Question

Double fertilization is reported in plants of both Castor and Groundnut. However, the mature seeds of Groundnut are non-albuminous and Castor are albuminous. Explain the post-fertilization events that are responsible for it.

Answer 1

Double fertilization is the most distinguishing feature of flowering plants. In this process, one male gamete fertilizes the egg resulting in the formation of the zygote and the other male gamete combines with the two polar nuclei present in the ovary to form the endosperm, which has the primary function of nourishing the developing embryo.

Complete step by step answer: The endosperm formation starts when the primary endosperm nucleus (PEN), which is formed after fertilization divides by mitosis without cytokinesis. Thus, the endosperm formed is known as free nuclear endosperm, since there is no cell division followed by the nuclear division. This process is common in both albuminous and non-albuminous seeded plants.
The post-fertilization events that lead to the formation of different albuminous and non-albuminous seeds are:
In seeds such as Groundnuts, following this process, cell wall formation takes place and the endosperm gets converted into the cellular type, here, the endosperm formed gets completely used by the developing embryo before the seeds get completely matured. The seeds following this type of maturation are known as non-albuminous or non-endospermic seeds. Whereas, in Castor seeds, some portion of the formed endosperm remains, and the remaining portion is used up during the process of germination as it functions as an energy source to the germinating seedling. Such kinds of seeds are known as an albuminous or endospermic type of seeds.

Note: Embryo development after germination involves the fertilized ovule getting converted into seeds and the outer ovary getting converted into fruits. The different stages in embryonic development are:
i. Development of a globular proembryo and the suspensor.
ii. Embryo attains a heart shape with the cotyledons.
iii. Embryo starts to grow.
iv. Seed grows and gets filled with the embryo.