Plant Kingdom Test - 1

Bryophytes shows two morphoiogically distinct heteromorphic generations, i.e., gametophytic and sporophytic generations. Gametophytic generations is the dominant phase of life cycle and in general the term 'plant body' is used to represent this phase. In bryophytes, sporophyte is parasitic(partially or wholly) on the gametophyte as it is organically attached and is nutritionally dependent upon the gametophyte.

In Marchantia, the plant body consists of a dorsrventrally flattened, prostrate and dichotomously branched thallus. The thalli are conspicuous, apex of each thallus is notched. Along the midriba represent characteristic, prominent goblet or cup-shaped structures, the gemma cups, with smooth, dentate or frilled margins. These cups enclose asexual reproductive bodies called gemma.

Fertilization of Funaria occurs in water. The antherozoids are released into water where they swim and reach archegonium. An antherozoid fuses with the egg to produce the zygote. Thus an external layer of water is essential for the swimming of male gametes to the archegonia.

In bryophytes, the zygote develops into a multicellular, undifferentiated structure called embryo. The embryo, within venter of archegonium, by further segmentation and differentiation finally develops into a full fledged sporophyte called sporogonium.

Bryophytes are known as 'amphibians of plane kingdom' because they are adapted to land as well as water habitats. In their vegetative structure, bryophytes, have become adapted to land. But they depend on water for sexual reproduction because the swimming habit is retained by their sperms.

The resemblances between algae and bryophytes are given below:
(i) Algae and bryophytes both are autotrophic.
(ii) Algal plant body is a thallus, like many bryophys (Hepaticeae and Anthocerotae).
(iii) In both, reserve food material is generally starch.
(iv) Both |ack vascular tissues.
(v) Water is essential for fertilization in algae as well as in bryophytes.

Sexually Marchantia is dioecious with sex organic borne on stalked upright receptacles or gametophoers. Gametophore of male thallus is called Antheridiophce having a stalk and a 8 lobed male receptacle. Gametophce of female thallus is called archegoniphore. Its receptacle has nine cylindrical processes or rays.

Sperm of mosses is biflagellated. i.e. it has two flages that aid in propulsion. Since sperm must swim to the archegonium fertilization cannot occur without water.

Bryophytes are divided into liverworts, hornwortsa are mosses. Liverworts may be thallose or foliose, but mosses are always leafy. Plant body in liverworts is dorsiventrala are rhizoids are unicellular. In mosses plant body has a rade symmetry, rhizoids are multicellular.

The sex organs in bryophytes (Riccia, Funari pteridophytes and gymnosperm (Cycas) are multicellds and jacketed. The jacket of sterile cell around the sperm as egg is an adaptation to a life on land. The male reproduction organs are antheridia and female reproductive organs are archegonia.

Mosses form a protective covering over the crumbling soil of cliffs and prevent the sushing rainwater from cutting deeply into the soil. These grow in dense mats so firmly enterwied around the soil particles that there can be tittle erosion, eve on a steep hill side.

The gametophytic plant body of liverworts is usually dosiventral, leaf-like and gives the appearance of liver. The common examples of liverworts are Riccia, Marchantia, Piccia, etc.

Riccia is a livewort (Hepaticae), which grows predominantly in wet terrestrial habitats and are free floating or submerged auatic.

The plant body of bryophytes is thalus-like and prostrate or erect, attached to the substratum by unicellular or multicellular rhizoids. They lack true roots, stem or leaves. However, may possess root-like, leaf-like or stem-like structures. The main plant body of the bryophyte is haploid.

Peat consists of deposits of vegetable matter which have accumulated in bogs and swamps and slowly decomposed, becoming somewhat carbonised and compacted. It is dark brown in colour. Peat is built by Sphagnum moss, for this reason, Sphagnum is called peat moss. Peat is used as fuel and manure.