Plant Tissues PDF

 Plants are composed of three major organ groups: roots, stems, and leaves. These organs are comprised of tissues working together for a common goal (function). In this session, we will look at the various types of plant tissue and their place and purpose within a plant. Plant Tissue...

 Plants are composed of three major organ groups: roots, stems, and leaves. These organs are comprised of tissues working together for a common goal (function). In this session, we will look at the various types of plant tissue and their place and purpose within a plant. Plant Tissue Definition Plant tissue is a collection of similar cells performing an organized function for the plant. Each plant tissue is specialized for a unique purpose, and can be combined with other tissues to create organs such as leaves, flowers, stems and roots. Plant Tissue Definition Plant tissue is a collection of similar cells performing an organized function for the plant. Each plant tissue is specialized for a unique purpose, and can be combined with other tissues to create organs such as leaves, flowers, stems and roots. The following is a brief outline of plant tissues, and their functions within the plant.  PLANT TISSUE Meristematic Permanent (Cells are capable of cell division) (Mature cells are incapable of cell division) Simple Complex (Tissue composed of single type of cells) (Tissue composed of more than one type of cell) Parenchyma Collenchyma Sclerenchyma Chlorenchyma Xylem Phloem -Xylem Vessels -Sieve Tubes -Tracheids -Companion Cells Types of Tissue in Plants MERISTEMATIC TISSUE MERISTEMATIC TISSUE Apical meristem is existent at the growing tips or apical of stems and roots. Apical meristem upsurges the length of the plant. Lateral meristem is existent in the radial portion of the stem or root. Lateral meristem upsurges the thickness of the plant. Intercalary meristem is found at the internodes or at the base of the leaves. Intercalary meristem upsurges the size of the internode. Old meristematic cells lose the capability to distribute and convert into permanent tissues. This procedure of capturing up a permanent function, size, and shape is termed as differentiation. and very small and few  ▪ Apical meristems contain ▪ Intercalary meristems occur only in meristematic tissue located at monocots at the bases of leaf the tips of stems and roots, blades and at nodes (the areas which enable a plant to extend in where leaves attach to a stem). length. This tissue enables the monocot leaf blade to increase in length from the leaf base; for example, it allows lawn grass leaves to elongate even after repeated mowing. ▪ Lateral meristems facilitate growth in thickness or girth in a maturing plant. ▪ Growth in plants is indeed restricted to specific regions known as meristems. These regions are responsible for the generation of new cells and tissues, allowing the plant to increase in size and develop various structures. The primary reason for this restriction is the need for precise control over where and how growth occurs, which is crucial for the plant's survival and adaptation. ▪ Focusing growth in specific areas allows the plant to conserve energy. Continuous growth throughout the entire plant would require a significant amount of resources and might not be sustainable. ▪ Controlled growth ensures that the plant maintains its structural integrity and can support its own weight. Without this control, the plant might become weak and unstable. ▪ Different regions of the plant have specialized functions, such as photosynthesis in leaves and nutrient absorption in roots. Limiting growth to specific regions allows the plant to allocate resources efficiently to meet these functions. ▪ When an apical meristem loses its ability to divide, it typically has significant consequences for the plant. The apical meristem is responsible for primary growth in plants, including the elongation of stems and the development of leaves, flowers, and other essential structures. ▪ when an apical meristem loses its ability to divide, it disrupts the plant's normal growth and development, leading to stunted growth, altered plant structure, and potential long-term consequences for the plant's ability to thrive and reproduce. The specific effects may vary depending on the extent of the damage and the plant species involved. ▪ The absence of vacuoles in meristematic tissue is a functional adaptation that supports rapid cell division which is essential for plant growth and development. Vacuoles become more prominent as the cells mature and take on their distinct roles within the plant. ▪ Plants can grow new roots and branches even if you trim their tips. This is called root branching or regeneration, and it happens because the plant receives signals from both its surroundings and its internal processes, which trigger the growth of new root structures. 