Like animal tissues, plant tissues are the basic building blocks of plants. They are collections of cells that work together to perform specific functions. These tissues, primarily involved in plant growth, development and survival, are divided into meristematic and permanent tissues.
Meristematic Tissues
Areas where cells are actively dividing are called meristematic tissues. It is up to them to make the plants grow. These tissues, which fall into three primary types, are found in areas referred to as meristems:
1. Apical meristems
The tips of roots and shoots are home to apical meristems. Primary growth that extends the plant is carried out by these regions. Undifferentiated cells in apical meristems divide rapidly, enabling roots to go deeper into the ground and shoots to reach higher in search of sunlight. Plants need this growth to search for resources such as light, water and nutrients, which give them a competitive edge and ensure their survival.
2. Lateral meristems
Secondary growth, which thickens the plant, is caused by lateral meristems, which direct the length of roots and stems. The two primary forms of lateral meristems are vascular cambium and cork cambium. The production of new xylem and phloem layers by the vascular cambium improves the plant’s ability to move sugars, nutrients, and water. Bark is the protective outer layer produced by the cork cambium. For woody plants, secondary growth is very important because it gives them structural support and allows them to grow larger and taller.
3. Intercalary Meristems
At the base of leaves, or internodes (the spaces between leaf axils), are intercalary meristems. Grasses and other monocot plants are key species that have these meristems, which help them grow quickly and recover from damage such as herbivorous grazing. When the apical meristem is destroyed or removed, the meristems help the leaves and stems grow longer, allowing the plant to continue growing. This ability ensures that plants can maintain growth and productivity, which is particularly beneficial in environments where physical damage is frequent.
Meristems give rise to rapidly differentiating, specialized cells that eventually become permanent tissues. These cells adopt specific functions and become incapable of further proliferation. They can be divided into three primary types: ground tissue, vascular, and dermal.
Permanent Tissues
Permanent tissues are formed when cells differentiate from meristematic tissues. Instead of dividing, these cells become specialized to perform specific tasks. Simple and complex tissues are additional classifications for permanent tissues.
Dermal Tissue
The plant’s dermal tissue covers and shields it. The outermost layer of cells, known as the epidermis, acts as a barrier to keep pathogens and environmental stressors out. By means of organs like trichomes and stomata, it also controls gas exchange and water loss.
Vascular Tissues
Vascular tissue transports water, minerals and sugars to different parts of the plant. It is a complex tissue with many cell types. Vascular tissue can be divided into:
1. Xylem
Responsible for moving nutrients and water from the roots to other parts of the plant. It is composed of different types of cells like xylem fibers, xylem parenchyma, vessel elements and tracheids.
2. Phloem
Moves sugars, the end product of photosynthesis, from leaves to other parts of the plant. Sieve tube elements, companion cells, phloem fibers, and phloem parenchyma make up the phloem.
Ground Tissue
In addition to serving as a site for photosynthesis, ground tissue also helps store carbohydrates and water. Ground tissue is composed of three types of cells:
1. Parenchyma
These are the most common plant cells, characterized by their large central vacuole and thin walls. Functions of parenchyma cells include tissue repair, storage, and photosynthesis.
2. Collenchyma
Collenchyma cells provide flexible support for growing plant segments due to their thick cell walls. They are primarily found in leaves and stems.
3. Sclerenchyma
The walls of these cells are thick and lignified, giving them rigidity and strength. These cells can be classified as sclereids or fibers, both of which are involved in the support of mature plant parts.
Conclusion
Knowing the tissues of plants is important to understand how they form, grow, and adjust to their surroundings. Each type of tissue has a unique function to maintain the general health and function of the plant. Plant tissues cooperate to support life and promote growth through the active division of meristems, the protective function of skin tissues, the transport mechanisms of vascular tissues, or the support and storage roles of ground tissues.
