Phloem Tissue and types of cell found in phloem.pptx

Phloem tissue and its strucute types of tissues found in phloem

1. IN THE NAME OF ALLAH , THE MOST MERCIFUL THE MOST GRACIOUS

2. Wednesday, February 12, 2025 Phloem Tissue

3. 1. Xylem 2. Phloem Function Function Transport water Transport minerals Transport food Wednesday, February 12, 2025 Vascular Tissue

4. How do plants transport materials to where they are needed? Wednesday, February 12, 2025 Vascular Tissue

5. Phloem is a complex tissue that serves as the transportation system for soluble organic molecules in vascular plants. The phloem, composed of living tissue, actively transports sugars to plant organs such as the fruits, flowers, buds, and roots using turgor pressure and energy in the form of ATP. This movement process is called translocation. The term phloem, derived from the Ancient Greek word phloiós meaning “bark,” is the innermost layer of the bark in trees. The term was coined by Carl Nägeli in 1858. What is Phloem? Wednesday, February 12, 2025

6. Phloem transports water and dissolved carbohydrates (primarily sugars) from the leaves to other parts of the plant. Phloem cells are called sieve tube cells because they have sieve plates at each end. Phloem cells are parenchyma cells that remain alive At maturity, sieve tube members contain no nuclei. The cytoplasm of each sieve cell is connected by pores to a small nucleated companion cell next to it. The companion cell appears to direct the operation of the sieve cell If the companion cell dies, the sieve cell stops functioning. Cytohistological characters of meristematic tissue Wednesday, February 12, 2025

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8. The phloem structure is made up of three types of cells: conducting cells, parenchyma cells, and supporting cells. The conducting cells, also known as sieve elements, are made up of rows of sieve tube cells with holes in their lateral walls. These holes facilitate the movement of nutrients throughout the plant . The parenchyma consists of two specialised cells, companion cells, albuminous cells, and unspecialised cells used for storage. The companion cells, as their name suggests, work alongside the sieve tube cells to support the metabolic processes of the sieve components.  Plasmodesmata  connect the companion cells to the components of the sieve tube. The supportive cells are sclerenchymatous cells, specifically fibres and sclereids . They mainly serve supportive and mechanical purposes. The secondary cell walls of both cells give them rigidity and high tensile strength. The structure of the phloem is composed of various components. Each component functions together to enhance the transfer of carbohydrates and amino acids from a source to sink tissues, where they are utilised or stored. Most of the cells in phloem sieve tubes are made up of sieve element cells and companion cells. Sclerenchyma and parenchyma cells are also found in the phloem, filling in extra gaps and providing support. Structure of Phloem Tissue Wednesday, February 12, 2025

9. Wednesday, February 12, 2025 Structure of Phloem Tissue

10. The Sieve Elements Sieve elements are the most highly specialised plant cell type. They are unique in that they lack a nucleus at maturity and other organelles, including cytosol, ribosomes, and Golgi apparatus. This maximises the amount of space that can be used for material translocation. The elongated, narrow cells that make up the sieve elements are connected to form the phloem’s sieve tube structure . The two primary forms of sieve elements are the ‘sieve member,’ found in angiosperms, and the more primitive ‘sieve cells,’ which are associated with gymnosperms. Both are derived from a common type of “mother cell ”. Sieve Plates Sieve plates, modified plasmodesmata , are found at the junctions between sieve member cells. Sieve plates are comparatively large, thin sections of pores that make it easier for materials to move between element cells . Sieve plates also serve as a barrier to stop sap loss when the phloem is cut or harmed, which is frequently done by an insect or herbivore . Gymnosperms contain more primitive sieve elements than angiosperms do. Instead of sieve plates at the tapering end of the cell walls, they have numerous pores that allow material to pass through freely. Structure of Phloem Tissue Wednesday, February 12, 2025

11. The Companion Cells: Each sieve element cell generally has a “companion cell” in angiosperms and an albuminous cell (“ Strasburger cell”) in gymnosperms . Companion cells possess a nucleus, a thick cytoplasm, a large number of ribosomes, and a large number of mitochondria. This indicates that because the sieve element lacks the necessary organelles, the companion cells can carry out the metabolic processes and other cellular tasks . Thus, companion cells are responsible for supplying energy for the movement of materials throughout the plant and the sink tissues, and for the facilitation of loading sieve tubes with photosynthesis-related products and unloading at the sink tissues . Phloem Parenchyma A group of cells called the parenchyma serves as the “filler” in plant tissues. They contain cellulose walls that are thin but flexible. Starch, lipids, proteins, tannins and resins in some plants are primarily stored by the parenchyma within the phloem . Phloem Sclerenchyma Phloem fibres contain sclerenchymatous cells. The sclerenchyma mainly supports the phloem, giving the plant stiffness and strength. Both fibres and sclereids , two types of sclerenchyma, have a strong secondary cell wall and are often dead when they reach maturity . Structure of Phloem Tissue Wednesday, February 12, 2025