4. Why is the absence of vacuoles observed in meristematic tissue? ✓ The absence of vacuoles in meristematic tissue is a functional adaptation that supports rapid cell division which is essential for plant growth and development. Vacuoles become more prominent as the cells mature and take on their distinct roles within the plant. PERMANENT TISSUE PERMANENT TISSUE These cells have lost their ability to distribute but are specialized to offer elasticity, flexibility and strength to the plant. These tissues can be additionally categorized into: Simple Permanent Tissue: They can be classified into sclerenchyma, collenchyma and parenchyma based on their purpose. Complex Permanent Tissue: These tissues include phloem and xylem. Xylem is valuable for the transportation of water and solvable constituents. It is made up of xylem parenchyma, fibers, vessels and tracheids. Phloem is valuable in the transportation of food particles. Phloem consists of phloem parenchyma, phloem fibers, companion cells, sieve cells and sieve tubes. PERMANENT (SIMPLE)  SIMPLE (Parenchyma, Collenchyma, Sclerenchyma) 1. Parenchyma Tissue: In plants, parenchyma is one of three types of ground tissue. Ground tissue is anything that is not vascular tissue or part of the dermis (skin) of the plant. In contrast to collenchyma and sclerenchyma cells, parenchyma cells primarily consists of all of the simple, thin walled, undifferentiated cells which form a large majority of many plant tissues. 1. Parenchyma Tissue: ▪ Parenchyma cells are notable for their thin walls, and for being alive at maturity. The parenchyma cells have thinner walls and stay alive at maturity. While this makes them less useful in structural applications, the cells can move and store water and nutrients as well as divide quickly. This is important for the growth and repair functions of the parenchyma cells. 1. Parenchyma Tissue: ▪ Each parenchyma cell may be a different shape, depending on its exact location and which tissue it is present in. However, it will always have a large central vacuole. This organelle is responsible for storing water and ions. This both creates a pressure between the parenchyma cells and their neighbors (called turgor pressure) and also allows the plant to store enormous amounts of water and nutrients. 1. Parenchyma Tissue: ▪ The thin walls of the parenchyma cells also allow the easy passage of sugars created in the leaves. ▪ The tissue referred to as "packaging tissue" in plants is often the parenchyma tissue. Parenchyma cells are known for their versatility and play multiple roles within plant organs. 1. Parenchyma Tissue: 2. Collenchyma Tissue: ▪ Collenchyma has thin walls with irregular thickness. They provide additional structural and mechanical support, especially around the new growing part of the plant. ▪ Their role is to provide structural support to the growing leaves and shoots. The cell walls, irregularly thick, are made of pectin and cellulose, and they are usually living cells. 2. Collenchyma Tissue: 3. Sclerenchyma Tissue: ▪ In-Plant, Sclerenchyma is the supportive Tissue, which is composed of various hard woody cells. Sclerenchyma cells once matured are usually the dead cells that have heavily thickened secondary walls containing lignin. These cells are found in the non-growing region of the Plants like bark and the mature stems, and these cells are rigid and non- stretchable in nature. Sclerenchyma is one of the three ground and fundamental Tissues found in the Plant. 3. Sclerenchyma Tissue: ▪ Sclerenchyma are composed of dead cells, which have thickened walls containing lignin and highly cellulose content from 60 - 80 percent. ▪ Some of the locations where Sclerenchyma is found are present in the stems around the vascular bundles, in the veins of the leaves, and the hard covering of the fruit, seed, and nuts. Coconut husk is also made up of the same kind of tissue. 3. Sclerenchyma Tissue: 3. Sclerenchyma Tissue: ▪ Sclerenchyma cells are mainly divided into two types Fibers and sclereids. Fibers ▪ They are greatly elongated cells having long and tapering ends which interlock to provide mechanical support to the Plant. Fibers usually occur in the bundles and they can be found almost everywhere on the plant body including the stem, roots, and vascular bundles of the leaves. 3. Sclerenchyma Tissue: Fibers ▪ Most of these Fibers include seed hairs, leaf Fibers, and bast Fibers, and these are an important source of the raw material for the textile industry and also for other oven goods. ▪ 3. Sclerenchyma Tissue: Sclereids ▪ They are defined as mechanical tissue having features like, they occur in a group or single, and they are found associated with the Plant vascular Tissue Xylem and phloem. The thickening of the cell wall in sclereids is non- uniform and it also contains a number of simple pits, with round apertures, and usually, the cells of the Sclerenchyma consist of the narrow lumen. 3. Sclerenchyma Tissue: Sclereids ▪ It is sometimes known as the stone cells and it is also responsible for the gritty texture of pears and guava.  