Integument and Testa – Class 12 | Chapter – 2 | Biology Short Notes Series PDF

Integument and Testa: Integument is the exterior or the outermost covering of an ovule. Testa, on the other hand, is the exterior or outermost seed covering. In sexual reproduction, both the gametes fuse, forming a zygote (diploid). Ovary carries the ovule, which in turn is protected by the covering known as integuments. Seeds are developed from the ovule once fertilization occurs while integument develops into the seed coat referred to as testa.

What is Integument?

The integument is the outer covering of the ovule. It is a protective layer. Gymnosperms have a single integument while there are two integuments surrounding the ovule in angiosperms. Structurally, the integument is thin and smooth. It consists of living cells. Hence, it does not contain sclereids, unlike testa.

What is Testa?

Testa is the outermost protective covering of the seed. Thus, it is one of the two seed coats which is brownish in colour. The outer integument gives rise to testa. Hence, it is a post-fertilization structure. Structurally, there are two layers of the testa as endotesta and exotesta. Its main function is to protect the developing embryo from mechanical damages and dehydration.

Differentiate between Integument and Testa

Integument Testa
  • An integument is an outer covering of the ovule.
  • Testa is an outer covering of the seed.
  • It is a pre-fertilization product.
  • It is a post-fertilization product.
  • The cells of the integument are thin and soft.
  • The cells of the testa are thick and hard.
  • They do not contain sclereids.
  • They contain sclereids.
  • The cells of integument are living.
  • The cells of the testa are dead.
  • It may consist of one or two layers of cells.
  • It may consist of one layer of cells.
  • It is developed from the chalazal end of the ovule.
  • It is developed from the integuments of the ovule.
  • Through integument, pollens enter the ovule.
  • It is formed after the fusion of pollen and egg cells.
  • They form inner layer tegmen and outer layer testa.
  • The testa fused with the fruit wall called the pericarp.

 


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