Nucellus and tapetum are nutritive layers found in the ovary and anther, respectively. They both provide nutrients to the female and male gametophyte, however, they differ in their location and structure.
What is Nucellus?
The nucellus is a mass of cells, present centrally in the ovule of female gametophytes. It forms several layers of diploid cells just inside the integuments. The ovules contain the megaspore mother cells, which divide meiotically to produce megaspores.
The nucellus protects the developing embryo by providing nourishment. In angiosperms, the nucellus tends to degenerate while giving nutrients to the embryo, this makes a cavity for the embryo and endosperm to grow.
The nucellus often differs in its shape and size, which makes it characteristic of plant species.
What is Tapetum?
The tapetum is a nutritive layer of cells, present in the anther. The cells of the tapetum are polynucleate and big in size. The layer is located between the sporogenous layer and the anther wall. The chief function of the tapetum is to provide nourishment and regulatory molecules to the developing pollen grains.
Other functions of the tapetum include the synthesis of sporopollenin, the synthesis of callase enzyme for separation of the microspore tetrads, and the synthesis of pollenkitt and tryphine that acts as a binding material for the pollen grains.
The tapetum cells are of two types, amoeboid and glandular. The glandular tapetum remains intact around the anther locule, while the amoeboid tapetal cell walls disintegrate and forms a multinucleate plasmodium around the pollen sac.
Refer: Functions of Tapetum
Let us find out the differences between nucellus and tapetum now.
| The nucellus is a central mass of cells present in the ovules. | The tapetum is a layer of tissues present inside the anther walls. |
| The nucellus provides nourishment to the developing embryo and endosperm. |
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| It is found in female gametophytes. | It is found in male gametophytes. |
| It surrounds the embryo sac. | It surrounds the pollen mother cells or the microspores. |
| It is enclosed within the integuments. | It is enclosed within the anther walls. |
| It is always diploid in nature. | It is diploid in nature, but some cells may become multinucleate due to abnormal mitosis. |
Explore BYJU’S Biology for more interesting topics.
Also Read:
- The nucellus is made up of which type of cells?
- How Many Chromosomes Are Present In Nucellus?
- Explain the role of the tapetum in the formation of pollen grain walls.
Frequently Asked Questions
What is the difference between nucellus and endosperm?
The nucellus is a diploid tissue surrounding and protecting the embryo sac, whereas the endosperm is a triploid tissue that provides nourishment to the embryo.
What are the two types of tapetum?
The two types of tapetum are plasmodial and secretory.
What is the function of the tapetum?
The main function of the tapetum is to provide nutrients and regulatory molecules to the developing pollen grains.
Is sporopollenin secreted by tapetum?
The precursor for the formation of sporopollenin is secreted by the tapetum and deposited inside the anther locules.
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