A Short Note on Plantae

Plants are Eukaryotic organisms and are autotrophic. Plants contain chloroplast and a cellulose cell wall. Though plants are generally autotrophic and synthesize their own food some plants belonging to the category of insectivores are heterotrophic. Some examples are Bladderwort and Cucuta are parasites.

History 

The concept of the Plant kingdom was given by Whittaker in the year 1969. According to this classification, he divided the organism into five major kingdoms. These are as follows -:

1. Kingdom Monera
2. Kingdom Protista
3. Kingdom Fungi 
4. Kingdom Animalia
5. Kingdom Plantae

Kingdom Plantae is also known as the Plant Kingdom. Earlier classification has divided organisms based on the presence of cell walls. So According to that criteria Fungi, Monera and Protista are included in the same Kingdom that is Plantae but now these are excluded from these criteria. Based on the current classification the Plant kingdom includes the following divisions -:

• Algae
• Bryophytes 
• Pteridophytes
• Gymnosperms
• Angiosperms

Algae 

Algae are chlorophyll-containing and autotrophic organisms. Some of the major characteristics of this division are as follows-:

• They are the simplest division in the plant kingdom.
• They are mainly aquatic in nature and can be either freshwater or marine.
• They are found in a variety of habitats like wood, soil and stones etc.
• They have a symbiotic association with fungi. For example in the case of lichen – a symbiotic association of fungi and algae and with animals like the sloth bear.
• The size is diverse as it includes unicellular forms like Chlamydomonas to gregarious and colonial forms like Volvox 
• Some are filamentous Spirogyra.
• Marine forms such as Kelps also belong to this category.
• The mode of reproduction in Algae is- sexual, asexual and vegetative forms.
• Vegetative reproduction takes place in the form of fragmentation.
• Sexual reproduction takes place through fertilization which is a fusion of gametes. The gametes can be similar in size – then they are called isogamous, or can be dissimilar – known as anisogamous.
• Uses of algae are in food supplements for space Programmes, in making ice cream and jellies.
• Algae can be divided into these three categories -: Chlorophyceae, Phaeophyceae and Rhodophyceae.
• Some examples of Chlorophyceae or green algae are – chara and Chlamydomonas.
• Examples of Phaeophyceae or brown algae are – fucus and sargassum.
• Examples of Rhodophyceae or red algae are – gracilaria and Porphyra.

Bryophytes 

They are called amphibians of the Plant Kingdom. The plant body is more developed as compared to algae. Some of the characteristics of this group are as follows -:

• Absence of true roots, stem and other plant features.
• Presence of either multicellular or unicellular rhizoids.
• The plant body is a haploid.
• The sex organs in Bryophytes are multicellular.
• The male gamete is called antheridium.
• The female gamete is called archegonium.
• The dominant stage in the life cycle is the gametophytic stage.
• Some important uses of Bryophytes are some species of sphagnum are used to make peat and some mosses are the pioneer species in some environment setups.
• Bryophytes are divided into two categories these are – Liverworts and Mosses.
• Liverworts are shade-loving organisms where the plant body is thalloid. The reproduction is asexual with the help of structures like gemmae. An example of Liverworts is Marchantia 
• Mosses- They reproduce with the Help of vegetative means like budding and fragmentation. Some examples of mosses are Funaria, Sphagnum etc.

Pteridophytes 

These are terrestrial planets with vascular structures. They are found in damp and shady areas. Some of the major characteristics of pteridophytes are as follows-:

• They grow well in sandy soil.
• They have true roots and other plant structures, unlike Bryophytes.
• They have xylem and phloem.
• They are soil binding plants.
• They are used for medicinal purposes.
• They have diversity in leaf structure, with small leaf structures known as microphyll and large leaf structures known as microphyll.
• The main body is the sporophyte.
• Some of the examples of pteridophytes are – ferns, Salvinia, Selaginella, Equisetum, Pteris and so on.
• Pteridophytes are further divided into four categories these are – Psilopsida, Lycopsida, Sphenopsida and Pteropsida.

Gymnosperms 

The word gymnosperms word can be broken down into gymnos meaning naked and sperma meaning seeds. So, these are simply put those plants where the ovules that convert to seeds post maturation are not covered by the ovary wall.

Some of the major characteristics of gymnosperms are as follows-:

• The leaves of gymnosperms are adapted to adverse climatic conditions.
• For example – Confers have Needle shaped leaves to counter high temperatures and to reduce transpiration.
• They are heterotrophs.
• They produce cones. The cones bearing male spores – are microspores and female spores are megaspores.
• Some of the major examples of Gymnosperms are – Cycas, Pinus and Ginkgo.

Angiosperms 

They are also known as flowering plants. They are produced by fertilization and to be specific double fertilisation.

Some of the major characteristics of the angiosperms are as follows -:

• They vary in size from small structures like wolfia to big trees like Eucalyptus.
• They are formed by the fertilisation of pollen and ovules in the ovary.
• These plants are characterised by flowers.
• They can be divided into subcategories like the – dicots and monocots. 
• Like in a flower they have the male reproductive part the stamen which is the anther, filament and the pollen grain. Along the same lines the female reproductive part is known as the carpel or pistil and has stigma, style and ovary as the major parts .while the ovules are the female gamete.
• Pollination is present in this category.
• Some of the major examples are Wolfia, grass, and bamboo.

Conclusion 

The plant kingdom is a diverse category that was made with the Help of the five-kingdom classification of Whitaker. The plant kingdom is divided into the following categories as Algae, Bryophytes, pteridophytes, gymnosperms and angiosperms. Plants are an important part of the environment and have a social, economic, and aesthetic value attached to them. Hence the conservation of the plant biodiversity is crucial.