Is Sclerenchyma also found in humans? Yes, only some of the Sclerenchyma cells are found in the human body, not all the cells. As humans mainly depend on the skeleton for support and flexibility and on complex organs to perform life functions. Why are intercellular spaces typically NOT found in sclerenchyma tissue? ▪ The absence of intercellular spaces in sclerenchyma tissue is a result of the specific structural and functional adaptations of these cells. Their thick, lignified secondary cell walls and role in providing mechanical support make the presence of intercellular spaces unnecessary for their function within the plant. ▪ Sclerenchyma cells are primarily associated with mechanical support and protection rather than functions like storage or gas exchange. As a result, they do not require intercellular spaces for the exchange of gases or the storage of materials like water or nutrients. Chlorenchyma Tissue: In leaves, they form the mesophyll and are responsible for photosynthesis and the exchange of gases, parenchyma cells in the mesophyll of leaves are specialized parenchyma cells called chlorenchyma cells (parenchyma cells with chloroplasts). Chlorenchyma Tissue: ▪ Chlorenchyma is a special type of Parenchyma tissue. ▪ It is special, because it contains chlorophyll- the green colored pigment that is responsible for photosynthesis. All cells in parenchyma have similar function as it is a simple permanent tissue, hence all cells in chlorenchyma , apart from filling bulk space, performs an additional task of photosynthesis. ▪ It is the mesophyll part of plant leaves and is also present in stems of some plants. Chlorenchyma Tissue: ▪ The main difference between meristematic and permanent tissues lies in their location, function, and cell characteristics. ▪ Meristematic tissues are typically found at these regions include the apical meristems (found at the tips of shoots and roots) and lateral meristems (found along the sides of stems and roots). ▪ Meristematic tissues are responsible for primary and secondary growth in plants. They are the sites of active cell division, giving rise to new cells that can differentiate into various specialized cell types. ▪ Cells in meristematic tissues are small, undifferentiated, and have thin cell walls. They have a high nucleus-to-cytoplasm ratio, indicating their active division. ▪ The main difference between meristematic and permanent tissues lies in their location, function, and cell characteristics. ▪ Permanent tissues are found throughout the plant, including in mature regions such as leaves, stems, roots, and reproductive organs. ▪ Permanent tissues serve various functions, including support, transport of water and nutrients, photosynthesis, and storage. They are composed of cells that have completed their growth and differentiation process. ▪ Cells in permanent tissues are differentiated and specialized for specific roles within the plant. For example, parenchyma cells are involved in photosynthesis and storage, while xylem and phloem cells are responsible for water and nutrient transport. PERMANENT (COMPLEX)  XYLEM (XylemVessles, Tracheids) Permanent Tissue: ▪ Complex permanent tissues are a collection of structurally different cells working together as a unit performing various complex functions. Thus, complex tissues consist of cells that are not of one type. ▪ Complex permanent tissues are also called vascular tissues because they help the transportation of water, minerals, and organic matter throughout the plant body. The two most common complex permanent tissues found in plants are Xylem and Phloem. XYLEM Xylem: ▪ Xylem is also known as wood tissue. Xylem tissues are responsible for the conduction of minerals and water from roots to leaves of the plant. It also provides physical support to the plants. Xylem tissues are made up of parenchyma cells, fibers, vessels, and tracheid cells. The tracheid and vessels are long, elongated, and hollow. PHLOEM Phloem: ▪ The phloem of the bust plant tissue is another type of vascular tissue found in plants. Its main function is the translocation of food from leaves to different plant parts. Phloem tissue consists of a sieve tube, companion cell, phloem fiber, and phloem parenchyma. Apart from the translocation of food, they are also responsible for the transportation of proteins and mRNAs throughout the plant body. Xylem and Phloem  Are plants and animals made of same tissues? Since animals are mobile, they require more Since plants are stationary, they do not require energy, hence more living tissues are required. much energy. Hence, more living tissues are not required. Animals move from one place to another in search In plants, most tissues provide structural strength. of food, shelter, etc. hence they need more energy Most of these tissues are dead and can provide and more tissues. mechanical strength as easily as the living ones and need less maintenance. Cell growth is uniformly distributed Growth is limited to certain regions Structural organization of organs and organ Comparatively less complex. systems is more specialized and complex. END