Endosperm

What is Endosperm?

Endosperm refers to a kind of tissue that is developed inside the seeds of flowering plants, the majority of them after fertilisation 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:

• It is the source of nutrients powering embryo development.

• It also participates in seed formation and seed dispersal.

• It is central to the flowering plant's reproductive success and evolutionary adaptation.

Also Read:

• Endosperm : Its Development and Significance MCQ

• Embryogeny in Monocots

• Events in the Germination of Pollen Grains

Structure And Types Of Endosperm

Endosperm is a tissue that stores food for the growing embryo in seeds. 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 through 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 is present in plants such as monocotyledons, for example, Alismataceae.

Formation And Development Of Endosperm

The development of endosperm starts with double fertilisation, which consequently triggers the formation of the primary endosperm nucleus. The primary endosperm nucleus divides many times to form the endosperm tissue. This tissue stores food and helps the embryo grow properly inside the seed.

Double fertilisation

• 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.

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 nucleus

• Cellularization: Cell walls begin to appear around nuclei, giving them 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 plays a key role in seed germination. It provides food, support, and signals to help the embryo grow. Endosperm carries out various important roles in growing and germinating seeds. Some of the functions of endosperm are given below:

Nutrient Storage

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

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

Support for 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 dicotyledonous and monocotyledonous seeds. Some examples of different endosperms in different plant species are given below:

• 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 the seedling

Differences Between Endosperm In Monocots And Dicots

Endosperm Genetic And Molecular Aspects

Endosperm development is controlled by genes and plant hormones. These signals help the endosperm grow properly and support the embryo. The formation and activity of the endosperm are regulated by complex genetic and hormonal interactions as given below:

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 plant 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 is very important in agriculture and the food industry. It provides nutrients like starch and is used to improve crop quality and nutrition through breeding and agriculture biotechnology . Endosperm finds huge applications in food industries and agriculture are given under:

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

Sometimes, endosperm does not develop properly, leading to poor seed growth. These abnormalities can be caused by genetic mutations or environmental stress. 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.

MCQs on Endosperm

Question 1: The morphological nature of the edible part of coconut is:

1. Perisperm

2. Cotyledon

3. Endosperm

4. Pericarp

Answer: Free-nuclear endosperm refers to a stage in the development of endosperm where successive nuclear divisions occur without the formation of cell walls, resulting in the presence of multiple free nuclei in the endosperm. This stage is characterized by the nuclei freely floating in the cytoplasm. An example of free-nuclear endosperm is the coconut water from a tender coconut, which is essentially the liquid endosperm containing these free nuclei before it eventually solidifies into the mature endosperm (the white part of the coconut).

Hence, the correct answer is option 3) Endosperm

Question 2: If the diploid number of a flowering plant is 36. What would be the chromosome number in its endosperm?

1. 36

2. 18

3. 54

4. 72

Answer: The endosperm is a product of triple fusion. One male nucleus (n=18) fuses with a diploid secondary nucleus (2n=36), and it becomes 3n=54. It forms as a result of triple fusion, where one male gamete (n = 18) fuses with the diploid central cell (2n = 36) in the embryo sac, resulting in a triploid nucleus (3n = 54).

Hence, the correct answer is option 3) 54.

Question 3: Perisperm differs from endosperm in:

1. Its formation by fusion of secondary nucleus with several sperms

2. Being a haploid tissue

3. Having no reserve food

4. Being a diploid tissue

Answer: The ploidy level and origin are the only differences between the perisperm and the endosperm. Perisperm is a diploid tissue (2n), which is the product of nucellus before fertilization, providing a food reserve for the embryo. The endosperm is triploid (3n), as it is developed after fertilization through a mechanism called double fertilization, where a sperm cell combines with two polar nuclei. Such a difference highlights their roles during seed development and nutrition.

Hence, the correct answer is Option 4) being a diploid tissue.

Question 4: Which of the following statements about endosperm development is true?

1. Endosperm development precedes embryo development.

2. Endosperm is triploid in all angiosperms.

3. The primary endosperm cell forms a diploid endosperm tissue.

4. Endosperm provides nutrition to the developing embryo.

Answer: Endosperm development occurs before embryo development. Following fertilization, the primary endosperm cell divides repeatedly to generate endosperm tissue. Endosperm tissue is triploid, which means it has three sets of chromosomes. Endosperm tissue cells are loaded with reserve food components like as carbohydrates and proteins, which provide sustenance to the developing embryo. Until the embryo can create its food delivery system, the endosperm provides vital nutrients for its growth and development.

Hence, the correct answer is option 4) Endosperm provides nutrition to the developing embryo.

More useful resources:

Recommended Video On 'Endosperm'