Supporting Tissues in Plants PDF

**[WEEK 5 NOTES]** C:\\Users\\SFFG\\Pictures\\IMG\_20241107\_064939 (1).jpg  **[SUPPORTING TISSUES IN PLANTS]** The knowledge of internal structure of stems, leaves and roots will assist in the understanding of the mechanis...

**[WEEK 5 NOTES]** C:\\Users\\SFFG\\Pictures\\IMG\_20241107\_064939 (1).jpg  **[SUPPORTING TISSUES IN PLANTS]** The knowledge of internal structure of stems, leaves and roots will assist in the understanding of the mechanism of support in plants. 1. **FUNCTIONS:** It protects the inner cells from injury and loss of water. 2. i. ii. iii. a. \(ii) They give flexibility or resilience to plants i.e enable plants to bend without breaking **(b)The Parenchyma tissues**: are found in the cortex of stem, phloem, root, leaf mesophyll and xylem. They are the most abundant of all plant tissues. **FUNCTIONS:** (I) They give support to plants, when the vacuoles are filled with cell sap.(ii) Parenchyma tissues give firmness and turgidity to the plants. (iii)Parenchyma cells contain chloroplast in the leaf mesophyll used for photosynthesis (iv)Presence of intercellular air spaces for gaseous exchange. (v)Parenchyma tissues store food and water. **(C)ENDODERMIS:** **FUNCTION:** They store starch hence when stained with iodine solution will turn black. **(3)SCLERENCHYMA:** These consist of dead lignified cells and are found on the outer part of the vascular bundle or vascular tissue. **FUNCTIONS:(i)** The sclerenchyma gives flexibility to plants (ii)They provide strength, rigidity, hardness and support to plant. **(4)VASCULAR BUNDLES OR VASCULAR TISSUES:** Found in the inner part of the stem or root. It consists of (i) **XYLEM**: conducts water and mineral salts from the soil to the leaves through the roots and stem. **(ii)PHOLEM:** is responsible for the conduction or transportation of manufactured food from the leaves to the area where they are needed. **(iii)CAMBIUM :**found between the phloem and xylem. **FUNCTION:** to produce cells which differentiate into more xylem and phloem tissues. **(IV)PITH:** is the central part of the dicotyledonous stem. **FUNCTION:** It provides rigidity in the stem. DIAGRAMS OF TS OF MONOCTYLEDONOUS OF STEM/ROOT AND TS OF DICOTYLEDONOUS STEM/ROOT. **[DIFFERENCES BETWEEN TRANSVERSE SECTIONS OF DICOTYLEDONOUS STEM AND MONOCOTYLEDONOUS STEM]** **DICOTYLEDONOUS STEM** **MONOCOTYLEDONOUS STEM** ------------------------------------------------------- ----------------------------- 1.Vascular bundles are arranged in rings in the stem. Vascular bundles scattered. **2.**Presence of pith. Absence of pith. **3.**Wide cortex in the stem Absence of cambium **4.**Fewer vascular bundles Many vascular bundles. **5.**Presence of cambium Absence of cambium **6.**Has distinct endodermis No endodermis. **[DIFFERENCES BETWEEN TRANSVERSE SECTIONS OF DICOTYLEDONOUS ROOT AND MONOCOTYLEDONOUS ROOT].** **DICOTYLEDONOUS ROOT** **MONOCOTYLEDONOUS ROOT** ----------------------------- --------------------------- 1.Fewer vascular bundles Many vascular bundles 2.The xylem is star shaped. Xylem is not star shaped. 3\. Pith is absent Pith is present. 4.Presence of cambium Absence of cambium. **[TYPES OF SUPPORTING TISSUES IN PLANT AND HOW THEY FUNCTION TO OFFER SUPPORT IN PLANTS]** Types of supporting tissues in plants are Parenchyma, Collenchyma, Scelerenchyma, Xylem tissues, Phloem fibres. C:\\Users\\Dell\\Pictures\\Diagram type of supporting tissues.jpg (1)**Parenchyma:** **(I)** Parenchyma tissues become turgid due to water in their large cell vacuoles filled with cell sap. This gives support to the plants. (ii)The rigid network of the cellulose cell wall also gives primary support to the plants. (2)**Collenchyma:** The tissue has thickened cell wall which offers rigidity and support to the plant **(3)The Sclerenchyma:** Sclerenchyma Cell walls are thickened with deposit of lignin which give rigidity and support to the plants. (4)**Xylem tissues:** is lignified to give strength and rigidity to plant parts. **[FEATURES OR STRUCTURE OF XYLEM TISSUE (IGCSE)]** -Long or tabular or lumen or hollow present. -Absence of end walls. -Dead cells or lack of cell contents. -Lignified walls. -Tracheids present. **[ADAPTIIVE FEATURES OF XYLEM TISSUES TO ITS FUNCTION (IGCSE)]** -Long tubular structure or no cytoplasm to transport water and mineral salts. -Dead elongated cells or lack cell contents such as cytoplasm and nucleus help to transport water and mineral salts. -Thick or strong or lignified cell walls for support -Lack of cross walls to transport water and mineral ions. **[FUNCTIONS OF XYLEM TISSUES]** 1. 2. 3. **[TYPES OF XYLEM TISSUES]** The xylem tissues are made up of the following cells which are Tracheids, vessels, fibres, xylem parenchyma. i. ii. iii. iv. (i)**Sieve tubes:** are elongated rows of cylindrical cells vertically arranged, living and they conduct mainly food. (ii)**Phloem Parenchyma**: are similar to the parenchyma cells. They provide strength and support to the plant. They also help in food storage 1. 2. 3. 1. 2. 3. 4. 5.