12. Nucleus controls activities of both companion and sieve tube cell Phloem Structure Sieve plates Mature cells have no nucleus Cytoplasm extends from cell to cell through the sieve plate 2 Companion Cells 1 . Sieve tube Members Wednesday, February 12, 2025

13. Wednesday, February 12, 2025 Structure of Phloem Tissue

14. Longitudinal and Transverse sections Wednesday, February 12, 2025 Structure of Phloem Tissue

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16. Wednesday, February 12, 2025 Phloem Classification

17. Wednesday, February 12, 2025 Types of Phloem S.No Primary Phloem Secondary Phloem 1 It is made up of the apical meristem's procambium . The lateral meristem, also known as the vascular cambium, produces secondary xylem. 2 It is found in the main plant body of all vascular plants. Except for annuals, it is only found during secondary growth of dicots and gymnosperms. 3 Every organ contains primary phloem. Secondary phloem is only found in the stems and roots of perennial dicots and gymnosperms. 4 It's on the margins of plant bodies. It grows within the primary phloem. 5 A radial system is not in place. Radial system is traversed by the radial system of phloem rays. 6 Phloem fibres are scarce. Phloem fibres are exclusively present in the plant's peripheral regions. 7 The phloem fibres are more abundant. There are often patches or bands of phloem fibres . 8 The cell types in the main phloem are distributed unevenly. The secondary phloem arrangement is more uniform. 9 There are few sieve tubes in it. It contains more sieve tubes. 10 Sieve tubes are thick and long. Sieve tubes are thicker and shorter in length. 11 There is a scarcity of phloem parenchyma. It contains a lot of phloem parenchyma.

18. Wednesday, February 12, 2025 Primary and Secondary Phloem

19. Wednesday, February 12, 2025 Types of Phloem S.No Character Protophloem Metaphloem 1 Definition Protophloems are the first structures that are produced as a result of primary growth in the phloem. Metaphloems are formed after the formation of protophloem . 2 Growth It is formed even before the maturation of plant organs. It is formed after the maturation of plant organs. 3 Composition It is composed of sieve tubes, phloem fibres and phloem parenchyma. It is composed of sieve tubes, phloem fibres , companion cells and phloem parenchyma. 4 Companion Cells Companion cells are absent. Companion cells are present. 5 Size of Cells The protophloems have smaller cells and are therefore less prominent structures. They have bigger cells and are more prominent structures. 6 Sieve Elements The sieve elements are narrow and thin The sieve elements are wide and long. 7 Life They are short-lived and get crushed in the later stages of growth. They are longer living than protophloem but may get crushed during secondary growth. 8 Stretchability The cells are more stretchable. The cells are less stretchable.

20. Wednesday, February 12, 2025 Primary and Secondary Phloem

21. Wednesday, February 12, 2025 What is transported in phloem?

22. The mechanism of phloem transport The Pressure-Flow Model Wednesday, February 12, 2025

23. Sources and sinks Direction of transport through phloem is determined by relative locations of areas of supply, sources and areas where utilization of photosynthate takes place, sinks. Source: any transporting organ capable of mobilizing organic compounds or producing photosynthate in excess of its own needs, e.g., mature leaf, storage organ during exporting phase of development. Sink: non photosynthetic organs and organs that do not produce enough photoassimilate to meet their own requiements , e.g., roots, tubers, develpoping fruits, immature leaves. Photosynthesis provides a sugar source New growth is a sugar sink Translocation Wednesday, February 12, 2025

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25. General diagram of translocation Physiological process of loading sucrose into the phloem Physiological process of unloading sucrose from the phloem into the sink Pressure-flow Phloem and xylem are coupled in an osmotic system that transports sucrose and circulates water. Wednesday, February 12, 2025

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27. Transports food Phloem carries food produced by photosynthesis from the leaves to other parts of the plant. This includes sugars, amino acids, and other nutrients.  Supports growth Phloem transports food to growing parts of the plant, such as roots, flowers, and fruits.  Coordinates plant response Phloem transports signaling molecules that help the plant respond to internal and external stimuli.  Stores food Phloem transports food to parts of the plant where it's stored as reserve compounds.  Functions of Phloem Tissue Wednesday, February 12, 2025

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29. Thank you Wednesday, February 12, 2025