Kingdom - Plantae

1.0Characteristics of Plants

(1) Plantae includes multicellular, eukaryotic organisms with cellulosic cell wall.

(2) A mature plant cell commonly possesses a single large central vacuole.

(3) Plastids are found in all plants. Some plastids possess photosynthetic pigment, such plastids are known as chloroplasts.

(4) Plants are autotrophic in nature because they are able to perform photosynthesis with the help of chlorophyll present in chloroplasts.

(5) Reserve food is starch.

2.0Classification of Plants

The first level of classification among plants depends on whether the plant body has well differentiated, distinct components or not. The next level of classification is based on whether the differentiated plant body has special tissues for the transport of water and other substances within it. Further classification looks at the ability to bear seeds and whether the seeds are enclosed within fruits.

Eichler (1883) divided the kingdom plantae into two subkingdoms, cryptogamae and phanerogamae.

Cryptogamae (Gk. cryptos–hidden, gamous–marriage): The reproductive organs are inconspicuous (not clearly visible). The embryo, if present is naked. They are also called lower plants, flowerless and seedless plants. There are three divisions in this subkingdom – Thallophyta, Bryophyta, Pteridophyta.

Phanerogamae (Gk. phaneros – visible, gamous – marriage): The plant which possess visible and well differentiated reproductive organs are called phanerogams. They have well differentiated and evident reproductive organs that ultimately make seeds. Therefore, they are also called seed bearing plants. Phanerogamae has single division spermatophyta.

Following plant groups are included in kingdom plantae -

1. Thallophyta 2. Bryophyta 3. Pteridophyta 

4. Gymnosperms 5. Angiosperms

Thallophyta

They are commonly called algae. Plant body is not differentiated into root, stem and leaves, therefore called thallus. These are aquatic (found in marine, fresh water and moist land). They do not have mechanical and conducting tissue.

e.g. green algae - Spirogyra, Ulothrix, Cladophora, Chara, Ulva.

Brown algae - Fucus; Red Algae - Gelidium, Gracilaria, Polysiphonia.

Bryophyta

Bryophytes are also known as amphibians of plant kingdom.

These are the simplest and the most primitive land plant.

They have flat plant body which differentiate into stem, leaf and root like structure (Rhizoids). Main plant body of bryophytes is gametophyte which is attached to substratum by means of rhizoids. Gametophyte: It is haploid plant structure which produce gametes directly.

Sporophyte lives as a parasite over it.

There is no specialized tissue for the conduction of water and other substances from one part of the plant body to another.

e.g. Liver wort - Riccia and Marchantia, Horn wort - Anthoceros, Moss - Funaria

Pteridophyta

Main plant body is sporophyte which is differentiated into root, stem and leaves. Sporophyte: It is diploid (with two sets of chromosomes) plant structure which produces haploid spores through the process of meiosis. Gametophyte is a small but independent stage in life cycle. Pteridophytes are called vascular cryptogams as they have vascular tissues. Vascular tissues (xylem and phloem) appear for the first time in pteridophyta and so they are also called vascular cryptogams.

• They produce spores inside sporangia.

• Male gametes need water for fertilization.

• Fruits and seeds are absent.

e.g. Selaginella (Club moss), Equisetum (Horse tails), Marsilea, Azolla (Water fern), Pteridium, Dryopteris (Ferns).

• The thallophytes, bryophytes and pteridophytes have naked embryos that are called spores. 

All of these have inconspicuous reproductive organs or hidden sex organ.

Spermatophyta or phanerogams are classified into two groups (Gymnosperm and Angiosperm) on the basis of naked or enclosed seeds.

Gymnosperm (Gymno-Naked and Sperma-Seeds)

Spermatophyta or phanerogams are classified into two groups (Gymnosperm and Angiosperm) on the basis of naked or enclosed seeds.

Plants are usually evergreen, woody and perennial. They are trees and shrubs.

Sporophylls are aggregated to form cones (male and female cones).

They bear naked seeds. The seeds are not enclosed inside fruits. Instead they lie exposed over the megasporophylls. Xylem lack vessels and phloem lack companion cells in gymnosperm.

E.g. Cycadae - Cycas,  Coniferae - Pinus (Pines), Cedrus (deodar), Ginkgo.

Angiosperm - (Angio - Covered and Sperma-Seed)

Plants are deciduous or evergreen, annual, biennial or perennial and they may be herbs, shrubs or trees. These are called flowering plant. Sporophylls are aggregated to form flowers. The plants of this group produce seeds inside an organ called ovary, which is modified into fruit. Embryo is present in the seed. Cotyledons are part of embryo, also called seed leaves, because in many instances they emerge and become green, when the seed germinates.

Flowers may be unisexual or bisexual. Pollination occurs by wind, water and animals. Endosperm is a new food storing structure which is generally triploid and is formed by fusion of three nuclei (triple fusion).

In angiosperms, a seed may have one or two cotyledons. On the basis of number of cotyledons present in the seed, angiosperms have been divided into two classes, dicotyledoneae (dicots) and monocotyledoneae (monocots).

Class - Dicotyledoneae

Angiosperms in which seeds possess two cotyledons are commonly called dicots or dicotyledonous plants. eg. Gram, Pea, Mustard, Ipomoea.

Class - Monocotyledoneae

Angiosperms, which have single cotyledon in their seeds. They are commonly called monocots or monocotyledonous plants. e.g. Lily, Coconut, Wheat, Maize, Grass, Bamboo, Paphiopedilum.

Note:- Embryophyta: Plants having an embryo stage in their life cycle. E.g.  bryophytes, pteridophytes and seed plants.

Tracheophyta: Plant group having vascular tissues. E.g. pteridophyta and spermatophyta.

In spermatophyta or phanerogams, fertilization occurs with the help of a pollen tube. An external water is not required. After fertilization plants produce seeds which contains embryo along with stored food. On germination each seed forms a new plant.

3.0Also Read