R.H. Whittaker introduced a new classification system for all living organisms, aiming to provide a comprehensive framework for understanding biodiversity. He classified organisms using characteristics such as cellular structure and nutrition. Body organization, reproduction, and phylogenetic relationships were important criteria. The five kingdoms are Monera, Protista, Fungi, Plantae, and Animalia. Based on the criteria, organisms were categorized into five groups. This article will discuss the plant kingdom known as Plantae.
Plant Kingdom – Plantae
Kingdom Plantae constitutes one of the principal biological kingdoms, specifically established to include the vast array of multicellular, eukaryotic organisms commonly referred to as plants. Organisms in Kingdom Plantae are notably eukaryotic and multicellular. A primary characteristic of these organisms is being autotrophic. As defining characteristics, plants are organisms which are eukaryotic, possessing a true nucleus, multicellular, composed of many cells, and autotrophic. A crucial structural feature of plant cells is their characteristic rigid cell wall, which provides essential support, protection, and maintains cellular shape and integrity. Plants are autotrophic organisms that produce their own food. They obtain this food through the process of photosynthesis. The key green pigment absolutely necessary for photosynthesis to successfully take place within the plant organism is definitively known as chlorophyll.
Characteristics of Kingdom Plantae
Indeed, the defining characteristic features associated with the diverse plant kingdom are quite numerous and varied, highlighting their unique biology and structure. A key characteristic of plants is that they are non-motile organisms, meaning they cannot move independently. These organisms function as autotrophs, a classification signifying their unique capacity to independently produce their necessary nourishment. Plants reproduce using varied methods, primarily categorized as either asexual reproduction, often including vegetative propagation, or through conventional sexual processes. These organisms are multicellular eukaryotes. Their cells contain a rigid outer cell wall. They also have a large central vacuole. Chlorophyll, the pigment found in plants, is essential as it captures light needed for photosynthesis. Within the plant organism, specialized structures carry out various distinct functions. Examples include structures for securing anchorage and offering physical support. The function of reproduction is carried out by specialized structures. The vital process of photosynthesis takes place in specialized structures.
Classification of Kingdom Plantae
The vast plant kingdom is systematically categorized into distinct subgroups established through the application of several key criteria.
Specific criteria are used when classifying the plant kingdom. These criteria also explain the basis for its classification. They detail the specific characteristics that are considered:
- The plant body: Whether the plant has a well-differentiated body with root, stem, and leaves is considered.
- The vascular system: Classification considers the presence or absence of xylem and phloem vessels used for transport.
- Seed formation: Classification relies on the presence or absence of flowers and seeds, and whether the seeds are naked or enclosed in fruit.
Based upon these important classification criteria, the diverse plant kingdom has now been categorized into five distinct subgroups. These five subgroups are the main divisions of the plant kingdom. The subgroups include Thallophyta, Bryophyta, and Pteridophyta. They also include Gymnosperms and Angiosperms in this classification.
Thallophyta
Thallophytes possess basic, uncomplicated body forms. Their plant body structure is called a thallus. Thallophytes do not have a well-differentiated plant body. It is not composed of roots, stems, and leaves.
Their structure is simply the thallus form. This thallus can appear filamentous or colonial. It can also be branched or unbranched. Examples of Thallophytes include different kinds of algae. This includes green algae, red algae, and brown algae. Specific examples are Volvox, Fucus, Spirogyra, and Chara. Other examples are Polysiphonia and Ulothrix.
Bryophyta
The group Bryophyta includes plant types such as mosses, hornworts, and liverworts. The characteristics describing the group Bryophyta include several key features. A key feature is that Bryophytes lack true vascular tissue. Their plant body has parts resembling roots, stems, and leaves. These parts are not true structures like roots, stems, and leaves. Bryophytes live on land, typically inhabiting damp and shady places. They are known as the ‘amphibians of the plant kingdom’. This is because water is essential for their sexual reproduction. Some examples of Bryophytes are Marchantia, Funaria, Sphagnum, and Antheoceros.
