What are Perisperm and Endosperm?
Perisperm is a botanical term used to describe a nutritive tissue which is a ruminant of the nucellus that remains persistent after the egg fertilization, surrounding the sac on the outer side of the embryo of a seed of some flowering plants called as angiosperms. It originates from the nucellus, centre most part of the ovule in the pouch of the embryo and acts as a food and nutrition storage for the seed. Perisperm is also called the albumen of the seed (Ramakrishna & Amritphale, 2005).
Perisperm is mostly seen in plants belonging to families like Piperaceae (Coffee and black pepper), Portulacaceae (Calandrinia, Waterleaf and Montia), Zingiberaceae (ginger), Amaranthaceae (Spinach and common beet), Chenopodiaceae (Beet root and Sugar beets), Cannaceae (Canna) and Caryophyllaceae (Carnation and Common Chicken weed). Perisperm lacks proteins and consists chiefly of starch and less commonly fat.
Endosperm is a scientific term used to describe a nutritive tissue which is formed inside the seed of many flowering plants following the cell fertilization. Endosperm envelopes the embryo of the seed and provide nutrition in the form of starch, and sometimes oil and proteins as well. Due to this nutritional aspect, endosperm possesses the potential to become a source of nutrition in the human diet. Endosperm originates from the endosperm nucleus.
Endosperm can be described as granular, bone like when horny, smooth and uninterrupted when continuous and possessing rough depressions when ruminated.
The endosperm is triploid in nature consisting of three sets of chromosomes (3n). It is a resultant of fusion of one sperm (1n) of the germinating pollen with the two polar nuclei present in the embryo pouch (2n). 90% of seed in corn and some cereals are composed of endosperm. In seeds of beans, the endosperm is absent as it gets used in the nourishment of seed embryo. Dicots are non-endospermic and Monocots are endospermic seeds like cereals including wheat and barley which are a source of dietary food in humans as well.
Endosperm seeds are seen in Euphorbiaceae family like onion and castor bean, coconut, corn, tomato, wheat and groundnut (Bewley & black, 1994).
Figure 1. Seed of Quinoa showing perisperm and endosperm (Prego et al, 1998, p.484).
Difference between Perisperm and Endosperm
Perisperm is basically diploid in nature i.e. it contains two sets of homologous chromosomes, one from the mother and one from the father. For e.g Piperaceae.
Around seventy percent of the flowering angiosperm plants consist of Polyploid endosperm cells. These cells are mostly triploid in nature but can sometimes vary from diploid 2n (Containing two sets of chromosomes) to even 15n (Containing from diploid 2n (Containing two sets of chromosomes) to even 15n (Containing 15 sets of chromosomes) for e.g Nuphar Polysepala (Olesen et al, 1998).
Perisperm is dry and a bit hard and mostly non-functional for a seed. It forms the protective covering for the embryo.
It can be in fluid form or soft (Rudall et al, 2009).
Persisperm originates from the nucellus enveloping the embryo before fertilization in the form of left over. Perisperm is diploid (2n) due to the separation of homologous chromosomes into two new nuclei.
Its origin is linked to double fertilization in which fusion of one sperm nucleus with the egg takes place to form the embryo and the second sperm nucleus fuses with the binucleate central cell to form the triploid endosperm (triple fusion nucleus). The cell which is formed after double fertilization forms Primary Endosperm Nucleus (PEN). Since there are two fertilizations involved, the endosperm results in a separate organism which is different from the embryo. (Lopes & Larkins, 1993).
4. Nutrition absorption
Perisperm originates from the nucellus and the endosperm absorbs the nutritive nucellus during its growth and development. So, it can be said that the endosperm gets its nutrition from persiperm.
The endosperm is located between the perisperm and the embryo and the nutrition in the endosperm is consumed by the embryo for its development (Mohana et al, 1988).
5. Maternal part
It is completely maternal in origin because it comes from the nucellus of the embryo sac of the seed.
Endosperm contains 2:3 maternal to paternal genome ratio (Shewry & Casey, 1999).
6. Found in
Perisperm is found only in some families of plants like Caryophyllaceae, Zingiberaceae, Nymphaea, Piperaceae etc. Among gymnosperms, it can be seen in Gneticae and Taxaceae (Friedman et al, 2012).
Endosperm is mostly found in all types of seeds (Werker, 1997).
In Perisperm, no cytoplasmic division of the cell (Cytokinesis) occurs e.g. Coffee.
Cytokinesis takes place e.g. corn.
Both Perisperm and Endosperm are nutritive tissues covering the embryo of the seeds. However, endosperm is found between the perisperm and the embryo sac which gives nutrition to the seed.
Perisperm is maternal in origin since it forms as a ruminant of the nucellus and is diploid (one mitotic division). Perisperm is found in many families of plants like Chenopodiaceae, Caryopyllaceae, Capparidaceae, Portulacaceae, Piperaceae and Zingiberaceae. Endosperm is mostly found in monocot seeds (having single cotyledon or embryonic leaf). The nutrition inside the endosperm of dicots is consumed by the monocots of the embryo before germination. Endosperm results due to double cell fertilization or double mitotic division, consisting of the primary endosperm nucleus. It is a resultant of fusion of one sperm nucleus with two polar nuclei and is called triple fusion nuclei. Therefore, the endosperm is triploid in nature most of the times. The major difference between perisperm and endosperm is in the development and growth of at the time of seed sprouting. Also, perisperm is the diploid nutritive reserve tissue and finds its origin from the nucellus whereas endosperm is the triploid nutritive reserve tissue that results from triple fusion nucleus.