Question

Do gymnosperms have endosperm?

Answer 1

Hint:
1. Endosperm is a tissue formed following the fertilization, within the seeds of most flowering
plants. It envelops the embryo and provides nutrients in the form of starch.
2. Gymnosperms are plants that have no flowers. Their seeds are naked and do not have double fertilization. Thus, the endosperm formed is not real.

Complete answer:
Gymnosperms and Angiosperms have different origins for their endosperm. Double fertilization occurs in Angiosperms where one sperm nucleus fertilizes (n) the egg (n) and forms the embryo (2n). While the other sperm nucleus (n) fuses with the two polar nuclei (n each= n+n) in a large central cell of the female gametophyte, resulting in a triploid cell (3n). This triploid cell will grow into a true endosperm.

Gymnosperms, on the other hand, do not have double fertilization. As a result, there is nothing as a true endosperm. Let us consider the life cycle of pine to understand better. Ovules are found in the ovulate cones and consist of a diploid cell called a megasporocyte within a megasporangium (2n), all of which is protected by an integument.

These three elements form the Ovule. Only one of the four haploid megaspores produced by the megasporocyte survives (n) after undergoing meiosis. This megaspore matures into a female gametophyte with two or more tree archegonia; each one will form an egg.

Microsporocytes (2n) are cells located within microsporangia in pollen cones. Meiosis occurs in these microsporocytes, resulting in haploid microspores (n). Each microspore becomes a pollen grain (n), which contains the male gametophyte. Two prothallial cells, the generative cell, and the tube cell make up the pollen grain.

The generative cell and the tube cell are responsible for reproduction, while the other two degenerates rapidly. The four-celled microgametophyte generative cell divides, producing two types of cells: a sterile cell and a spermatogenous cell. The spermatogenous cell divides to create two sperm nuclei before the pollen tube enters the megagametophyte.

The egg nucleus joins one sperm nucleus, while the other nucleus degenerates. In this process, the female gametophyte contained many cells, but only the eggs were used for fertilization. The food reserves are then this feminine gametophyte tissue (n) or in other words the primary endosperm.

Note: In angiosperms, the only way for the formation of the endosperm is through fertilization. But in Gymnosperms, the feminine gametophyte is formed even if there is no fertilization .
This indicates that in Gymnosperms, all the energy invested in the generation of the feminine gametophyte could be wasted if no fertilization occurs.