Pteridophyta
The characteristics describing the group Pteridophyta include several key features. Yes, the plant body of Pteridophytes is well-differentiated. It is clearly divided into true roots, stems, and leaves. A vascular system is present for water and substance transport. Some examples of Pteridophytes include Selaginella, Equisetum, and Pteris.
Gymnosperms
Gymnosperms have a plant body clearly divided into true roots, stems, and leaves. They also possess vascular tissues for internal transport. A unique characteristic is their naked seeds. These seeds are not enclosed within any fruit. Some examples include Cycas, Pinus, and Ephedra plants.
Angiosperms
The characteristics describing the group Angiosperms include several key features. Angiosperms are seed-bearing vascular plants with a well-differentiated plant body. Their plant body is clearly divided into roots, stems, and leaves. These plants possess vascular tissue which helps transport water and nutrients. A key characteristic is that Angiosperm seeds are enclosed within fruits. Angiosperms are a group of plants found widely distributed across the globe. Their size varies greatly, from tiny to very large forms. Sizes range from small plants like Wolffia at 0.1 cm. Large examples include Eucalyptus trees around 100 meters tall. Further classification divides Angiosperms into monocots and dicots. This is based on the number of cotyledons present in seeds. Some examples are mango, rose, tomato, onion, wheat, and maize.
Cryptogams and Phanerogams
The plant kingdom is classified into two main groups. This is based on the presence or absence of flowers and seeds. These two main groups are called Cryptogams and Phanerogams. Cryptogams are non-flowering plants and do not produce seeds. This group includes Thallophyta, Bryophyta, and Pteridophyta subgroups. In contrast, Phanerogams are flowering and seed-bearing plants. The Phanerogam group includes the Gymnosperm and Angiosperm subgroups. So the key difference lies in flower and seed production.
FAQs
What is the name of the pigment responsible for photosynthesis in plants?
The role of chlorophyll in plants is to enable them to carry out photosynthesis. This means chlorophyll does perform photosynthesis in plants by capturing light energy. Chlorophyll is the pigment responsible for photosynthesis in plants. Chlorophyll is indeed responsible for photosynthesis in plants.
What are the criteria used for the levels of classification in plants?
Classification levels for plants use three main criteria. The first is the structure of the plant body. This checks for differentiation into roots, stems, and leaves. Another criterion is the presence or absence of a vascular system. Thirdly, characteristics regarding seed formation are used. This includes if flowers and seeds are present. Also, if seeds are naked or enclosed in fruit.
What are the characteristics of Thallophytes?
The plant group lacking a well-differentiated body structure is the Thallophyte category. If a plant body is not well-differentiated, it lacks clear divisions. This means it is not structured into distinct stem, leaves, or roots. Plants within the Thallophyte category do not have a clearly divided body. Their body is not differentiated into stem, leaves, and roots.
What are the significant features of Gymnosperms?
Gymnosperms possess a well-differentiated body structure and vascular tissues. They have a body clearly divided into roots, stems, and leaves. They also possess vascular tissues for internal transport. What is unique about Gymnosperm seeds is they are naked. Their seeds are not enclosed within any kind of fruit. Therefore, Gymnosperm seeds do not have a fruit covering. These plants are called Gymnosperms because their seeds are naked. The term Gymnosperm comes from Greek words meaning “naked seed.” Specifically, “gymno” means naked, and “sperma” means seed.
What are the characteristics of Angiosperms?
Angiosperms are a group of plants characterized by several features. As part of their life cycle, Angiosperms produce seeds. These seeds are contained inside protective fruit structures. Angiosperms have a body structure clearly divided into roots, stems, and leaves. They develop flowers at some point during their existence. Angiosperms are classified into two main kinds called monocotyledons and dicotyledons.