Short notes on Sexual Reproduction

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Funaria is monoecious. Antheridium, the male sex organ and archegonium the female sex organ, borne on separate shoots of the same plant (monoecious).

The main shoot of the gametophyte bears a cluster of antheridia at the apex and acts as a male branch. The female branch develops later as a lateral shoot from the base of the male branch which grows vigorously and becomes longer than the main or male branch.

Antheridia

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Antheridia are produced in clusters and they are intermingled with a large number of sterile multi cellular hairs known as paraphyses.

The tips of paraphyses are swollen. Antheridia and paraphyses are surrounded by a number of bracts like leaves, which form a resette called the perichaetium at the apex of the antheridia shoot. A mature antheridium is a long stalked club shaped structure having a single layered jacket.

There occurs a dense central mass of numerous androcytes within the jacket (sperm mother cells). When the mature antheridium comes in contact with water, the apical cell bursts and the mass of androcytes are liberated steadily through the perforated opercular cells. On reaching the water surface, each androcyte is metamorphosed into a biflagellate anthcrozoid.

Archegonia

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Archegonia are formed in clusters at the apices of the lateral branches or female shoot. These are surrounded by a whorl of perichaetial leaves and are intermixed with a large number of hairs like paraphyses.

The mature archegonium is a flask shaped structure having a long stalk, a swollen Venter and a long neck. The stalk is multi cellular. The Venter is swollen, consists of two layered jacket and encloses a Venter canal cell and an egg.

The neck consists of six vertical rows of cells enclosing 6 or more neck canal cells. The Venter is composed of one ventral canal cell and an egg. The has a egg cell prominent nucleus known as egg – nucleus.

Fertilization

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In Funaria, the antheridia mature first and the archegonia later, to ensure cross fertilization. Fertilization is effected through the medium of rain water or dew drops collected at the apex of the plant.

The archegonium secretes mucilage and sugar which attract the antherozoids. The neck-canal cell and ventral canal cell disintegrate forming a clear passage for the entry of antherozoids. The antherozoids move to the Venter and only one of the anterozoids fuse with the egg, forming zygote or oospores.

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