Difference Between 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.

Integument

  • Outermost protective covering of the ovule
  • Angiosperms have two integuments while gymnosperms have one integument layer
  • It comprises living cells and is smooth and thin
  • Does not possess sclereids
  • Nucleus found at the micropyle opening to promote the entrance of pollens into ovule for syngamy
  • It is a pre fertilization structure, hence develops into testa once fertilization takes place

Testa

  • Exterior protective covering of the seed
  • Outer integuments emerges into testa and is brown in appearance
  • It is a post-fertilization structure
  • Two layers of testa – exotesta and endotesta, chiefly safeguarding the embryo that is developing
  • Also protects the seed while the seed disperses
  • It consists of sclereids as it is hard and thick
  • As it is impermeable to water it results in seed dormancy at times

Difference Between Integument and Testa

Following are some of the important differences between Integument and Testa.

Integument Testa
Outermost protective covering
Of ovule Of seed
Nature of cells
Living.

Thin and smooth

Non-living

Thick and hard

Fertilization stage
Pre-fertilization structure Post-fertilization structure
Number of layers
One or two Single layered
Sclereids
Absent Present
Seed dormancy
No role Impermeable to water, hence plays a key in seed dormancy
Origination
Arise from the chalazal ending of the ovule From outer integument of ovule once fertilization takes place
Function
To protect the ovule To protect the developing embryo
Permeability
Permeable to water Impermeable

Those were some differences between integument and testa. Watch this space at BYJU’S for more such differences for NEET.

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