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Structure of the root

Structure of the root<br>Types of root system<br>Metamorphosis of the root<br><br>

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Structure of the root

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  1. RootsRoots have many functions. 1. anchor the plant 2. bind soil… stops erosion 3. absorb water and minerals 4. store food (usually as starch)

  2. Root Types

  3. Taproots • look large and fleshy, • are mostly found in plants with two seed-leaves (dicots), • grow deep into the ground to search for food, • are able to store food, which is particularly necessary for perennial plants during periods of dormancy.

  4. Fibrous roots • lie close to the surface of the soil, • are mostly found in plants with one seed-leaf (monocots) • collect precipitation before it sinks deep into the ground, • can often be found growing side by side with taproots- the two types of roots combine efforts to maximize efficiency.

  5. Adventitious roots • are common in both dicots and monocots • develop to help the plant climb: for example, ivy • help develop modified underground stems, such as bulbs

  6. Aerial Rootsmodified to absorb water from the air Aerial roots of an Orchid Orchids in bloom

  7. Root Hairsare actually epidermal cells adapted to absorb water Root Hairs * Water enters the cells by Osmosis * Minerals enter by Active Transport

  8. Regions of the root tip • Region of Maturation - Most cells differentiate into various distinctive cell types. • Root hairs form. • Region of Elongation - Cells become several times their original length. • Vacuoles merge • Region of Cell Division - Composed of apical meristem in the center of the root tip. • Most cell division occurs at the edge of the inverted cup-shaped zone. • Root Cap - Thimble-shaped mass of parenchyma cells covering each root tip. • Protects tissue from damage. • Function in gravity perception.

  9. The Root Tip

  10. The Function of Root Tissues • Epidermis – outer layer of cells, provide protection from drying out, water loss and infection. • Cortex– area made up of parenchymacells. Parenchyma cells are usually storage cells • Endodermis – regulates materials entering the center of the root. • Pericycle –the outermost layer of cells of the stele • Xylem – transports water • Phloem – transports sugar • Stele – Also known as the “Vascular Cylinder”…… made up of the xylem and phloem • Pith – tissue located in the center of the stem • Apical Meristem - (Meristematic Tissue) – tissue that in a constant state of growth… apical means “located at the tip” • Meristemaccounts for the increase in length of the roots and stems.

  11. Dicot Root X-section

  12. Monocot root X-section

  13. Dicot root X-sectionMostDicot roots have an “X” of xylem cells in the center of the root.

  14. The Casparian Stripregulates the movement of water into the root

  15. Stele

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