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Endosperm Function & Types

Annakay Newell, Angela Lynn Swafford
  • Author
    Annakay Newell

    Annakay Newell has taught in the biological and environmental science fields for over ten years. She has a PhD in plant pathology from the University of Georgia, a MSc in plant pathology from the University of Arkansas and a BSc in Biology from the University of Arkansas Pine Bluff.

  • Instructor
    Angela Lynn Swafford

    Lynn has a BS and MS in biology and has taught many college biology courses.

Understand what an endosperm is through its definition and learn its important role in plants. Be familiarized with its different functions and various types. Updated: 12/02/2021

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What is Endosperm?

The endosperm is a tissue that surrounds the embryo of seeds in angiosperms and provides nutrition. Angiosperms are plants that produce flowers and seeds that are enclosed within a fruit. Gymnosperms is the other plant category that is used to characterize those that have no flowers or fruits, with seeds formed on the leaf surface. Angiosperms include fruits, grains, vegetables, and flowers. The seed in angiosperms consist of three distinct parts, the seed coat, endosperm, and embryo. The seed coat is the outer layer which protects the inner embryo from physical or microbial damage. The embryo is the immature fertilized ovule of the seed that will germinate to produce the seedling. The development of the embryo and endosperm are initiated by a double fertilization event that is unique to angiosperms. Double fertilization is so called because there is both fusion of a sperm with an egg and fusion of a sperm with two polar nuclei. The anatomy of angiosperms include:

  • Stamen- the reproductive organ of a flower that produces pollen.
  • Flower- the reproductive structure of flowering plants that facilitates the union of sperm and egg.
  • Carpel- female reproductive organ of the flower which consists of the ovary, stigma, and style.
  • Pollen- formed in the stamen and produces pollen grains and sperm cells that fertilize eggs.

Flower of an angiosperm

Angiosperm yellow hibiscus flower

Function of Endosperm

The function of the endosperm is three-fold. It plays a critical role in supplying nutrients for embryonic growth, controlling the growth rate of the embryo during germination and seed development, and providing some amount of protection for the embryo. However, the most important role in plants is as the baby plant's food source. Nourishment of the embryo is provided by the endosperm in the form of starch, proteins, and lipids.

The endosperm is also important to humans and other animals because it stores the seed reserves which act as a renewable source of food and is the main feed for livestock. For example, the grains of cereal crops are primarily endosperm with rice, wheat and corn being the three most important food crops for human consumption in the world. The endosperm of wheat is ground into flour for bread and other products.

Wheat grain is an important food source for humans and is primarily endosperm tissue

wheat grain is primarily endosperm

Types of Endosperms

There are three forms of endosperms in angiosperms which are classified according to the timing of cell wall formation and vary according to plant species. These include the nuclear, cellular and helobial endosperms. The triploid (containing three homologous sets of chromosomes) primary endosperm nucleus is formed from the fusion of the sperm nucleus with the polar nuclei. The primary endosperm nucleus then undergoes rapid mitotic divisions to form the endosperm tissue.

Nuclear

In nuclear endosperms, primary endosperm nuclear division and subsequent nuclear divisions are not coincident with cell wall formation. The cell wall is either formed after these free-nuclear divisions or the nuclei remain free in the cytoplasm.

Cellular

In cellular endosperms nuclear divisions and cell wall formation occur simultaneously and the endosperm has a cellular form from the initial stages.

Helobial

Helobial endosperms are common among monocotyledons, which are grass or grass-like plants with embryos that bear a single cotyledon (seed leaf). In this type of endosperm formation, the cell wall is inserted between the first two nuclei, with development occurring either along the nuclear or cellular pattern on each side. Helobial endosperm formation is therefore an intermediate of the nuclear and cellular types.

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Frequently Asked Questions

What is the function of an endosperm?

The function of the endosperm is three-fold. It plays a critical role in supplying nutrients for embryonic growth, controlling the growth rate of the embryo during germination and seed development, and providing some amount of protection for the embryo. However, the most important role in plants is as the baby plant's food source.

What is an endosperm in simple words?

The endosperm is a tissue that surrounds the embryo of seeds in angiosperms. It functions in providing nutrients for the embryo.

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