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  Seedless plants and Spermatophytes, Biology tutorial

Introduction to Seedless plants and Spermatophytes:

The plant kingdom includes the Bryophytes, Pteridophytes, the Gymnosperms and the Angiosperms. They all possess chlorophyll and are autotrophic. They are generally immobile

Division Bryophyta:

Introduction:

They are first division in plant kingdom. Bryophytes were the earliest land plants and are the transitional group between terrestrial and aquatic plants. Not like algae, they are multicellular and more complex.

Diagnostic characteristics:

i) They are ancient plants that can only survive in wet damp or shady places.

ii) They don't possess stems, true roots, or leaves.

iii) They don't possess vascular tissues of xylem and phloem.

iv) Their sizes are small.

v) The gametophyte generation is leading stage of life cycle.

vi) The sporophyte is joined to and dependent on gametophyte for nutrition.

vii) The spores are made by sporohyte in spore capsule on end of the slender stalk above gametophte

Categorization:

The Division Bryophyta is separated into 3 classes, they are

i) Hepaticae or liverworts e.g Riccia, Marchantia

ii) Anthocerotae or Horned liverworts e.g Anthoceros

iii) Musci or Mosses e.g Spagnum, Funaria Polytrichum

Adaptive Features:

i) They have pores on their leaves which allow the entry of atmospheric oxygen.

ii) Air-dispersed asexual spores.

iii) The embryo is developed within the female sex organ; (this is a feature of all terrestrial plants).

iv) They cannot withstand desiccation; this is because they do not have a cuticle.

v) However, the Bryophytes are still limited to moist areas as they still require aquatic medium for the male gametes to travel to the female egg before fertilization can occur.

Division Pteridophyta:

Introduction:

The term Pteridophyte refers to non-seed vascular plants, i.e. plants with xylem and phloem whose dispersal relies on spores not seeds. The sporophyte is the dominant phase of life cycle of Pteridophytes.

Diagnostic Characteristics:

i) They are specialized plants

ii) The sporophyte is the dominant and conspicuous generation

iii) The gametophyte generation of Pteridophytes is small and found in wet places

iv) The sporophyte is differentiated into true roots, stems and leaves

v) They have vascular system composed of xylem and phloem

vi) The epidermis of pteridopytes is covered by cuticle and also possesses stomata.

vii) The sporophyte produces spores which may be homosporous or heterosporous

Classification of Pteridophytes:

There are 4 classes of Pteridophytes which are

i) Psilotopsida example Psilotum and Tmesipteris

ii) Lycopsida example Lycopodium,Selaginella

iii) Sphenopsida example Horsetails,Equisetum

iv) Pteropsida or Filicinae example Fern,Azolla. Adiantum

Adaptive features:

i) They possess true roots, leaves and stems

ii) They possess a vascular system composed of xylem and phloem.

iii) Their epidermis is covered by cuticle

iv) Their epidermis has stomata that assists to control water loss

The Spermatophytes:

Introduction:

This plant kingdom comprises Bryophytes, Pteridophytes, Gymnosperms and Angiosperms. Gymnosperms and angiosperms make spermatophytes. They all have chlorophyll and are autotrophic. They are normally immobile

Division Gymnospermae:

Introduction:

They are plants that produce naked seeds. Most of the members of this division are extinct no living representatives.

Diagnostic features:

i) The seeds are naked i.e. not enclosed

ii) The seeds are borne on a cone Leaves - needles bundle of 3 is called a fascicle.

iii) Archegonia is present with eggs.

iv) Germinations are short

v) Single fertilization

Examples: Cycas, Pinus, Gnetum.

Categorization:

A) CYCADOPSIDA e.g Cycas

B) CONIFEROPSIDA e.g Pinus

C) GNETOPSIDA e.g Gnetum

Division Angiospermae:

These are plants which bear flowers and make seeds. They are also known as flowering plants . Many plants around us belong to division. Orange, mango, papaya flamboyant, banana, baobab, grasses, etc. all belong to the division. They have been able to effectively adapt to life on land. Plant standing is generally sporophyte generation.

Diagnostic Features:

i) Seeds are covered

ii) Seeds are enclosed by flower or fruit

iii) No archegonium present

iv) Germination is long

v) Double fertilization (3N) structure

Morphology:

Plant body is separated into root system and shoots or stems system, connected by vascular tissue which is continuous throughout plant. Root system of the dicot comprises of taproot and many lateral roots. Shoots comprises of stems, leaves, and flowers. Blade, expanded portion of the leaf, is joined to the stem by the petiole.

Categorization:

There are 2 classes of angiosperms which are

i) The Monocotyledonae and

ii) Dicotyledona

Adaptive Features:

i) Possession of the waxy cuticle,

ii) They possess surface pores (stomata) which allow gas exchange

iii) Possession of the effective vascular system (xylem and phloem) for transport of water and mineral salts and translocation of produced food

iv) Retention of embryonic sporophyte within female gametophyte

v) Many of the flowers are developed to attract pollinators, like nectar, colors, and fragrances

vi) Their fruits are frequently developed to help in dispersal of their seeds.

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