Kingdom Plantae

The first level of classification among plants depends on whether the plant body has well-differentiated, distinct parts. The next level of classification is based on whether the differentiated plant body has special tissues for the transport of water and other substances. Further classification looks at the ability to bear seeds and whether the seeds are enclosed within fruits.

THALLOPHYTA

• Plants that do not have well-differentiated body designs fall into this group.
• The plants in this group are commonly called algae.
• These plants are predominantly aquatic.
• Examples are Spirogyra, Ulothrix, Cladophora, Ulva, and Chara.

BRYOPHYTA

• These are called the amphibians of the plant kingdom.
• The plant body is commonly differentiated to form stem and leaf-like structures. However, there is no specialized tissue for the conduction of water and other substances from one part of the plant body to another.
• Examples are moss (Funaria) and Marchantia.

PTERIDOPHYTA

• In this group, the plant body is differentiated into roots, stem, and leaves and has specialized tissue for the conduction of water and other substances from one part of the plant body to another.
• Some examples are Marsilea, ferns, and horsetails.
• The reproductive organs of plants in all
  these three groups are very inconspicuous,
  and they are therefore called ‘cryptogams’, or
  ‘those with hidden reproductive organs.'
• On the other hand, plants with well-differentiated
  reproductive parts that ultimately make seeds are called phanerogams.
• Seeds are the result of the sexual reproduction process. They consist of the embryo along with stored food, which assists in the initial growth of the embryo during germination.

This group is further classified, based on whether the seeds are naked or enclosed in fruits, giving us two groups:

• Gymnosperms
• Angiosperms.

 GYMNOSPERMS

• This term is derived from two Greek words: 'gymno' means naked and 'sperma' means seed.
• The plants of this group bear naked seeds and are usually perennial, evergreen and woody.
• Examples are pines and deodar 

ANGIOSPERMS

• This word is made from two Greek words: angio means covered and Sperma – means seed. These are also called flowering plants.
• The seeds develop inside an ovary which is modified to become a fruit.
• Plant embryos in seeds have structures called cotyledons. Cotyledons are called ‘seed leaves’ because in many instances they emerge and become green when the seed germinates.

The angiosperms are divided into two groups on the basis of the number of cotyledons present in the seed.

• Monocotyledonous/monocots - Plants with seeds having a single cotyledon. 
• Dicots - Plants with seeds having two cotyledons.

• Eukaryote

• Multicellular (except thallophyta which can be unicellular)

• Autotrophic

• Cell wall present

• Classified into 5 subgroups -

  • CRYPTOGAMAE

    • Thallophyta

    • Bryophyta

    • Pteridophyta

  • PHANEROGAMS

    • Gymnosperms

    • Angiosperms

Classification is based on the following criteria:

• Plant body: if well-differentiated into Root, Stem, and Leaves.

• Vascular system: specialized vascular system i.e. e. Phloem and Xylem for the conduction of water and other substances from one part of the plant body to another are present or not.

• Seed formation: Presence or absence of flowers and seeds, and if the seeds are naked or enclosed in a fruit.

I. Cryptogamae:

Cryptogamae (hidden reproductive organs) - have naked embryos that are called spores.

1) Thallophyta:

• Commonly called algae

• Maybe unicellular or multicellular

• Do not have a well-differentiated body

• Predominantly aquatic (freshwater or marine)

• They have a soft, fiber-like body.

• Examples are Spirogyra, Ulothrix, Cladophora, and Chara

2) Bryophyta:

• These are called the amphibians of the plant kingdom.

• They are multicellular.

• Body differentiated to form the stem and leaf-like structures.

• No specialized vascular tissue

• The body is flat, ribbon-like

• These plants reproduce asexually by spore-formation and sexually by zygote formation.

• Examples are moss and Marchantia
  

3) Pteridophyta:

• The plant body is differentiated into roots, stem, and leaves

• Has specialized vascular tissue for conduction

• Examples are Marsilea, ferns

II. Phanerogams:

Phanerogams - well differentiated reproductive tissues that make seeds

1) Gymnosperms:

• Naked seed

• Usually perennial, evergreen and woody.

• Their stems are without branches

• They do not form fruits.

• Examples are pines, cycas, etc

2) Angiosperms:

• Covered seeds

• Also called flowering plants

• Plant embryos in seeds have structures called cotyledons.

• On the basis of these cotyledons, they are divided into two groups on the basis of the number of cotyledons present in the seed.

  • Monocots

  • Dicots