The Kingdom Plantae 1
7. The Plant Kingdom (Plantae) - 1
Introduction
Plants are multicellular photosynthetic producers of biosphere. With the help of protists and fungi, plants provide the oxygen we breathe. The plant kingdom consists of 260,000 known species of mosses, liverworts, ferns, herbaceous and woody plants, bushes, vines, trees etc.
The land plant belongs to two major divisions Bryophytes & Tracheophytes.
Plants are multicellular photosynthetic producers of biosphere. With the help of protists and fungi, plants provide the oxygen we breathe. The plant kingdom consists of 260,000 known species of mosses, liverworts, ferns, herbaceous and woody plants, bushes, vines, trees etc.
The land plant belongs to two major divisions Bryophytes & Tracheophytes.
Bryophytes
Bryophytes are non vascular
embryo bearing plants consisting of three plant divisions: Bryophyta (Mosses), the Hepatophyta(liverwort) and the Anthocerophyta(Hornworts). Mosses cannot transport fluids though their bodies. Instead, they must rely on surrounding moisture to do this job for them. They reproduce by spores, never have flowers, and can be found growing on rocks, and on other plants. All species of bryophytes are characterized by the alteration of generations. The embryo from the sexual plant matures into a small asexual plant that remains attached to and dependent on the sexual plant. The asexual plant produces spores produced by lower plants, and they are spread by wind and other carriers to produce new sexual plants. Sterilized peat moss is used for surgical dressings.
Bryophytes are non vascular
embryo bearing plants consisting of three plant divisions: Bryophyta (Mosses), the Hepatophyta(liverwort) and the Anthocerophyta(Hornworts). Mosses cannot transport fluids though their bodies. Instead, they must rely on surrounding moisture to do this job for them. They reproduce by spores, never have flowers, and can be found growing on rocks, and on other plants. All species of bryophytes are characterized by the alteration of generations. The embryo from the sexual plant matures into a small asexual plant that remains attached to and dependent on the sexual plant. The asexual plant produces spores produced by lower plants, and they are spread by wind and other carriers to produce new sexual plants. Sterilized peat moss is used for surgical dressings.
Tracheophytes (Vascular Plants)
The characteristic organs of vascular plants are roots, stems and leaves and have vascular tissue xylem, which conducts water and minerals from ground to stems and leaves and phloem which conducts food produced in the leaves to stems, roots and storage and reproductive organs. Vascular plants are divided into Ferns (vascular plants without seed), gymnosperm ( seeds without fruit) and angiosperms(fruit & seed).
Ferns
The characteristic organs of vascular plants are roots, stems and leaves and have vascular tissue xylem, which conducts water and minerals from ground to stems and leaves and phloem which conducts food produced in the leaves to stems, roots and storage and reproductive organs. Vascular plants are divided into Ferns (vascular plants without seed), gymnosperm ( seeds without fruit) and angiosperms(fruit & seed).
Ferns
Ferns allies have a vascular system to transport fluids through their bodies but like mosses, they reproduce from spores rather than seeds. Three other phyla are included are The horsetails, club mosses and whisk ferns.
Gymnosperms( Conifers and Allies )
The gymnosperms add the next level of complexity to plant evolution: They reproduce from seeds instead of spores. The seeds however are “naked” not covered by an ovary. Usually the seed is produced inside a cone like structure such as a pine cone hence the name “conifer.” Conifers are fairly easy to identify. In addition to these cones trees and shrubs have needle-like, scale-like or awl-like leaves and they never have flowers. Approximately 600 species are counted as conifers including the pines, firs, spruces, cedars, junipers and yew. Species within the conifer ranks give us pine nuts, turpentine and rosin are prepared from pine resin. Pine seeds are eaten by man and animals. Ephedrine, a drug from Ephedra, is used for the relief of asthma and other respiratory ailments.
Angiosperms ( Flowering Dicot Plants )
Angiosperms add the final improvement to plant reproduction: They grow their seeds inside an ovary (Greek : angeion = vessel) which is, itself, embedded in a flower. After it is fertilized, the flower falls away and the ovary swells to become a fruit. The angiosperms are classified as Monocotyledons and Dicotyledons.
- Monocotyledons: Monocots have only one seed leaf in the embryo. The main veins of their foliage leaves are usually unbranched and nearly parallel to each other. These include orchids, lilies, rises, palms, grasses, bamboo and sugarcane. Monocots provide us with our primary sources of nutrition, supplying us and the animals we eat with grains such as wheat, oats and corn as well as fruits such as dates and bananas.
- Dicotyledons: Angiosperms in this class grow two seed-leaves(cotyledons). In addition, foliage leaves typically have a single, branching, main vein originating at the base of the leaf blade, or three or more main veins that diverge from the base. The vast majority of plants are Dicots. Most trees, shrubs, vines and flower belong to this group of around 200,000 species. Most fruits, vegetables, legumes and all the hardwood tree species come from this class.
Photosynthesis
It is a process by which green plants and certain other organisms use light energy to convert carbon dioxide and water to simple sugar glucose. In doing so, it provides the basic energy sources for all organisms and releases oxygen on which most organisms depend. Photosynthesis occur in green plants, seaweeds, algae and certain bacteria. Plant photosynthesis occurs in leaves and green stems within specialised cell structures called chloroplasts. The chloroplast is divided by membranes into numerous disk shaped compartments called thylakoids . These are arranged vertically in the chloroplast like a stack of plates is called a granum; the grana lie suspended in a fluid known as stroma. Embedded in the membranes of the thylakoids are hundreds of molecules of chlorophyll, a light trapping pigment required for photosynthesis. Minute structures called plastids contain the chlorophyll within the leaf. The chloroplast traps light energy and covert it into a chemical energy contained in nicotinamide adenine dinucleotide phospate (NADPH) and adenosine triphosphate(ATP),two molecules used in the second stage of photosynthesis. In the second stage, called the light independent reaction, NADPH provides the energy for this and other reactions used to synthesize glucose. The carbohydrates manufactured in the leaves of higher plants are distributed to roots and storage organs along phloem. This long distance movement of organic compounds is called translocation. Sucrose is the principal form in which the carbohydrates are translocated.
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