Gymnosperms : Summary

Summary

Plant Kingdom includes Algae, Bryophytes, Pteridophytes, Gymnosperms and Angiosperms The life cycle in plants fall under three types 1. Haplontic,2. Diplontic and 3.Haplodiplontic.

Algae are autotrophic, chlorophyll bearing organisms. The Plant body is not differentiated into root like, stem like or leaf like structures. A wide range of thallus organization is found in algae. They reproduce vegetatively through fragmentation, tuber and akinete formation. Zoospores , autospores and hypnospores are produced during asexual reproduction and Sexual reproduction occurs through isogamy, anisogamy and oogamy.

Oedogonium is a fresh water, filamentous, multicellular alga. The presence of cap cell is the prominent characteristic feature in addition reticulate chloroplast is present. Asexual reproduction takes place through Zoospores. The sexual reproduction is Oogamous.

Chara is a fresh water alga and is popularly called “Stone worts”. The plant body is multicellular, macroscopic and is differentiated into main axis and rhizoids. Sexual reproduction is Oogamous.

 Bryophytes are simplest land plants. They are called amphibians of plant kingdom or nonvascular cryptogams. The plant body is gametophyte. The sporophyte depends upon gametophyte. Conducting tissues like xylem and phloem is absent. Vegetative reproduction takes place through fragmentation, formation of adventitious bud and Gemmae. Sexual reproduction is Oogamous. Water is essential for fertilization.

Marchantia belongs to the class Hepaticopsida. The thallus is dorsiventral and is attached to the substratum by means of rhizoids. The internal structure of the thallus reveals the presence of photosynthetic region and a storage region. Vegetative reproduction takes place through fragmentation and formation of Gemmae. The sexual reproduction is Oogamous. Sporophyte bears spores. Alternation of generation is present.

Funaria belongs to the class Bryopsida. The gametophyte is differentiated into leaf-like, stem-like structures with rhizoids. Gemmae, Protonema and bulbils help in asexual reproduction. Sexual reproduction is Oogamous. Alternation of generation is present.

Pteridophytes are also called vascular cryptogams. The plant body is sporophyte and is long lived ,which is differentiated into root, stem and leaves. They may be homosporous or heterosporous.

The sporangia with spores are found in sporophylls. The sporophylls organise to form cones or strobilus. The spores germinates to produce haploid, multicellular heart shaped independent gametophyte called prothallus. Sexual reproduction is Oogamous. The life cycle shows Alternation of generation.

The term stele includes central cylinder of vascular tissues comprising xylem, phloem, pericycle, endodermis and pith . There are two major types of stele namely Protostele and Siphonostele.

Selaginella belongs to the class Lycopsida. The plant body is sporophyte. It is differentiated into stem, leaf, rhizophore and roots. Heterospory is found and two types of spores namely microspores and megaspores are produced in sporangia. The microsporangia and megasporania are borne on sporophylls. The sporophylls are organized to form cone. Sexual reproduction is oogamous. Alternation of generation is present.

Adiantum belongs to Pteropsida. The sporophyte is differentiated into root, rhizome and leaves. The spores are produced in sporangia and is covered by false indusium. The sexual reproduction is oogamous and sex organs (antheridum and archegonium) are produced on prothallus. Alternation of generation is present.

Gymnosperms are naked seed producing plants. The plant body is sporophyte and it is the dominant phase. Coralloid roots are found in Cycas. The roots of Pinus possess Mycorrhizal association .Two types of branches called Long shoot and dwarf shoot are present. Stem shows secondary growth. Spores are produced in cones. Pollen tube helps in fertilization.. The endosperm is haploid . Alternation of generation is present

Cycas belongs to Cycadopsida. The plant body is sporophyte and looks like a small palm tree. Apart from Taproot Coralloid roots are present. It is dioecious, Microsporophylls are organized into male cone. Ovules are borne on megasporophylls which are not organized into cone. Fertilization results in zygote and it develops into embryo. Alternation of generation is present.

Pinus belongs to Coniferopsida.. The plant body is sporophyte and is differentiated into root, stem and leaves. The main stem is branched. The branches are dimorphic with long and short branches. It is monoecious, heterosporous and produces two types of spores called microspores and megaspores. Alternation of generation is present.

Angiosperms are highly evolved plant group and their ovules remain enclosed in an ovary. A wide range of habit is present.. These include trees, shrubs, herbs, climbers, lianas. Double fertilization is present. The endosperm is triploid. They are classified into Dicotyledons and Monocotyledons.