Kingdom Plantae: Definition, Overview, Classification, Characteristics, Examples

Overview Of Kingdom Plantae

Kingdom Plantae comprises one of the largest and most diverse classifications of multicellular organisms belonging to the eukaryotic domain and maximizes energy in the form of photosynthesis. The major responsibility that plants have in ecosystems is a producer role, and they make up the first and base level in the terrestrial trophic dynamics. The history of plant systematics started with descriptive approaches in the earlier days and is now in the age of Emerging Molecular Techniques for understanding phylogenetic relationships. Besides being the source of oxygen, food and shelter to various living organisms, plants are most useful to man in as far as crop production, in cure to diseases and as a balance to the ecological system. These details are crucial for the successful accommodation of biotic resources to cope with such issues as global warming and the deficit of species.

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Characteristics Of Kingdom Plantae

The characteristics are listed below-

General Characteristics

Plants in Kingdom Plantae share several fundamental characteristics that distinguish them from other organisms:

Multicellularity:

Flowers are made up of specialized multicellular cells forming tissues and organs.

Photosynthetic autotrophs:

They are mostly auto-digesting, they prepare their meals with the help of the green substance known as chlorophyll in photosynthesis.

Presence of cell walls composed of cellulose:

The plant cells are covered by a cell wall mainly containing cellulose to provide rigidity and protection to the cell.

Chlorophyll types a and b:

These also have chloroplasts algal coloured chlorophyll a and b to enable the light to be absorbed by the plant thus the green colour.

Reproductive Features

Alternation of generations

Plants exhibit a life cycle characterised by alternation of generations, involving two distinct multicellular phases: and comprises, in this context, the haploid gametophyta and the mainly diploid sporophytal component of the plant body. The phase that is prevalent in the life cycle called gametophyte produces gametes through mitosis; a fusion of egg and sperm, and the zygote is formed. It differentiates into the sporophyte and these sporophytes produce the haploid spores through meiosis. Such gametophytes grow into new gametophytes and as such the lifecycle of the plant is completed.

Types of reproduction:

Sexual Reproduction: Refers to the forced combination of gametes brought by the gametophytes and this causes variation in offspring.

Asexual Reproduction: This happens in a manner that involves fragmentation, budding or formation of reproductive structures like the bulbs and tubers, which in turn will form plants without fusion.

Physiological Processes

Plants engage in several crucial physiological processes that sustain their growth, development, and interaction with the environment:

Photosynthesis

Chlorophyll and the parts called chloroplasts in plants enable light energy to be changed into a chemical form, glucose, which the plant uses for energy and the byproduct of this process is oxygen. Photosynthesis is important for getting energy for the metabolic activities of plants and for the synthesis of oxygen expedited in aerobic respiration by living beings.

Respiration

Through cellular respiration plant cells can split glucose molecules and free energy for use in other cellular processes. This process called cellular respiration takes place in the mitochondria where oxygen is used in the process and carbon dioxide and water are formed as wastes. Regulation assists in the growth, development, and reproduction of plants throughout the process of respiration.

Transpiration

Stomata on the leaves of plants enable the process of releasing water vapour into the surroundings. I have learnt that it aids in controlling temperature, water uptake by the plant and absorption of other minerals from the ground. Also, transpiration generates a pressure that encourages movement of water and nutrients from roots to the shoots promoting plant development and nutrient distribution.

Classification Of Kingdom Plantae

The classification is listed below-

Non-Vascular Plants

Some plants that do not possess specialized tissues for conduction are Bryophytes which include Mosses liverworts, and hornworts. Most of them can be described as subshrubs growing near the ground and smaller than shrubs.

Bryophytes: Mosses, Liverworts, and Hornworts

Characteristics:

Thus, bryophytes do not possess true roots, stems and leaves though some of them contain stem and leaf-like structures. They even draw in water and nutrients by directly penetrating their cell walls as well as tissues. They do not possess seeds, but spores as their means of reproduction.

Lifecycle:

All bryophytes are characterized by dominance of the gametophytic generation in which the haploid gametophyte forms gametes (eggs and sperm) by mitosis. Because of the formation of the diploid zygote, a sporophyte is formed which is connected to the gametophyte. The sporophyte forms haploid spores through meiosis and these spores when released and occur, develop into new gametophytes.

Vascular Plants

Tracheophytes are vascular plants that contain vascular tissues called xylem and phloem tissues that help in the movement of water, minerals and nutrients within the plant's body. The main group of this category includes ferns, gymnosomes and angiosomes which are more prominent in the terrestrial society than the plant vascular since they have the potential to grow bigger and more diverse than the others.

Tracheophytes: Ferns, Gymnosperms, and Angiosperms

Characteristics:

May also have true roots, stems and leaves but the lack of seeds and flowers or the branching system is quite simple. They bear vascular tissues including the xylem which transports water and the phloem which helps in the transport of nutrients in a well-coordinated manner. They are disassembled by spores in the case of ferns and seeds in the case of gymnosperms and angiosperms.

Lifecycle:

Vascular plants have a strong sporophyte generation, the diploid sporophyte is the main life form in vascular plants. They reproduce either by spores or seeds and breed through meiosis and are also spread to new areas. This process goes through the development in which spores form a gametophytic phase that produces gametes; eggs and sperm. Fertilization leads to the formation of a zygote which thus forms a new sporophyte thus ending the life cycle.

Detailed Classifications

Bryophyta: Mosses

Characteristics: Mosses are such plants which do not have the vascular system and other organs as true roots, stems or leaves rather they possess some filamentous and thallose structures. They usually have low-growing, tufted to matted habits in appearance. Mosses are bisexual and reproduce through the formation of spores in capsules at tips of stalks called setae which are formed from the gametophyte plant.

Pteridophyta: Ferns

Ferns are among the vascular plants that have true roots, stems (rhizomes), and leaves (fronds). They reproduce through spores and the spore-producing structures or sporangia are found on the surface of fronds, particularly the undersides. Most ferns usually have a highly developed sporophyte generation in them.

Gymnosperms: Conifers

Gymnosperms are vascular plants which produce seeding apparatuses on cones or conelike structures Gymnosperm is derived from the Greek words gyms (nut) and sperma (seed) which literately means seed with a naked condition. It has needle-like or scaly leaves and these plants are found in areas ranging from the boreal to the desert. Some of these conifers are pines spruces, and cypresses as well.

Angiosperms: Flowering plants

Angiosperms are plants with seeds and fruits that are protected by special covers called seeds. Angiosperms have flowers for fruitful purposes intended for sexual reproduction attracting insects, birds and mammals. Angiosperms have numerous forms of adaptations and are the biggest class of plants in the world.

Chart representing the Plant classification.

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