Plant Development: Definition, Stages, Principles, Topics, Importance

What Is Plant Development?

Plant development is a series of processes where the growth and maturation of a plant take place—germination, growth, differentiation, and reproduction. Knowledge of plant development is important since it stirs the unraveling of ways that plants modify themselves in adapting to the environment, optimize resource use, and contribute to ecosystems. This is key to future advances in agriculture, horticulture, and conservation. The plant's life cycle includes seed germination, vegetative growth, flowering, pollination, seed formation, and dispersal—processes crucial for species survival and continuation.

Embryogenesis in Plants

The details of embryogenesis are given below:

Definition

The zygote divides many times, forming a multicelled embryo which further differentiates into basic structures such as the shoot apical meristem, root apical meristem, and cotyledons.

Stages of Embryo Development

1. Zygote: The zygote divides unequally to form an embryo.

2. Proembryo: Repeated cell divisions form a multicellular proembryo.

3. Globular Stage: Embryo becomes spherical, and primary meristem layers differentiate.

4. Heart Stage: Two cotyledons appear, giving the embryo a heart shape.

5. Torpedo Stage: Embryo elongates into a torpedo shape, vascular tissues develop.

6. Mature Embryo: Fully developed embryo with cotyledons, radicle, and plumule forms..

Seed Germination – Start of New Growth

The details of seed germination are given below:

Conditions Required

Seed germination is dependent on the presence of adequate moisture, temperature, oxygen, and in some cases light. These conditions trigger the metabolic pathways of the seed to start growth.

Types of Germination

• Epigeal Germination: epicotyl elongates and brings up the cotyledons above the soil surface (for example beans).

• Hypogeal Germination: the hypocotyl elongates and pushes the shoot apex with cotyledons above the soil surface (for example peas).

Vegetative Growth

The details of vegetative growth are given below:

Root Development

Roots arise from the root apical meristem and are mainly and secondarily responsible for mechanical support for the growing plant body as well as being sites where water and nutrient uptake for the plant body occurs.

Shoot Development

Shoots arise from the shoot apical meristem and are mainly pedicled and stemmed that accommodate the leaf blades and florets.

Leaf Development

Leaves arise from leaf primordia in the apical bud of a shoot. experience morphogenesis and shifts producing horizontal, long/oval/spear/cordate-heart shapes, and many produce characteristic structures for photosynthesis.

Reproductive Development

The details of reproductive development are given below

Flower Formation

The flowers originate with floral meristems that get transformed through a series of gene-regulated processes into sepals, petals, stamens, and carpels.

Pollination

Pollination refers to the transfer of pollen from the male anthers to the female stigma. This transfer may be effected by wind, water or by the actions of conduction agents—pollinators such as insects or birds.

Fertilization

Fertilization takes place as the pollen tube elongates down the style. Sperm cells fuse with the egg cell of the ovule; each sperm cell unites with an egg, forming a zygote.

Fruit and Seed Formation

After pollination, the ovary after fertilization develops into a fruit and the ovules and ovaries into the seed. Seed maturation and seed dispersal are also a part of this step.

Hormonal Regulation Of Plant Development

The role of hormones is described below:

Auxins

• Auxins are important in controlling cell elongation, apical dominance, and root development.

• Most of the auxins are synthesised in the shoot apical meristem and unfolding leaves.

• The auxins are also involved in the regulation of phototropism and gravitropism; hence, they act by controlling the direction of growth either towards the source of light or against gravity.

• The role of auxins is also vital in vascular differentiation as well as fruit development.

Gibberellins

• Gibberellins promote stem elongation, and germination of seeds, and enhance flowering.

• Gibberellins play an important role in breaking seed dormancy and stimulating germination.

• They stimulate the seed embryo to produce the enzymes that translocate the food reserve stored in the seed to the growing area.

• Gibberellins promote an increase in cell division while the division of cells and elongation play the role of growing plant mass.

Cytokinins

• Cytokinins promote cell division, and cell differentiation, and lead to the mobilization of nutrients.

• Cytokinins also delay the aging process of the leaves.

• Acting with auxins: During organogenesis, cytokinins work combinatorially with auxins to regulate the development of the shoot and the root system.

• Cytokinins are mainly synthesised in the root and are then transferred to the plant.

Ethylene

• Ethylene is a gaseous hormone that mediates pathways in processes such as fruit ripening, leaf abscission, and stress.

• This includes the control of senescence, inhibition of stem elongation, and formation of root hair.

• Its response to mechanical stress, e.g. bending or wounding, is also vital to plant adaptation.

Abscisic Acid

• Abscisic acid (ABA) is predominantly stress-related and controls the closing of stomata to prevent the loss of water.

• It induces seed dormancy to prevent seed germination with unfavourable conditions.

• It also ensures the regulation of plant growth stops, wherein cell division and elongation are prevented under adverse conditions to the plant.

Environmental Factors Influencing Plant Development

The environmental factors are:

Light (Photoperiodism)

• Photoperiodism is the ability of a plant to respond to the relative lengths of the darkness and light periods.

• Photoperiodism controls the flowering, seed germination and vegetative growth of plants.

• Based on the photoperiodic response in the flowering of plants, plants are classified into three types of plants, namely, short-day, long-day, and day-neutral plants.

• Light quality, light intensity and duration affect photosynthesis, photomorphogenesis and circadian rhythms in the plants.

Water

• Water is an essential component of growth because of its dissolving power, a reagent in biochemical reactions, and its carrying of nutrients.

• Adequate water provided results in turgor— the pressure against the cell wall— which is required to produce cell expansion and therefore growth.

• Water deficiency or drought conditions can invoke a response to close the stoma, and stop photosynthesis and growth and too much water may also lead to hypoxia in the root, causing a reduction in nutrient uptake.

Temperature

• Temperature determines how fast biochemical reactions occur and, in general, plant metabolism.

• There are temperature ranges favouring seed germination, enzyme activities, and growth processes in an optimum way.

• More than adequate or extreme temperatures when owing to the rise in temperature, give rise to heat stress or because of frost, affect plant morphology, physiology, and yield.

• Critical processes are done in some species, and this is done in subjects during vernalisation, for instance, exposing the plants to long coldness to be able to induce flowering.

Soil Nutrients

• Soil nutrients are such an important factor needed for the growth and development of plant life

• These are the macronutrients, such as nitrogen, phosphorus, and potassium, and micronutrients, such as iron, manganese, zinc.

• Mainly essential for myriad physiological and biochemical functions.

Plant Development NEET MCQs (With Answers & Explanations)

Important topics for NEET are:

• Stages embryogenesis in Plants

• Hormonal regulation

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. Hypertrophy 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 Plant Development

• Plant Hormones

• Auxin Biosynthesis

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