The key difference between integument and testa is that the integument is the outermost covering of an ovule, while the testa is the outermost covering of a seed.
Sexual reproduction takes place between two types of gametes: male and female gametes. The ovule is the female gamete while the pollen carries male gametes. Male and female gametes unite and produce a diploid zygote. The ovary is the structure that carries an ovule. Integuments are the protective coverings of the ovule. After fertilization, the ovule develops into a seed. Whereas, the outer integument develops into the seed coat known as a testa.
CONTENTS
1. Overview and Key Difference
2. What is Integument
3. What is Testa
4. Similarities Between Integument and Testa
5. Side by Side Comparison – Integument vs Testa in Tabular Form
6. Summary
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.
Figure 01: Integument
Furthermore, integuments do not enclose the nucellus completely. Nucellus remains open at the micropyle to facilitate entering of pollens inside the ovule for syngamy. Integuments originate from the chalazal end of the ovule. It is actually a pre-fertilization structure. Thus, integument develops into testa or seed coat after fertilization and maturation.
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.
Figure 02: Testa
Moreover, the testa protects the seed during seed dispersal. Therefore, it is a thick and hard covering consisting of dead cells such as sclereids. Moreover, it is impermeable to water. Sometimes this property of testa leads for the seed dormancy.
What are the Similarities Between Integument and Testa?
- Integument and testa can be seen in flowering plants.
- Both structures are related to the sexual reproduction of plants.
- Moreover, integuments develop into the seed coat when the ovule matures after fertilization.
What is the Difference Between Integument and Testa?
Integument and testa are two outermost coverings. Integument surrounds the ovule while testa surrounds the seed. So, this is the key difference between integument and testa. Moreover, the integument is a smooth and thin layer composed of living cells. In contrast, testa is a thick and hard layer composed mainly of dead cells. Furthermore, integument protects the ovule while testa protects the seed. Therefore, this is also a significant difference between integument and testa. In addition to these, the integument is a pre-fertilization structure, while testa is a post-fertilization structure.
Summary – Integument vs Testa
The integument is the outermost covering of the ovule. Therefore, it protects the ovule. It is a thin layer composed of living cells. Testa, on the other hand, is the protective outer covering of a seed. It is a thick and hard covering composed of dead cells, mainly sclereids. After fertilization, outer integument develops into testa. Testa protects the seed. It also plays a big role in seed dormancy. So, this is the summary of the difference between integument and testa.
Reference:
1.“Seed.” Wikipedia, Wikimedia Foundation, 8 Oct. 2019, Available here.
2. “Ovule.” Wikipedia, Wikimedia Foundation, 1 Aug. 2019, Available here.
Image Courtesy:
1. “Ovule-Gymno-Angio-en” By derivative work: Qef (talk)Ovule-Gymno-Angio-fr.svg: Original uploader was Tameeria at en.wikipedia. Translation and vectorisation by Cehagenmerak. – Ovule-Gymno-Angio-fr.svg (Public Domain) via Commons Wikimedia
2. “Coconut layers” By Kerina yin – Own work (CC BY-SA 3.0) via Commons Wikimedia