Plant Body (Chapter 33) - Cell Tissues & Growth
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Uploaded by SpellboundChrysoberyl
American University of Sharjah
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This document presents an overview of plant biology, covering plant cells, various types of plant tissues such as dermal, ground, and vascular, the processes of primary and secondary growth, and the structures involved. It offers insights into plant organization and the functions of different tissues and cells.
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BIO 102 CHAPTER 33: PLANT BODY Plant cells Plant cells have: Chloroplasts for photosynthesis. Large Vacuoles to maintain cell’s turgid pressure, and store useful minerals and nutrients, among other functions. Cell walls with cellulose to provide structural support. Plasmo...
BIO 102 CHAPTER 33: PLANT BODY Plant cells Plant cells have: Chloroplasts for photosynthesis. Large Vacuoles to maintain cell’s turgid pressure, and store useful minerals and nutrients, among other functions. Cell walls with cellulose to provide structural support. Plasmodesmata to connect adjacent plant cells. Plant tissues There are 3 general types of plant tissues: 1. The dermal tissue consist in epidermis and periderm. * Epidermis: Closely packed cells that cover and protect the tissues beneath and control water loss. Can secrete cuticle, waxy substance that protects from water loss and pathogens. Can have hair-like structures and stomata with guard cells (dry areas) to help CO2/H2O exchange: https://www.britannica.com/video/21899/ Microphotography-animation-stomate-fun ction Plant tissues The periderm is the thick layer of dead cells that grows on the outside of stems and roots, due to secondary growth. * it is part of the bark. The periderm protects the plant from pathogens, injury, and excessive water loss. Plant tissues 2. The ground tissue makes up the majority of the plant. This tissue is composed of parenchyma, collenchyma, and sclerenchyma cells. * parenchyma cells are the most common and do many jobs: - photosynthesize (gas exchange/create sugars). - store energy as starch (polysaccharide). * collenchyma and sclerenchyma cells give strong, flexible structure. - have thick cell cellulose/lignin walls Plant tissues 3. The vascular tissue The xylem: Tracheids and vessel elements. Cells with wider diameter, that transport materials more efficiently, and allow faster growth in angiosperms. The phloem: Sieve tube cells are supported by companion cells in angiosperms, which facilitate efficient nutrient transport. Growth in plants The primary growth in a plant is upwards (shoot system; in the air) and downward (root system; underground). This growth is done by apical meristems, with cells that copy/reproduce themselves continuously. - The root apical meristem has a cap to push trough the soil to find water. New cells get longer, mature, and push the cap to the tip (“downwards”). - The shoot apical meristem: lacks a cap. Produces new cells behind it and grows up. Secondary Growth Secondary growth is an outward growth where stems and roots get thicker over time (wooded growth). Secondary growth is formed by the vascular cambium, a thin layer of cells located between the xylem and phloem. These cells create new xylem to the interior, which pushes the vascular cambium outwards (away from the center). These cells also create new phloem to the exterior, that pushes the old phloem outwards.
