Write in details about the different divisions of plant kingdom.
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Explanation:
Kingdom Plantae
Genral characteristic
They are eukaryotic and multicellular
Their cells have cellulose walls
Majority have transport system.
They have photosynthesis hence autotrophic.
Reproduction is both asexual and sexual
They show alternation of generation
This kingdom is divided into three divisions namely Bryophyta, Pteridophyta and Spermatphyta.
1. Division Bryophyta
These include mosses and liverworts.
General characteristic
They are thalloids as in liverworts or differentiated into simple-leaf like and stemlike structures
They lack vascular transport system
They contain chlorophyll hence photosynthetic.
They have developed rhizoids for anchoring and absorbing water together with dissolved mineral salts.
Show alternations of generations
Male gametes are produced by antheridia and female gametes by archegonia. Fertilisation depends on availability of water.
They are terrestrial growing on dump substratum eg rocks, walls and marshes
2. Division Pteridophyta
These include the ferns and horsetails. They show a greater variety and a greater ability than bryophyte.
General characteristics
They have roots, stems and leaves but no flowers
Leaves are compound with leaflets known as pinna.
They posses clearly defined vascular system( Having xylem and Phloem)
They show alternation of generations
Sexual reproduction
They have spirongira
Spermatophyta
3. Division Spermatophyta
This division comprises all the seed bearing plants. They are familiar green plants which produce seeds through flowers or cones.
General characteristics
The plant has roots, stems, leaves and seed bearing structures
They produce seeds
They have chlorophyll hence photosynthetic
They have vascular tissue is highly developed with xylem tissue consisting of both xylem tissue and tracheids.
The division spermatophyte consists of two main subdivisions:
Gymnospermatophyta
Angiospermatophyta.
Gymnospermatophyta
Characteristics
They bear cones of two types, male and female
After fertilization seeds are not enclosed in a fruit wall.
They show some xerophytic characteristics such as rolled leaves, needle-shaped leaves, sunken stomata and thick waxy leaves
Xylem consists mainly tracheids while phloem does not have companion cells.
This subdiviosn has three main classes
Class Coniferales
They include all the common gymnosperms naturally found in areas with little water.
They have needle-like shaped leaves with a thick waxy cuticle
Mature naked seeds occur at bases of female cones some months after pollination
Class Cycadales
Cycadeles resemble palms superficially.
They have long compound leaves which are clustered at the apex of a thick ussualy short and unbranched stems.
They have cones which are borne at the apex of the trunk among leaves.
Class Ginkgoales
Members of this class are very rare. They have deciduous with fan-like leaves. Examples include Ginkgo biloba species in china
2. Angiospermatophyta.
This is the most advanced group found almost everywhere. They include grasses, herbs, shrubs and trees.
Characteristics
They are flower bearing and are usually bisexual.
Seeds are enclosed in an ovary which develops into a fruit.
Xylem has tracheids and vessels while phloem has companion cells.
They exhibit double fertilization.
This group is divided into Two Classes
a) Class Dicotyledonae
These are plant whose embryo of seeds has two cotyledons.
Their leaves are broad and have networks of veins
Cross section of stems reveals vascular bundles arranged in rings
They have taproot system
Centrally placed star-shaped xylem with phloem alternating with arms of the xylem
Their flowers have floral parts in five or fours
Examples are herbs, shrubs, and trees. The herbs include plants with all stems such as beans, cabbages, tomatoes and black jack while the shrubs include plants with fairly thick stems such as coffee, tea and cocoa
b) Class Monocotyledonae
Their seeds have an embryo with one cotyledon
Relatively narrow leaves with parallel veins
The cross section of the stem reveals scattered vascular veins
No vascular cambium hence no secondary growth
They bear floral parts in threes
Examples include Maize, grass, wheat, sorghum, sugarcane, coconuts, bananas and sisal.