Part 1| Tissues : All Plant Tissues Class 9th Science | Chapter 6 Tissues class 9 science NCERT
Class 8/9 Science by Armaan・54 minutes read
Plant tissues consist of meristematic tissue for growth and permanent tissue for specific functions, including parenchyma, collenchyma, and sclerenchyma. The epidermis protects against water loss, while cork serves as a protective barrier composed of suberin and fatty acids, forming dead cells with zero intercellular space.
Insights
- Tissues are groups of cells with similar functions, including meristematic tissues that continuously divide and eventually differentiate into permanent tissues. Permanent tissues, such as parenchyma, collenchyma, and sclerenchyma, have distinct structures and functions in plants, contributing to flexibility, support, and storage.
- The epidermis, a protective layer in plants, plays a crucial role in resisting water loss, mechanical injury, and pathogen invasion. Specialized structures like stomata and cuticle regulate gas exchange and water absorption, while cork, formed by secondary meristems, provides impermeability and protection against external factors, emphasizing the intricate defense mechanisms in plant tissues.
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Recent questions
What are the two main types of plant tissues?
Meristematic and permanent tissues.
What are the three types of meristematic tissues in plants?
Apical, intercalary, and lateral meristems.
What are the characteristics of sclerenchyma tissues?
Dead cells, thick lignified walls, mechanical support.
What is the function of the epidermis in plants?
Outer protective layer, water resistance, gas exchange.
What are the functions of xylem and phloem tissues in plants?
Transport water, minerals, food, and hormones.
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Summary
00:00
Biology: Tissues and Their Functions
- Chapter two of class ninth biology is about Tissues, following the Cell chapter in the Unit of Life.
- Tissues are groups of similar cells performing specific functions.
- Plant tissues include meristematic tissue and permanent tissue.
- Meristematic tissue continuously divides and eventually stops dividing.
- Meristematic tissue cells are undifferentiated, actively dividing, with thin cell walls, dense cytoplasm, and large nuclei.
- Permanent tissue is formed from meristematic tissue and consists of differentiated cells with larger size and less dense cytoplasm.
- Meristematic tissue is classified into apical, intercalary, and lateral meristems based on location.
- Apical meristem is found on growing tips of roots and shoots, aiding in lengthening.
- Intercalary meristem is located between nodes, increasing internode length.
- Lateral meristem is present on the lateral side of stems and roots, increasing thickness or girth.
11:30
Meristems and Permanent Tissues in Plants
- Meristems increase thickness in specific areas: near stem, lateral meristem increases stem girth, near root meristem increases root thickness.
- Lateral meristem, also known as cambium, crucial for stem and root thickness.
- Three meristems in plant structure: apical, intercalary, lateral.
- Permanent tissues follow meristematic tissue conversion: simple and complex permanent tissues.
- Simple permanent tissues include parenchyma, collenchyma, sclerenchyma.
- Parenchyma: unspecialized cells, loosely arranged, thin cell walls, storage of food, chlorophyll presence leads to chlorenchyma.
- Collenchyma: elongated cells with thickened corners, provides flexibility and mechanical support.
- Collenchyma present in tendrils, stems, branches for flexibility.
- Sclerenchyma: dead cells with thick, lignified cell walls, long and narrow shape, absent intercellular space, provides mechanical support and strength.
- Sclerenchyma present in leaves and near vascular bundles in mature stems, forms hard coverings in leaves, seeds, and nuts.
23:06
Plant Epidermis: Structure, Function, and Protection
- The outer covering of a nut is made from the slane of the coconut, which is also composed of Sclean Kaama.
- The transverse section of a nut shows its structure, with the longitudinal and transversal cuts revealing different aspects.
- The epidermis in plants is the outermost protective layer, made up of a single layer of cells and present on plant parts exposed to air.
- The epidermis is thicker in plants living in dry habitats, secreting a waxy layer that resists water and protects against water loss and mechanical injury.
- The epidermis protects against parasitic fungi and lacks intercellular space, with flat-shaped cells arranged in a single layer.
- The outer side of epiderm cells is thicker than the inner side, with stomata present in the epidermis for gas exchange and water regulation.
- Stomata are formed by guard cells surrounded by epiderm cells, opening and closing to regulate gas exchange and water loss.
- Epiderm cells in roots form long hair structures for water absorption, while cuton, a water-resistant wax, is secreted by epiderm cells in desert plants.
- Cuton is composed of fatty acids, providing a waterproof covering, while suberin in cork cell walls prevents water and gas passage and protects against pathogens.
- Cork is a protective tissue that forms as a plant grows, containing suberin in its cell walls for protection and impermeability.
34:28
"Cork: Protective Layer in Plant Cells"
- Cork is the outer layer of a plant that provides protection.
- Cybin is present in the cell wall of cork cells and acts as a barrier against pathogens.
- Suberin in cork cells protects plants from mechanical stress.
- Cork is composed of fatty acids and suberin, found in all plants with cork.
- Suberin is secreted by epidermal cells and deposited between cork cells.
- Cork is made of dead cells and serves as protective tissue.
- Secondary meristem in the cortex region of plants forms cork.
- Cork cells have zero intercellular space and are tightly packed.
- Xylem and phloem are complex tissues that transport water and minerals in plants.
- Xylem fibers provide mechanical strength, while xylem parenchyma stores food.
47:18
Phloem: Transporting food and hormones efficiently.
- Phloem is composed of sieve tubes which are tubular structures with perforated walls.
- Sieve tubes are responsible for transporting food, mainly sucrose, with the help of sieve plates.
- Sieve tubes are formed by sieve cells, which lack a nucleus and have a short lifespan.
- Phloem fibers provide mechanical support, while phloem parenchyma stores food and allows photosynthesis.
- Companion cells are essential for controlling sieve tubes, aiding in loading and unloading sugars for transportation.
- Phloem not only transports food but also hormones, with xylem parenchyma being the only truly living component in the complex tissue.
