Biod Exp 5

EXPERIMENT 5: BRYOPHYTES AND SEEDLESS VASCULAR PLANTS: FERN ALLIES AND FERN Bryophytes (Seedless Non Vascular Plant) Characteristics: 1) Lack of lignified vascular tissue. 2) Have no flower and seed; reproduce via spores. 3) Require moist condition for at least part of their life cycle. 4) Generally divided into three groups: (i) Bryophyta (Mosses) (ii) Hepatophyta (Liverworts) (iii) Anthocerotophyta (Hornworts) (i) Mosses Mosses reproduce asexually and sexually. Asexual reproduction is achieved by producing diploid sporophyte. The sporophyte is an elongated structure elevated above the gametophyte. When it becomes sexually mature, the sporangium releases the spores that germinate into filamentous structures, called protonema, which will develop into gametophyte. The male sex organ is known as antheridium (plural: antheridia) whilst the female sex organ is called archegonium (plural: archegonia). After fertilization, the sporophyte will grow out of the archegonium.

Figure 1: The general life cycle of a moss.

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(ii) Liverworts A thallus in liverwort has special pores that permanently open for gas exchange. In some liverworts, a gemmae cup (cup-like structure) is the vegetative structure that produces gemmae (plural: gemma). This gemmae cup is growing on the upper surface of a thallus. When water hits the gemmae cup, the gemma will splash out and each of them is capable of growing into a new thallus. Sexual reproduction of liverwort is achieved by producing sperms and egg cells. In Marchantia, for example, the archegonia and the antheridia are elevated above their respective thallus structures on stalks called archegoniophores and antheridiophores. The liverwort sporophyte is a simple club-shaped sporangium that embedded in the archegonium. At maturity, the sporangium splits open to release spores. The release of spores is assisted by special hygroscopic hairs, called elaters.

Figure 2: The structure of a thallus.

Figure 3: The typical life cycle of a liverwort.

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(iii) Hornworts Hornworts are less common than liverworts or mosses. The sporophyte is ‘hornshaped’ and grows from a basal meristem, producing spores clustered around a central stalk. The spores will be released when the tip of the sporophyte split. Figure 4: The typical life cycle of a hornwort.

Seedless Vascular Plants: Fern Allies and Fern Characteristics: 1) Consist of lignified vascular tissue called phloem and xylem. 2) Reproduced via spores 3) Can be divided into four phyla: (i) Psilophyta (ii) Lycophyta (iii) Sphenophyta (iv) Pteridophyta (i) Psilophyta It consists of two genera: Psilotum and Tmesipteris. Psilotum, the whisk fern, is the simplest vascular plant with no leaves and root. It has only a photosynthetic stem. Tmesipteris has similar reproductive structures and life history to that of Psilotum, but it has broad leaf-like extensions of its stem, each with a single vascular bundle. (ii) Lycophyta It is commonly called club mosses, spike mosses, quillworts or ground pines. The genera Lycopodium and Selaginella are fairly common. For Lycopodium, sporangia may be spread all over the plant or they may be clustered in a cone-like structure called strobilus. The overall structure of sporangia on the axils of leaves is called sporophyll. Selaginella is different from Lycopodium because Selaginella is heterosporous, that is, it contains micro- and mega-sporophylls. (iii) Sphenophyta It is represented by the genus Equisetum, the horsetails or scouring rushes. It consists essentially of stem and the stem has very well defined nodes and internodes. Because its cell wall contains silica, it becomes natural scouring pad for cook ware. (iv) Pteridophyta 3

Ferns belong to the division of Pteridophyta. They do not flower but they can sexually reproduce by spores. Mature ferns produce spores on the underside of the leaves. When the spores germinate, they will grow into small heart-shaped plants known as prothalli (singular: prothallus). Male and female cells are produced on the prothallus. Figure 5: The general life cycle of a fern.

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