Dithecous Anther – Structure, Formation, and Theca

The dithecous anther is a bilobed structure found in flowering plants’ stamens. The dithecous anther consists of four microsporangia, two in each lobe. Upon maturation, the anther undergoes dehiscence, releasing pollen for pollination and fertilization. Dithecous anthers examples include solanum and mustard.

The dithecous anther plays a crucial role in the sexual reproduction and genetic diversity of angiosperms. In this article, we will learn about the structure, function, and formation of the dithecous anther in detail.

What is Dithecous Anther?

The name “dithecous” is derived from the Greek words “di” (two) and “theca” (pollen sac). Each theca contains microscopic structures known as pollen sacs or microsporangia. Theca formation in a dithecous anther occurs when the flower’s reproductive components grow. The anther starts to form when specific cells emerge in the early stages of flower development.

In a flowering plant, the anther is commonly divided into two sections, which are known as lobes. These lobes are commonly referred to as bilobed anthers. Each lobe of the anther comprises two chambers known as thecae. These compartments are where pollen grains are formed. Dithecous anther lobes are those that have two compartments each. Examples are angiosperms and crotalaria, solanum, and mustard.

Dithecous Anther Diagram

The labelled diagram of dithecous anther is given below:

Structure of Dithecous Anther

The structure of the Dithecous anther is explained as follows:

• Bilobed Structure: The anther is typically bilobed, meaning it consists of two lobes or sacs.
• Connective Tissue: A connective tissue called the connective holds the two lobes of the anther together.
• Locules: Each lobe of the anther contains a pair of locules (pollen sacs), where pollen grains are produced and mature.
• Microsporangia: Microsporangia are the specific structures within the locules where microspore mother cells undergo meiosis to produce microspores.
• Pollen Development: Microspores mature into pollen grains within the microsporangia, undergoing a process that involves the formation of a protective coat.
• Dehiscence: Dithecous anthers typically undergo dehiscence, where the lobes split open to release mature pollen for pollination.
• Filament Attachment: The anther is attached to the filament, which is part of the stamen, the male reproductive organ of the flower.
• Pollen Release: Upon maturation, the anther releases pollen into the surrounding environment, facilitating the transfer of male gametes for fertilization.

A Transverse Cross-Section of Dithecous Anther

A transverse cut of a dithecous anther reveals two microsporangia in each lobe, totaling four microsporangia. Pollen grains can be found in microsporangia, also known as pollen sacs. The anther resembles a plant’s male reproductive organ. It is divided into two portions, with four divisions inside where pollen is produced. These parts are known as microsporangia. Each microsporangium contains microscopic cells that produce male gametes, which resemble plant sperm. The anther has four layers around these pollen-producing sections:

1. Epidermis: It is the outermost layer, similar to the skin of the anther.
2. Endothecium: This layer lies just beneath the epidermis.
3. Middle layer: It is composed of 2-3 cell layers and often degrades as the anther grows.
4. Tapetum: This is the inner most layer that surrounds the pollen-producing cells and helps them expand.

Formation of Theca in Dithecous Anther

As the flower develops, certain cells transform into new sections, such as anthers. Special cells generate small structures known as microspores (microsporogenesis) within each region of the anther. This occurs through a process known as meiosis, in which each unique cell divides into four smaller ones. These microscopic cells develop into pollen grains. Each pollen grain contains small components that aid in the formation of sperm cells. As the anther expands, specific cells within it transform into distinctive shapes known as thecae. In anthers with two thecae, each component has its own sac for pollen grain growth.

The pollen component of a flower, known as the anther, is normally divided into two chamber-like pieces. Each segment contains two smaller pieces known as pollen sacs. These sacs are where the pollen grains develop. If the pollen sacs are not close together, the formation of chambers is disrupted, resulting in the absence of pollen sacs and chambers. Sometimes there is a gap down the middle that separates the two portions of the anther.

Functions of a Dithecous Anther

The anther’s major function is to produce pollen, which is similar to the plant’s sperm. The functions of the Dithecous Anther is as follows:

• The dithecal anther produces pollen through the development and maturation of microspores within the microsporangia.
• Within the pollen grains produced by the anther, male gametes (sperm cells) are formed, which are necessary for fertilization.
• The anther facilitates pollination by releasing mature pollen grains into the environment, promoting their transfer to the female reproductive organs, such as the stigma.
• Through the production and release of pollen, the dithecal anther contributes to genetic variation by allowing for the exchange of genetic material between different plants.
• The anther’s role in pollen production and dispersal is crucial for the successful reproduction of flowering plants, ensuring the continuity of their species.

Conclusion: Dithecous Anther – Formation of a Theca

The dithecous anther, which has two chambers and two pollen sacs in each, is essential for flowering plant reproduction. The pollen sacs generated within the anther are where pollen grains develop. These grains are extremely vital for plants to produce seeds via pollination and fertilisation. If something goes wrong with the formation of the theca, the pollen sacs may not grow properly, making it difficult for the plant to reproduce. Knowing about dithecous anthers allows us to better understand how flowering plants produce seeds.

FAQs on Dithecous Anther – Formation of a Theca

What is the Purpose of Theca?

To create a structural scaffold, androgens must be produced by thecal cells.

How Many Thecae are Present in a Bilobed Anther?

Bilobed anthers are those that have two lobes each. Typically, an anther contains two theca structures. Each theca generates two microsporangias. The dithecous anther produces four microsporangia.

What Distinguishes an Anther’s Lobe From its Theca?

The flat extension from the anther is known as lobe. The normal anther is a bilobed structure. An anther contains two theca. Additionally, the theca serves as a cavity or chamber for the lobes.

Does a Dithecous Anther Consist of Two Theca in Each Lobe?

Yes, a dithecous anther has two thecae in each lobe. Each theca has two pollen sacs or microsporangia. These microsporangia produce microspores that help develop pollen grains

How Many Microsporangia are Present in Dithecous Anther?

A dithecous anther consists of four microsporangia two in each lobe.

What is a Tetrasporangiate Anther?

A tetrasporangiate anther is an anther with four pollen sacs or microsporangia.

What is the Difference between a Lobe and Theca of an Anther?

In the anatomy of an anther, a lobe refers to one of the sections that make up the structure, while theca specifically denotes the wall of each pollen sac within the anther.

How Many Pollen Sacs are Present in Dithecous?

A dithecous anther has two pollen sacs, or microsporangia, in each of its two lobes. The cavity of the anther lobe is called a theca, and each theca has two pollen sacs.

What is Dithecous and Monothecous Anthers?

Dithecous anthers have two lobes with two pollen sacs each, while monothecous anthers have a single lobe with one pollen sac.

What is Theca in Anther?

The theca in anthers refers to the individual pollen sacs within the lobes, where pollen grains are produced and released during plant reproduction.