Endosperm

Definition Of Endosperm

Endosperm refers to a kind of tissue which is developed inside the seeds of flowering plants, the majority of them after fertilization has occurred. This tissue encapsulates the embryo and provides it with nutrition in the form of starches, proteins, and oils, which facilitate its development and seed germination.

Role Of Endosperm In Plant Biology

It is the source of nutrition powering embryo development. It also participates in seed dispersal and viability; therefore, it is central to the flowering plant's reproductive success and evolutionary adaptation.

Structure And Types Of Endosperm

The endosperm structure varies in different plant species and is differentiated based on how its cellular development takes place.

Cellular Endosperm

• The development takes place by the cell division of the primary endosperm nucleus.

• After every division, cytokinesis takes place and a cellular structure develops.

• This type is prevalent in plants of Datura and Petunia.

Nuclear Endosperm

• The primary endosperm nucleus divides several times without cytokinesis and results in a multinucleate structure.

• Later cellularisation takes place around each nucleus.

• Plants having this type of endosperm are Maize and wheat.

Helobial Endosperm

• It is the fusion of cellular and nuclear types.

• A cell division primarily leads to the formation of two regions: one undergoing nuclear type development and the other cellular type.

• Distribution Present in plants such as monocotyledons, for example, Alismataceae.

Formation And Development Of Endosperm

The development of endosperm starts with double fertilization, which consequently triggers the formation of the primary endosperm nucleus.

Double fertilization

• It is the process by which one sperm nucleus combines with the egg cell to form the zygote.

• The other sperm nucleus fuses with two polar nuclei to become the triploid primary endosperm nucleus.

• The embryo develops with the endosperm development.

Primary Endosperm Nucleus

• The triploid primary endosperm nucleus divides mitotically.

• Starts to develop the endosperm tissue that will feed the developing embryo.

Stages In The Development Of Endosperm

• Free nuclear stage: More than one free nuclei

• Cellularization: Cell walls begin to appear around nuclei, giving it a cellular nature.

• Maturation: The accumulation of nutrients with their structural changes within the seed allows the seed to be ready to germinate.

Functions Of Endosperm

Endosperm carries out various important roles in growing and germinating seeds.

Nutrient Storage

• Starch, proteins, and oils are stored as reserve food material.

• A steady supply of nutrients to the growing embryo is provided.

Support To Embryo Development

• The embryo is surrounded and cushioned by the endosperm.

• Supplies hormones and growth regulators.

Role In Seed Germination

• Stored nutrients are broken down during germination.

• Fuels the initial growth until the seedling can photosynthesize.

Endosperm In Different Plant Species

Endosperm structure and function may differ quite drastically between monocot and dicot plants.

Monocots Vs. Dicots

• Monocots: The endosperm persists and serves as the primary source of nutrients at germination, for example, Rice, Wheat

• Dicots: During seed development, the endosperm is absorbed by cotyledons, for example, Beans, Castor

• Examples: Rice, Wheat, Coconut, Castor

• Rice and wheat: The endosperm persists as a significant part of the seed.

• Coconut: Liquid endosperm that is coconut water; solid endosperm, the coconut meat.

• Castor: Endosperm is rich in oil and it's essential for the development of seedling

Differences Between Endosperm In Monocots And Dicots

Genetic And Molecular Aspects

The formation and activity of the endosperm are regulated by complex genetic and hormonal interactions.

Genetic Control Of Endosperm Development

• It requires specific profiles of gene expression

• It involves epigenetic modulations as well

Hormones In The Development Of Endosperm

• Auxins, cytokinins, and gibberellins regulate the growth and development of the endosperm.

• The balance of hormones is an essential prerequisite for the normal functioning of the endosperm

Commercial And Agricultural Significance

Endosperm finds huge applications in food industries and agriculture.

Endosperm In The Food Industry

• Source of carbohydrates. For example, flour from wheat

• Taken in a variety of foodstuffs

Effects On Crop Yield And Quality

• The quality of endosperm determines seed weight and nutritional value.

• Breeding programs target the improvement of characteristics relating to endosperm.

Role In Biotechnology

• For example, the "Golden Rice"

• Genetic modification for improved nutritional value

• Golden rice: Endosperm enriched with Vitamin A.

Endosperm Abnormalities

Abnormal development of endosperm results in defective seeds having reduced viability.

• Faulty cellularization

• Dwarfism and weak growth.

• Causes and Implications

• Mutation of genes

• Stress due to environmental factors.

Examples Of Common Abnormalities

• Chalky endosperm in rice.

• Shrunken endosperm in maize.

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