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ENDOSPERM.pptx

The document discusses endosperm, which is a nutritive tissue stored in seeds to provide nutrients for the embryo. There are three main types of endosperm based on development - nuclear, cellular, and helobial. Nuclear endosperm is the most common type and involves repeated nuclear division without cell wall formation initially. Cellular endosperm involves cell wall formation after each nuclear division. Helobial endosperm involves initial division into two cells like cellular endosperm, but further divisions are like nuclear endosperm. Endosperm can also have haustorial variations and can be ruminate, with an irregularly folded surface. Endosperm plays an important role in seed nutrition and development.

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ENDOSPERM Dr. V. Biligiriranga HOD PG Department of Botany
CONTENTS • Endosperm • Types Of Endosperm • Haustorial Variations • Ruminate Endosperm • Composite Endosperm
INTRODUCTION  Endosperm is a nutritive tissue stored in the seed for the embryo and it is formed by the fusion of one male gamete with the polar nuclei.  Endosperm plays a main role in the diet of human beings.  Endosperm is found in all angiosperms except few families like Orchidaceae, Podostemonaceae and Trapaceae.  The seeds without endosperm: Nonendospermous seeds or exalbuminous seed.  The seed containing the endosperm: Endospermous or albuminous seed.  Endosperm is replaced by fleshy cotyledons in dicotyledons.  In monocotyledons, endosperm persists in the mature seeds too and stores the food.  Endosperm tissue is rich in carbohydrates and also contains proteins and lipids.
Salient features of Endosperm • Endosperm development takes place from the triploid cell (3n) in the embryo sac. • The second male gamete fuses with the diploid secondary nucleus (formed by 2 polar nuclei) to form primary endosperm nucleus (PEN) and a triploid cell. The process is known as triple fusion • Endospermic cells are mostly triploid but in some plants, they may be diploid (water lily) or polyploid (up to 15n) • In some of the dicots, mature seeds contain food stored in the endosperm, they are called endospermic or albuminous seeds, e.g. castor • In beans, peas, gram seeds, the endosperm is completely absorbed during development and food is stored in two cotyledons. They are called exalbuminous seeds • Endosperm mostly contains starch as a food reserve, but it may contain fats, e.g. castor
• Endosperm provide nutrients to seeds during dormancy • Endosperm also contains certain hormones like cytokinins and helps in cell differentiation • In grains, like wheat, maize, barley, corn, the endosperm is the main source of food • The white flour, used to prepare bread, only contains endosperm of wheat seeds • The outer layer of endosperm is the aleurone layer. It secretes the amylase enzyme, which breaks down the starch contained in the endosperm to sugars for utilisation by seedlings • Orchid seeds lack an endosperm Coconut water is the example of a liquid endosperm
Types of Endosperm How the primary endosperm nucleus (PEN) develops into endosperm differs in various plants. Endosperms are divided into three main types based on their development pattern. 1. Nuclear Endosperm 2. Cellular Endosperm 3.Helobial Endosperm Of these three types, • nuclear endosperm is the most common and is found in about 56% families of angiosperms. • Cellular endosperms occurs in 25% families. • Helobial endosperm occurs in 19% families. • Furthure , cellular endosperm is mostly confined to dicotyledonous families and helobial endosperm to the monocotyledonous families. • Where the embryos grows slowly and seed contain immature undifferentiated embryo , the endosperm is cellular.
Types of Endosperm
1. Nuclear Endosperm: In this type of endosperm, the division of the primary endosperm nucleus and its further divisions are not followed by wall formation. • It is the most common type of endosperm found. • Here PEN divides repeatedly (mitotic division) without cytokinesis. It results in the formation of a large number of free nuclei in the cell. • A large central vacuole is formed and nuclei get arranged at the periphery. There are more nuclei at the chalazal and micropylar end, compared to the sides. • At this stage, cell wall formation takes place from the periphery towards the centre and multicellular endosperm is formed. Examples: maize, rice, wheat, cotton, sunflower, Limnanthes, Oxyspora
Figure: Stages in the development of nuclear type of endosperm. 1. Nuclear Endosperm:
In Lomatia, besides the main chalazal haustorium, numerous single- celled, fingershaped projections are present all over the endosperm. This increases the absorbing surface of the endosperm. 1. Nuclear Endosperm:
1. Nuclear Endosperm:  In Grevillea robusta, presence of vermiform appendage at the chalazal end of the endosperm is reported, in which, chalazal endosperm haustorium remains free- nuclear.
