Pollen Sacs: Structure and Production

Pollen sac is the structure of a plant where pollen is produced. In angiosperms, each anther typically has four pollen sacs, which house the microspore mother cells. The microsporophylls that make up the male cone in gymnosperms bear varying quantities of pollen sacs. 

• Seed plants produce pollen due to the structural system in which pollen is produced. 
• Every anther of angiosperms has four pollen sacs that house the maternal cells for the microspores. 
• Depending on the species, gymnosperms generate varying numbers of pollen sacs on the microsporophylls that make up the male cone. 
• The pollen has two layers of distinct components in its outer layer as well as a cytoplasm that contains a tube cell.

Key Terms: Pollen Sac, Pollen Grain, Flowers, Tapetum, Epidermis, Endothecium Layer.

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Pollen Sacs

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A pollen sac is a floral structure that is either a component of the androecium or the male reproductive element of the flower. 

• Pollen grains develop in this sac. 
• The majority of blooming plants have two lobbed anthers. 
• The normal stamen is made up of the filament and the anther. 
• The connective connects the lobes of the anthers. 
• The male gametophyte that develops into male gametes is the pollen grain. 
• There are two microsporangia inside the theca of the anthers. 
• Microsporangia is the location where pollen grains are generated. 
• The various plants' anthers may be monothecal or monothecal. 
• Different techniques are used to distribute pollen from the pollen sac.

Read More: Fertilization in Plants

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Structure of Pollen Sacs

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The terminal bilobed structures are called anthers. 

• Two microsporangia are located in each lobe of each of the four tetragonal-shaped anthers that make up each anther. 
• Consequently, a developed anther is referred to as tetrasporangiate. 
• Plants' microsporangia aid in the development of pollen sacs, which, when they mature, become packed with pollen grains. 
• The primordial sporogenous cells, which are a homogeneous mass of meristematic cells that surround the anther wall, are part of the micro-sporangium, which has a spherical appearance. 
• The primary sporogenous tissues give rise to diploid microspore mother cells. 
• These pollens may produce sperm cells and are referred to as the microgametophyte of the angiosperms. 
• This pollen particle touches the appropriate stigma, where it develops into the pollen tube. 
• With the aid of this tube, the male gametes can reach the female gametophyte.

Read More: Sexual Reproduction in Flowering Plants

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Layers of Pollen Sac

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The layers of the pollen sac are–

• The outermost layer of an opposing wall is typically single-layered and serves as protection from the hostile environment outside. 
• Exothelium, a fibrous thickening known as the epidermis, can be seen in a few plant species. 
• Due to its hygroscopic nature, the endothecium of the anther wall is made up of alpha-cellulose fibrous bands that develop from the inner tangential wall layer and aid in the dehiscence of the anther. 
• The hydrophytes don't have these fibrous bands. 
• The central layer of the anther is typically thin and has one to three layers in most cases. 
• Upon maturation, this pollen wall layer's middle layer typically degenerates. 
• The sporogenous tissue is encircled by the tapetum, which is the innermost layer of the anther wall. 
• This cell assists in supplying food to the growing pollen grains. 
• This cell has a lot of cytoplasm and several nuclei.

Read More: Transpiration in Plants

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What do Pollen Sacs Produce?

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The pollen sacs basically produce pollen grains in the following process–

• The anther normally has four pollen sacs, each of which is primarily responsible for producing pollen grains. 
• Each pollen grain, which consists of a single cell, contains two male gametes. 
• When an anther reaches maturity, it splits open and spews pollen.

Read More: Autotrophic Nutrition

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Things to Remember

• A seed plant produces pollen sacs, which are a collection of microspores that, when collected, are only visible as a single microscopic particle. 
• Every pollen in seed-bearing plants is a tiny body with a range of forms and structures that grow in the male structures and are transmitted to the female structures by a number of methods during fertilization. 
• In angiosperms that produce flowers, the anthers of the stamens are what produce pollen. 
• In the microsporophylls of the microstrobili, which are located in the microsporophylls of the male pollen cones, gymnosperms manufacture it. 
• Depending on its size, pollen may contain one or more seeds and one or more reproductive cells. 
• There are no male gametes within the pollen grain.
• Flowers' capacity to transfer pollen tubes to their embryo sacs is essential to their ability to effectively reproduce sexually.

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