Kingdom Plantae: what is it, characteristics, classification and examples

The Plantae kingdom, also known as plant kingdom , is one of the five kingdoms taxonomic existing ( kingdom Animalia , Plantae kingdom, kingdom Fungi , Kingdom Monera and kingdom Protista ) and consists of multicellular organisms, eukaryotes, which perform photosynthesis . It includes all terrestrial plants, aquatic plants and some species of algae . It is made up of more than 390,000 known species, making it the second largest kingdom.

The appearance of plants on Earth took place in the Ordovician, although it is thought that the first algae-type plants could have appeared more than a billion years ago. It is a group with a long evolutionary history, which has resulted in an enormous diversity of morphologies and adaptations for the survival of these organisms, so essential for life on the planet.

In general, plants present a series of characteristics in common, although they do not always occur all in the different species, since, for a living being to be considered as a plant, its evolutionary lineage is more important than its characteristics. These are the main characteristics of the kingdom Plantae :

• They are multicellular and eukaryotic organisms.
• They are primarily sessile and live attached to the substrate. Due to this, they have developed defense mechanisms such as the production of toxic substances in leaves, flowers or fruits.
• They are photosynthetic organisms, so they use energy from sunlight and atmospheric carbon dioxide to synthesize nutrients, converting CO2 and water into sugars and oxygen.
• Some plants have evolved and developed other ways of feeding other than photosynthesis. There are species that are parasitic and feed on the nutrients of other plants.
• Its plant cells (eukaryotes) have a special structure that has a cell wall composed of pectin and cellulose, as well as a large central vacuole.
• Plant cells have special organelles called chloroplasts that contain a photosynthetic pigment called chlorophyll and where photosynthesis takes place.
• Plants are the largest producers of oxygen and regulate the amount of carbon dioxide in the atmosphere.
• Plants act as the basis of the trophic chain in almost all ecosystems and their ecological activity is decisive in various chemical cycles.
• They reproduce sexually and asexually. Their reproductive organs generate multicellular embryos.
• They have a life cycle with generational alternation in which two phases alternate: a generation of haploid gametophyte and another of diploid sporophyte.
• They have an enormous capacity to adapt to the various environmental conditions of the different existing ecosystems, such as high temperatures and the remarkable aridity of deserts or the cold of the poles.

Plants can be classified in several ways. One of the most common forms of classification of the Plantae kingdom is according to whether they have flowers or lack them.

Plants without flower

Flowering plants are divided into three groups: thalophytes, bryophytes, and pteridophytes.

• Thalophytes (algae): simple, autotrophic and non-vascular plants. They have unicellular sex organs and do not form an embryo. Depending on the habitats in which they grow, specialized forms appear such as cryophytes (they live in snowy and icy areas), thermophytes (in hot waters), epiphyses (they develop on other plants) or endophytes (they grow inside other plants). plants).
• Bryophyte plants: they are the simplest and most primitive land plants. Typically, they occupy humid and shady habitats, although others thrive in extremely arid or watery conditions. They reproduce sexually; They have a male sexual organ called antheridium and another female called archegonium. Bryophyte plants are characterized by having stems and leaves but lacking roots. Instead, they have structures known as rhizoids attached to the surface by which they absorb water and minerals. Expand this information with this post about Bryophytes plant: examples and characteristics .
• Pteridophyte plants: they are mostly terrestrial plants that occupy shady areas and are characterized by lacking seeds and flowers, although the leaves produce spores through which new plants can be generated. The group is made up of four sub-phyla: Psilopsida (the oldest vascular plants, with a majority of fossil species), Lycopsida (differentiated body in root, stem and small leaves of a single simple vein), Sphenopsida (presents stem with knots and internodes) and Pteropsida (body differentiated in root, stem and megafill leaves). You can learn more about these in this link where you will see information about Pteridophyte Plants: what they are, types and examples .

If you want to learn more about Plants without flowers you can consult this other article.

Flowering plants

Also known as seed plants, flowering plants are divided into gymnosperms and angiosperms.

• Gymnosperms: they are the group of plants that do not have flowers or true fruits but do produce seeds, which are unprotected, visibly arranged on the leaves or on the stem and form cones or cones. They are woody plants, with arboreal appearance that have anemophilic pollination (by the wind) and dioecious (of separate sexes); furthermore, most are perennial. Here we give you more details about Gymnosperm Plants: what they are, characteristics and examples .
• Angiosperms: they are plants with flowers, fruits and seeds. They are the most abundant and ubiquitous plant type of vascular plants today. They present the ovules in hollow ovaries, which develop into a fruit and, within these, the ovules inside grow and give rise to the seeds. Angiosperms are differentiated into two large groups: monocots and dicots. The cotyledons are stores of the food necessary for the germination of the shoots.

Classification of the kingdom Plantae: angiosperms

To expand the information on Angiosperm Plants: what they are, characteristics and examples , we recommend this other AgroCorrn article. Anyway, in this part we clarify better the aforementioned differentiation between monocots and dicots.

• Monocots: the monocot plants are plants whose seeds have only one cotyledon. They have adventitious roots, simple leaves with parallel venation and trimeric flowers (their corolla has three petals or a multiple of three).
• Dicotyledons: plants whose seeds have two cotyledons. In addition, they have primary roots, leaves with reticulated venation, and tetrameric or pentameric flowers.

Within the kingdom of plants , we can find several examples in each of the existing types already mentioned:

• Thalophytes: Ulva lactuca , Asterella ludwigii .
• Bryophytes: Polytrichum commune , Bryum argenteum.
• Pteridophytes: Lycopodium clavatum , the eagle fern ( Pteridium aquilinum ), the horsetail ( Equisetum arvense ) .
• Gymnosperms: yew ( Taxus baccata ), white pine ( Pinus albia ), ginkgo ( Ginkgo biloba ).
• Angiosperms: Japanese flowering cherry ( Prunus serrulata ), sunflower ( Helianthus annuus ), aloe vera ( Aloe barbadensis ).

The importance of the plant kingdom lies in the important ecological roles they play.

• They are the primary source of oxygen as a result of their photosynthetic processes, these being key to maintaining the atmospheric levels of this gas. In turn, they control and regulate the levels of carbon dioxide in the atmosphere.
• Together with other photoautotrophic organisms, they act as the basis of the entire food chain in ecosystems, as they fix organic carbon from inorganic sources and serve as a food and energy source for all heterotrophic organisms in the ecosystem, which are incapable of generating their own food. and they depend on the production of organic matter by photosynthetic organisms.
• They play a role in various ecological cycles, such as nitrogen – since plants regenerate nitrogen in the soil and disperse it – and also sulfur.
• They are useful for human beings in several ways: they are a main source of food in agriculture (among the main plants cultivated for their consumption are rice, vegetables, fruits …); They can be given an industrial use and used to manufacture oils, pigments, paper, textiles, etc .; many also have medicinal properties and have been used for that purpose since ancient times.