests and other stress factors are not present in the plants.

Growth Rate Pattern

• During the germination period growth is slow as the seedling gets established.

• An increase in size and biomass happens rapidly is seen in vegetative phase.

• As the resources are partitioned for flower and fruit production, the growth rate slows down in the reproductive phase.

• Monitoring is the process of observing and measuring anything regularly. This optimises growing conditions to raise the productivity of plants.

Conditions For Plant Growth

The conditions required for plant growth

Environmental Factors

• Light: This factor is responsible for photosynthesis and controls flowering and growth.

• Water: It is necessary for nutrient transportation and for carrying out cellular changes; it provides turgor pressure to the plants.

• Temperature: It controls the rates of enzymatic reaction and growth; the optimum temperature range varies from species to species.

• Soil: It provides nutrients and physical support; it has a profound effect on root development and water-holding capacity due to its quality, particularly the pH and structure.

• Nutrients: Essential macronutrients and micronutrients; balanced soil fertility is the key.

Internal Factors

• Genetic Makeup: It provides for growth potential and environmental adaptation.

• Hormones: These are responsible for the control of cell division, elongation, and all other procedures. The main important hormones include auxins, gibberellins, and cytokinins.

• Water Status: This provides for cell turgor, gives the force for growth, and requires proper uptake and transport.

• Nutrient Status: Maintaining properly balanced levels of internal nutrients to sustain metabolic functions

• Age and Developmental Stage: Rates and needs vary at the life stages of a plant- seedling, vegetative, and reproductive.

Phases of Growth NEET MCQs (With Answers & Explanations)

Important topics for NEET are:

• Phases of Growth

• Conditions for Plant Growth

Practice Questions for NEET

Q1. The phase of growth where the cell wall starts accumulating new material is known as

1. Phase of cell formation

2. Phase of elongation

3. Phase of differentiation

4. Primary growth

Correct answer: 2) Phase of elongation

Explanation:

The phase denoted as the "elongation" or "expansion phase" in the cell cycle is a critical period where new substances are integrated into the cell wall, predominantly observed in plant cells during interphase. Key aspects include the synthesis of cell wall components such as cellulose, hemicellulose, and pectin, which facilitate cell enlargement post-mitosis. This phase typically transpires in the G1 or G2 phase, with cellulose deposition and turgor pressure playing pivotal roles in overall plant growth.

Hence, the correct answer is option 2) Phase of elongation.

Q2. The cells in watermelon may increase in size by up to 3,50,000 times. This phenomenon is called

1. Hypotrophy

2. Hypertrophy

3. Hyperplasia

4. Hypoplasia

Correct answer: 2) Hypertrophy

Explanation:

Hypertrophy is the increase in the size of cells leading to the enlargement of a tissue or organ. HypertrophyHypertrophy typically occurs as a response to increased demand or stress. For instance, muscle hypertrophy takes place when muscle fibres grow larger due to exercise, especially through strength training. While physiological hypertrophy is generally healthy, pathological hypertrophy, such as that occurring in the heart due to high blood pressure, can impair function and lead to complications.

Hence, the correct answer is option 2) Hypertrophy

Q3. Growth can be measured in various ways. Which of these can be used as parameters to measure growth?

1. Increase in cell number

2. Increase in cell size

3. Increase in length and weight

4. All of the above

Correct answer: 4) All of the above

Explanation:

Generally speaking, plant growth is indeterminate; plants can continue to develop for the duration of their lives. This is because specific parts of their bodies contain meristems, which have the capacity to divide and reproduce themselves. The open form of growth refers to the process by which the meristem's activity continuously adds new cells to the plant body. Growth Is Measurable: Growth at the cellular level results from an increase in protoplasm, which is hard to quantify. Plant growth is quantified using a variety of techniques, such as a rise in fresh weight, volume, dry weight, or cell number. The apical meristem of a single maize root can produce more than
The growth can be in lateral or apex regions and can cause an enlargement in height or weight; all of these changes are collectively termed growth.

Hence, the correct answer is option 4) All the above.

Also Read:

• MCQs on Phases of Growth

• Plant Hormones

• Auxin Biosynthesis

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