• In Crotalaria, the wall formation is confined to the upper region of the embryo sac, the chalazal region remains free- nuclear, and it often elongates and behaves like an haustorium. 1. Nuclear Endosperm:
In Coconut, the cell wall formation is incomplete resulting in the outer multicellular solid endosperm and inner multinucleated (having free nuclei) liquid endosperm (coconut milk) 1. Nuclear Endosperm:
Fig: Neuclear endosperm in Limnanthes 1. Nuclear Endosperm:
2. Cellular Endosperm:  It is not very common.  In this type of development, division of PEN (karyokinesis) is followed by cytokinesis and two cells are formed due to transverse division, giving rise to the chalazal and micropylar chamber. Further division is similar, which leads to the formation of the cellular endosperm.  Examples: Petunia, Balsam, Datura  The cellular endosperm is characterized by the absence of free nuclear stage.  The division of the primary endosperm nucleus and a few subsequent nuclear divisions are followed regularly by wall formation.  The occurrence of haustoria is a common feature of this type of endosperm;  It is more varied than that is the nuclear endosperm.  The haustoria may be micropylar or chalazal and occasionally, present in the same plant.
 A very aggressive chalazal haustorium is formed in Iodina rhombifolia.  The haustorium is actually formed before fertilization.  After fertilization, the division of the primary endosperm nucleus is followed by transverse partitioning of the central cell, resulting in the formation of a micropylar chamber and a chalazal chamber.  The endosperm proper is derived from the micropylar chamber alone. The chalazal chamber functions as an aggressive, uninucleate haustorium. Profuse branching at the free- end gives the haustorium a coralloid appearance.  In the Acanthaceae, the endosperm development is asymmetric and it shows characteristic micropylar and chalazal haustoria. 2. Cellular Endosperm:
2. Cellular Endosperm: Figure: Stages in the development of Cellular type of endosperm.
In Nemophilaboth micropylarand chalazalhaustoria are found. In Impatiens , micropylar haustorium is produced
3. Helobial Endosperm: • Development of helobial endospermis intermediate between nuclear and cellulartypes. • The first division is similar to cellular endosperm and results in a large micropylar cell and small chalazal cell. The chalazal cell mostly does not divide further and functions as a base cell. The micropylar cell divides further, similar to nuclear endosperm. So it is an intermediate type, a combination of both nuclear and cellular endosperm. • Examples: Eremurus • Helobial endosperm is more common in monocot.
TYPES OF ENDOSPERM
Function of Endosperm • Endosperm is important for the growth of an embryo and stores the food reserve • They supply nutrients and provide protection to the developing embryo • Endospermic tissues have shown to regulate gene expression and seed germination • Endosperm induces signals according to environmental conditions and regulates embryonic growth • The endosperm contains cytokinin, which regulates cellular differentiation • It may induce abortion of seeds from the genetically mismatched cross
ENDOSPERM HOSTORIA 1. MACADAMIA TERNIFOLIA : The lower free nuclear part forms many lobes or projections. Which invade the nutritive tissue at the chalazal end Of the ovule and functions as haustoria
Vermiform appendage. 2.GRAVILLEA ROBUSTA : In Gravillea robusta , the lower coenocytic Part of the endosperm is very aggressive & grows in the form of spiral, tubular worm like apendage. Hence it called Vermiform appendage. In this type the cells of the chalazal region of the ovule practically get dissolved due to the activity of the haustoria ( Aggressive haustoria). In later stages, the vermiform appendages gets partitioned into many large chambers. The cells formed in this way may be said to be secondary endosperm tissue.
Cucumis sativus • In cucumis ( cucurbitacae) a long chalazal haustorium is present. Soon after the fertilization, the lower part of the embrysac grows downward into a long tubular structure. • When the embryo is at the globular stage, the upper part of the endosperm becomes cellular and is designated as the endosperm proper. • The lower free nuclear part the endosperm further elongates and reaches deep down in the chalazal region. • The chalazal haustorium consists of dense cytoplasm and varied size of nuclei. • Sometimes the tip of the haustorium becomes swollen. • This haustorium transport the nutrients to the developing embryo.
Ruminate endosperm • It shows fringed outline or irregularly crinkled margin, bearing such type of endosperm is called Ruminate endosperm. • This is not a 4rth type of endosperm. Any one of the endosperm ( cellular, nuclear, helobial)may become ruminate endosperm. • This type of endosperm is found in 32 angiosperm familes. • In 1962 periasamy worked extensively on Ruminate endosperm. • Rumination of the endosperm is caused by the activity of the seed coat or by the endosperm itself.
• Rumination may be divided into 2 types 1. The inner layer of the seed coat are uneven and leave a number of gaps in the interior region. The surface of the endosperm growing rapidly and fills all this cavities and form the ruminate endosperm • Eg: Andrographis 2. In cocoloba, the rapid growth of the endosperm utilize the ephemeral nucleus and digests during the early stage of seed development. As a result of this the inner seed coat becomes uneven and affecting the surface of endosperm making it Ruminate.
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