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

Definition Of 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 unravelling 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.

Phases Of Plant Development

Embryogenesis begins with ovule fertilisation and ends with zygote formation.

Embryogenesis

Stages of Embryo Development

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.

Seed Germination

Conditions Required for Germination

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 Seed 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

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

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:

Role Of 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.

Role Of 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.

Role Of Cytokinins

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

• Cytokinins also delay the ageing 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.

Role Of Ethylene

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

Role Of 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.

Recommended video on "Plant Development"