Moss Reproduction

How they Reproduce Like all bryophytes mosses, have two forms of reproduction, Asexual or vegetative reproduction and sexual reproduction.

Sexual Reproduction At regular intervals depending on species and weather condition, mosses produce small sexual structures known as archegonium (female structure that produces egg cells), or antheridium (male structure that produces sperm cells). These can occur on different parts of the same plant but more often on different plants. The male plant sometimes has a visible rosette at the shoot tip, which contain a mass of antheridia among protective hairs or surrounded by modified leaves. In many moss plants a microscope is needed to see the antheridia or archegonia. When the antheridia are ripe the antherozoids are released, these antherozoids or sperm cells then swim by means of two threadlike tails and are attracted chemically to the archegonium, where fertilisation occurs to form a zygote. The formation of the zygote begins the second phase of the moss life cycle where the zygote develops into a sporophyte (spore-plant). The sporophyte begins to grow by cell division out of the top of the archegonium on the female gametophyte plant. At which point it's a parasite on the gametophyte plant, although it may produce some of its own food by photosynthesis in the early stages of growth . The sporophyte consists of three structures, a foot which anchors it to the gametophyte and helps to transfer water and nutrients from the gametophyte, a long erect stalk called a seta, and a pod-like capsule at the end where spores are produced. A capsule may contain from four, to more than a million, spores, depending on the species. In most mosses, the mouth of the capsule is covered by a lid-like operculum, which falls off when the spores are mature. A membranous hood, the calyptra, which is also discarded at maturity, further protects the operculum. A tiny tooth-like structure around the mouth of the capsule, which consists of one or two rows of teeth, controls the release of the spores. These structures called the peristome remain closed during wet conditions and preventing the release of the spore. In dry conditions, they open to allowing the discharging of the spores and improve their chances of the spore being dispersed some distance. If spore falls onto a damp area of ground, it may germinate into a branching, threadlike filamentous protonema. Buds from the protonema then grow into leafy male or female gametophytes, completing the life cycle.

Antheridia surrounded by modified leaves Antheridia surrounded by modified leaves Mature Moss Capsules Moss Capsules

Asexual Reproduction As mentioned above mosses can also reproduce asexually or other words vegetatively. They are able to do this by a number of different methods, much the same as Liverworts. One method occurs when the stem of a large clump of moss dies back, resulting the clump becoming individual plants. Another method occurs when bits of the stem or even a single leaf from the moss plant are accidentally broken off these bits can then regenerate to form a new plant. Some mosses produce specialised structures called brood bodies, which can take on many different forms depending on the species, and are often used to indicate the species of the moss plant.

Brood Body Campylopus introflexus

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