Brpyophytes

introduction

 Bryophytes include one of the most important group of cryptogams. his group is intermediate in between 1hallophytes and Piendophytes. hese plants generally grow in moist, shady places. The species of bryophytes occur in diverse habitats. They are terrestrial, aquatic Species OT phagnum, Riela), epiphytic on tree barks (Mosses, Denaroceros) nd some are saprophytic (Bunbaumia minakate, B. apnyita, COptothalus mirabilis). There are about 980 genera and more than 24,000 Species of bryophytes found in world. All bryophytes requires water 1or ne process of fertilization, indicating incomplete adaptations for land habits and therefore, they are considered as "Plant amphibians" The main plant body represents the gametophytic phase and it 1s independent, green and branched. The sporophyte is totally dependent upon gametophvte. The premitive bryophytes are prostrate thalloid, while evolved Torms show erect plant body with main axis (stem) and lateral appendages (leaves). These plant lack true roots but rhizoids are seen for anchoing the plant. The scales are also found in thalloid forms. Bryophytes show absence of true conducting elements - xylem ad phloem. The bryophytes reproduce by vegetative and sexual methods. The vegetative reproduction takes place by decay-death of thallus tissue; by production of adventitious branches, by production of tubers and gemmae. The sexual reproduction is oogamous. The male sex organ is antheridium and the female sex organ, archegonium. The sex organs are multicellular and more complicated in nature. Water is essential for fertilization. The antherozoid nucleus fuses with egg nucleus during fertilization and produces diploid zygote (2n). Zygote is the first cell for sporophyte. Zygote immediately germinates and starts sporophyte development. The zygote divides transversely and produces embryo. Embryo develops into sporophyte without stem and leaves. The sporophyte in bryophytes consists of foot, seta and capsule. In Riccia, only capsule is present while in Anthoceros sporophyte shows capsule and foot, scta is absent. Introductlon

 The sporogenous cells of capsule undergo reduction division (meiosis) and form haploid spores. All spores are similar in size and shape, so the Byopnye are homosporous. The spores are non-motile and dispersed oyop ophy er favourable conditions, the spore germinates to produce by winor the gametophyte. In Funaria, germinating spore produces pew piThe buds present on protonema develops into new gametophytic protonema. Ihe buds p plant hytes exhibit regular and distinct alternation of generations, Bryophyt d sporophyte. The gametophyt is the main plant body. ga Smith (1955) divided division Bryophyta into three classes namely tiene, Anthocerotae and Musci. These names were latcr on modified roskauer (1957) following International Code of Botanical menclature (ICBN). The new suggested terms are Hepaticopsida, Anthocerotopsida and Bryopsida. The bryophytes has great economic importance in relation to evolutionary Significance. ANTHOCEROTPSIDA 3.1 General Characters The class Anthocerotac comprises about 6 genera and 300 species, widely distributed in the tropical and temperate regions of the world. They exhibit folloWing important characters: 

1. The gametophytic plant body is green, dorsiventrally flattened, Iobed thalloid structure.

 2. The gametophytic thallus gets attached to the substratum by means of numerous smooth walled rhizoids.

 3. The ventral scales and tuberculated rhizoids are absent.

 4. Internal structure reveals that there is no differentiation of photosynthetic and storage region in the thallus. The cells possess chloroplasts and pyrenoids. Ihere are no air chambers or air pores, but some species have i ar cavities with slit like opening on the ventral surface of the nallus. The slit like s ricture is known as slime pore. The sex organs are found embedded in the gametophytic tissue. nrEproductive structure is called antheridium. The antheridia develop n e dorsal surface of the thallus and hypodermal in region. he antheridia occur either singly or in groups within the antheridial chamber.

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