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The structural characteristics of the parts of a plant vary by its functional requirements. For instance, the demands of the roots will not be the same as that of the stem. This functional priority is attributed to the tissue and the cells within it. When different types of tissues perform a single function, it creates a tissue system.
Plant organs like leaves and stems are made of huge collections of tissues. When these plant organs combine to perform a task, it is regulated by a system. Studying the function of the parts of a plant with its tissue and organ system helps us understand plant anatomy.
What are the types of plant tissues?
Plant tissues classify into two main types:
Meristematic tissue
2. Permanent tissue (non-meristematic cells)
Meristematic cells can divide and keep growing. They are usually located on the tips of a plant. After some time, meristematic cells mature and do not divide. Thereby becoming the permanent cells. Depending on the cell type, permanent cells are divided into:
Simple cells – These consist of cells that carry a single function. Functions of single cells include support and protection of the plant. There are three subtypes of simple cells, viz. Parenchyma, Collenchyma and Sclerenchyma.
Parenchyma – These cells are living cells and walled, soft in nature due to the presence of thin-walled cells.
Collenchyma – These cells are characterized by uneven thick-walled living cells.
Sclerenchyma – They have cells with thickened lignified walls, providing them strength and making them waterproof.
Complex cells – These cells carry complex functions. They transport water and food across the plant with the help of Xylem and Phloem.
Xylem: Xylem tissues are the tubular-shaped structure, with the absence of cross walls. It consists of tracheids, vessels, xylem parenchyma, xylem fibres.
Phloem: Phloem tissues are tubular-shaped, elongated, structures with the presence of walls with thin sieve tubes. It consists of sieve tubes, companion cells, phloem parenchyma, phloem fibers.
What are plant tissue systems?
The three plant tissue systems are present in the tissue system of the plant anatomy. They are categorised based on the location and the functions of the cell types. The types are as follows:
Epidermal tissue system – It makes up the outer layer of the plant.
Vascular tissue system – It is responsible for transportation inside the plant.
Ground tissue system – It comprises all the other tissues except the Dermal and Vascular tissues.
Dermal tissue system
This outer layer is to protect the plant from exterior harm. The dermal tissues are of 2 types, viz. the Epidermis and the Periderm.
The Epidermis is found on the leaves, fruits and flowers and in young plants. It is usually a single layer of tissue covering the internal cells of the plants, like a skin layer protecting the internal tissues.
Epidermal tissue has a few interesting tissue system examples. For instance, the Stomata on the lower surface of the leaves are minuscule openings on the bottom of the leaves for gas exchange. Another tissue system example is the Cuticle. It is a protective film on top of the leaves. It protects from over transpiration.
The periderm tissue system is found in the bark of tree trunks and hard surfaces. These are cork cells that result from secondary growth. It is a multilayered tissue, unlike the epidermis layer. It protects the plant from water loss and injuries.
Vascular tissue system
Xylem and Phloem are the main components of the vascular tissue system. Xylem handles water transportation across a plant, while Phloem handles the distribution of food and nutrients to all plant parts.
Some of the vascular bundle styles found in the plant cross-section are as follows,
Radial bundles- Radial bundles are when Xylem and Phloem are in a circular pattern on different radii. Tissue system examples for these bundles are the tissues in a plant’s roots.
Conjoint bundles- Conjoint bundles are when Xylem and the Phloem are in a bundle on the same radii. Xylem is toward central space, and the Phloem covers the outer periphery. It is an open bundle if the cambium is present between Xylem and Phloem. If the cambium is absent, it is a closed bundle.
Concentric bundles- Concentric bundles are when Xylem and Phloem alternate from the exterior to the interior and vice versa.
Ground tissue system
All tissues except the epidermal and vascular tissues are included in Ground tissue systems. These produce compounds that store food. They do photosynthesis if chlorophyll is present.
The ground tissue system has simpler tissue cells like parenchyma to store food. Collenchyma is another type of cell whose function is to provide elasticity to the cells when the secondary cells are not rigid. These protect plants from breaking. Tissue system examples for these are tendrils and climbers. Sclerenchyma, another type of ground tissue system, is the source of rigidity in the plants. It holds the plant in shape and protects the exterior cells from collapsing.
Plant organ system
Cells are the smallest units of plant structures. Cells of the same functions are together to create a clump of cells called tissue. When different tissues combine to perform a common function, they become an organ. When these organs work together, they create an organ system.
Organ system examples are the shoot and root systems. The shoot system is the upper part of the plant that consists of the leaves, flowers, buds and fruits. It is the part responsible for photosynthesis. On the other hand, the root system is the part that grows below the ground and handles water and nutrient absorption in plants.
Conclusion
Every plant has four main functions: absorbing water and nutrients from the soil, transporting absorbed water and nutrients to the shoots, producing food through photosynthesis and storing the prepared food. These functions are performed by simple and complex cells present in the tissues. The tissues at different locations make up the tissue system, which performs necessary functions. The tissue system allows plants to carry out primary functions at the best rate. It is built on a network of simple and complex cells. There are three plant tissue systems, viz. Dermal, Ground and Vascular systems.
