Q. Remnants of nucellus are found in which of the following?
Solution:
Inside the ovary of the flowering plants, one or multiple ovules are present. The ovule is attached to the placenta of the ovary by a stalk known as the funicle. The portion where the funicle fuses with the ovule is known as hilum. Each ovule has one or two protective coverings known as the integuments. Integuments cover the ovule except at the point where the pollen tube enters the ovule. This point is known as the micropyle. Inside the integuments, there is a mass of cells known as the nucellus. Inside the nucellus, the embryo sac is present. Nucellus has abundant reserved food material necessary for the female gametophyte (embryo sac).
When the fertilization process has taken place in which the egg cell fuses with one sperm nucleus and the two polar nuclei fuse with another sperm nucleus, the seed development process initiates. In this, the embryo development takes place from the zygote, and the primary endosperm nucleus starts developing into endosperm through various developmental procedures. At this point, the nucellus begins to degenerate.
However, in some plants, the nucellus does not degenerate completely. This persistent nucellus is known as Perisperm. In other words, perisperm can be defined as a nutritive tissue that is derived from the nucellus and is present externally on the embryo sac (female gametophyte). It is highly nutritious and promotes growth and development. It is found in black pepper, sugar beet, castor, coffee, etc.
