What is the Difference Between Theca and Microsporangia

Theca and microsporangia are two related parts in the anther of the flowering plants. The anther is very important for flowering plants because it helps the flower to create pollen. Without them, the flower cannot produce pollen or cannot reproduce.

The key difference between theca and microsporangia is their structure and position. Theca is the cavity of the anther lobe in flowering plants while microsporangia are the pollen sacs in the cavity of the anther lobe in flowering plants.

CONTENTS

1. Overview and Key Difference
2. What is Theca  
3. What is Microsporangia
4. Similarities – Theca and Microsporangia
5. Theca vs Microsporangia in Tabular Form
6. Summary – Theca vs Microsporangia
7. FAQ – Theca and Microsporangia

What is Theca?

The anther in a typical flowering plant has two lobes. They are termed as bilobed anther. The cavity of the anther lobe is known as theca. The theca is also separated by a groove that runs longitudinally. Anther has two thecae. Each theca generally carries two pollen sacs or microsporangia. Some anthers may not have theca as well. This is because if the pollen sacs are not placed together, the formation of theca is disturbed.

Figure 01: Anther (1: Filament 2: Theca 3: Connective 4: Pollen Sac)

The outer cells of the theca form the epidermis, which is a single layer of cells that covers the flower. Below the epidermis, there are somatic cells that form the tapetum. The tapetum support the development of microspores into mature pollen grains.

What are Microsporangia?

Microsporangia are the pollen sacs in the anther of flowering plants. Each theca or cavities of the anther has two pollen sacs or microsporangia. A microsporangium produces microspores. When microspores are germinating, they give rise to male gametophytes. Microsporangia occur in all vascular plants, such as seed plants, spike mosses, and aquatic ferns.

Figure 02: Microsporangia

Microsporangia produce microsporocytes. Microsporocytes are the microspore mother cells. These microspore mother cells produce four microspores through the process of meiosis. Microspore mother cells are diploid, while microspores are haploid. Ultimately, these microspores become pollen grains.

Similarities Between Theca and Microsporangia

1. Theca and microsporangia are two parts in the anther of the flowering plants.
2. Both are related to each other.
3. They are found in vascular plants that have heterosporic life cycles.
4. Both help the reproduction of the flowering plants.

Difference Between Theca and Microsporangia

Definition

1. Theca is the cavity in the lobes of anther.
2. Microsporangia are sporangia that produce microspores, which give rise to male gametophytes when they germinate.

Reproduction and Genetic Diversity

1. Theca is not directly connected to reproduction and genetic diversity.
2. Microsporangia is directly connected and very important to the reproduction and genetic diversity of flowering plants.

Formation

1. As the anther expands, the specific cells within it transform into distinctive shapes known as thecae.
2. As the flower develops, certain cells transform into new sections called anthers; within that there are special cells that generate small structures known as microsporangia.

Function

1. Thecae carry microsporangia and form the epidermis of the flower that covers the flower.
2. Microsporangia produce microspores, which develop into pollen grains.

The following table summarizes the difference between theca and microsporangia.

Summary – Theca vs Microsporangia

The male reproductive part in the flowering plants is called the stamen, and it is broken into two parts: the filament and the anther. An anther is the part of the stamen where the male gametophytes are produced in a flower. Theca and microsporangia are two parts in the anther of flowering plants. Theca is the cavity in the lobes of anther that carries the microsporangia, while microsporangia are the specific structures within the locules or lobes of anther where microspore mother cells undergo meiosis to produce microspores. This is the summary of the difference between theca and microsporangia.

FAQ: Theca and Microsporangia

1. What is the structure of anther?

• The anther is a bilobed and dithecous structure. Theca is a cavity on the anther lobes. Each theca has microsporangia in each lobe. Thus, anther have four microsporangia in total.

2. Is a theca a pollen sac?

• Theca is a cavity in each of the anthers. Each theca generally carries two pollen sacs or microsporangia. The pollen sacs are elongated cavities in which pollen grains are produced.

3. Are pollen sacs male or female?

• Pollen grains are male gametophytes and carry male gametes. Hence, the content of the pollen sacs is male gametophytes. Therefore, pollen sacs are male parts of flowering plants.

4. What is the microsporangium of a plant?

• A microsporangium is a sporangium that produces microspores that give rise to male gametophytes when they germinate. Microsporangia occur in all vascular plants, such as seed plants, spike mosses, and the aquatic fern genus Azolla.

5. What is the ploidy of microspore?

• Microspore mother cells called microsporocytes undergo meiosis and form four microspores. These four microspores are called microspore tetrad. And each microspore is haploid, so the ploidy of microspore tetrad is haploid.

Reference:

1. “Understanding Dithecous Anther – Structure, Theca and FAQ.” Testbook.
2. “Microsporangia – An Overview.” ScienceDirect.

Image Courtesy:

1. “Anther-schematic” By Original: Ben Stefanowitsch Vector: TilmannR – Own work based on: Anther-schematic.png (CC BY-SA 2.5) via Commons Wikimedia
2. “Microsporangia of C. micronesica” By Chamorroplants671 – Own work (CC BY-SA 4.0) via Commons Wikimedia

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