Question

What is meant by perisperm?

Answer 1

The above term is associated with seed. The fertilized ovule is known as a seed. Seeds are produced in both types of plants- the Angiosperms (flowering plants) and the Gymnosperms (non-flowering plants). Essentially, a seed contains a miniature plant (embryo) that awaits germination and is sometimes nourished by the surrounding nutritive tissue and packed upon by the seed coat. The outer layer of the seed coat is known as testa and the inner layer is known as tegmen.

Complete answer:
Now, basically a seed is of three types:
Endospermic/Albuminous seeds: Seeds where the endosperm is persistent. E.g., Wheat, Maize, Barley, Sunflower, Coconut, Castor, etc.
Non-endospermic/Exalbuminous seeds: Seeds where the endosperm is totally consumed during development. E.g., Pea, Bean, Groundnut, etc.
Perispermic seeds: Seeds in which the remains of the nucellus are seen. The residual, persistent nucellus is known as perisperm. E.g., Black pepper, Beet, etc.

Note:
The nucellus is also a kind of nutritive tissue that nourishes the growing embryo which awaits germination under favorable conditions. The nucellus is often consumed during the seed development process. The nucellus also takes part in a phenomenon called Apomixis, where embryos are developed without fertilization from the diploid parts of the seeds (other than the egg). Examples include Citrus, Opuntia , Mango, etc. More correctly, this can be termed as Adventive Embryony or Sporophytic Budding.
Thus, both the endosperm and nucellus serve the common purpose of nourishing the embryo. The perisperm appears relatively dry in nature whereas the endosperm is often in fluid form or is soft.