The living organisms are divided into plants and animals according to the traditional biologists. In plant kingdom a systematic study of plants development, floral characteristics, dispersal, distribution, plants association, maxima, diseases, sustainability and vulnerability are examined.
The topography, terrain, climate, soils, bio-diversity, tectonic activities and land-use practices closely controlled the distribution of plants in the world. In general, the vegetation varies from equator towards poles, and from sea-level to altitudes.
The ecologists and bio-geographers divided the flora of the world into six major plant kingdoms in the world on the basis of floral characteristics i.e. Australian Kingdom; Cape Kingdom (South Africa); Antarctic Kingdom; Palaeo-tropical Kingdom; Neo-tropical Kingdom; Boreal Kingdom.
1. Australian Kingdom: The Australian floristic kingdom in Australia and its neighbouring islands and surrounding seas and oceans. The dominant species of trees in this kingdom are eucalyptus. According to one study, there are 600 species of eucalyptus in the world, out of which 75% are found in this region. The eucalyptus varies in characteristics and height from region to region. Eucalyptus has been dispersed in Australia by the Europeans from South America.
2. Cape Kingdom: The Cape Floral Kingdom stretches over the southern province of South Africa. The plants of this kingdom belong to the category of cryptophytes which bear buds in the form of bulbs and tubers which are buried in the soils. These bulbs and tubers give birth to other plants as new shoots come out from these bulbs and tubers and are developed as plants.
3. Antarctic Kingdom: The Antarctic floral kingdom stretches in the higher latitudes of the Southern Hemisphere including the Desert of Patagonia, southern parts of South Chile and New Zealand. The dominant plant of this zone is Southern Beech (Nothofagus). Its important grasses include Tussock Grasses and a few sedes (plants which grow in water).
4. Palaeotropical Kingdom: It was proposed by Ronald Good and Armen Takhtajan. This plant kingdom stretches over the greater parts of Africa, West Asia, South Asia, China and the countries of South Asia and South East Asia. There is great variation in floral species in the different parts of this zone. There are however, few plants common to all the parts of this floral kingdom.
5. Neo-Tropical Kingdom: The trees of this kingdom are developed about 130 million years back i.e. the Cretaceous Period. The original flowering plants were developed in South America. The vegetation of this kingdom ranges from tropical rainforest in the Amazon and Orinoco basins to open savanna in Venezuela (the Llanos) and Argentina (the Pampas) excluding the desert of Patagonia and southern parts of Chile.
6. Boreal Kingdom: It was identified by botanist Ronald Good and is stretched to the whole of Greenland, whole of Europe and Eurasia. This is one of the most extensive kingdoms of the floral kingdom. This floral kingdom includes the mosses, lichen and sedges. It is also the botanical analogue to an ecozone, which takes into account the distribution of animal as well as plant species.