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Roots Postlab


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Post lab lecture on root anatomy

Roots Postlab

  1. 1. ROOT ANATOMY<br />Post lab discussion<br />
  2. 2. shoot apical meristem<br />terminal bud<br />leaf<br />axillary bud<br />blade<br />vascular tissue<br />petiole<br />node<br />Shoot <br />system<br />internode<br />vascular tissue<br />vascular tissue<br />Root<br /> system<br />Lateral roots<br />dermal tissue<br />root apical meristem<br />ground tissue<br />root cap<br />root tip<br />vascular tissue<br />
  3. 3. protoderm<br />ground meristem<br />procambium<br />Root<br />Elongation region<br />tip<br />Meristematic region<br />Actively dividing cells <br />in various stages of mitosis<br />Root cap<br />Produces mucigel for<br />protection, lubrication,<br />water and nutrient absorption<br />
  4. 4. Maturation region<br />Maturation region<br />- characterized by the presence of root hairs<br />- is made up of primary tissues that develop<br /> from transitional meristems <br /> of the elongation region<br />epidermis<br />Protoderm<br />cortex<br />Ground meristem<br />pericycle<br />phloem<br />Procambium<br />vascular cambium<br />xylem<br />
  5. 5. ROOT HAIRS<br />-Increase the surface area<br /> for the absorption of water<br />- trichoblast<br />
  6. 6. ROOTS vs STEM<br />STEM<br />Endarch<br />with appendages<br />With stomata<br />Branches arise from apical merisetm and EXOGENOUSLY<br />ROOT<br />Exarch<br />No appendages comparable to leaves<br />Devoid of stomata<br />Braches arise from mature tissue and ENDOGENOUSLY<br />
  7. 7. ROOT vs Stem<br />Root wider cortex<br />Roots have no or lesser supporting tissues. WHY?<br />Roots protosteleic; stem siphonostelic<br />
  8. 8. Roots vs STEM<br />Roots– x and p arranged alternately<br />Stem– in bundles<br />
  9. 9. Internal structure<br />Root cap<br />Epidermis<br />Cortex– parenchymatous (dicot and gymno); + sclerenchym (monocot)<br />EXODERMIS/ Hypodermis- suberized/ protective<br />ENDODERMIS- prevents inward flow of water and nutrients via apoplast<br />- uniseriate<br />- shed together with cortex during 2 growth<br />Vascular cylinder – surrounded by pericycle---<br />
  10. 10. lateral root arising from<br />pericycle<br />Anatomy of a young dicot root<br />xylem<br />phloem<br />endodermis with <br />casparian strip<br />cortical parenchyma<br />uncutinized epidermis with<br />root hair<br />
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  13. 13. cortical parenchyma<br />endodermis<br />xylem of <br />vascular cylinder<br />Casparian strip<br />H20<br />Endodermis<br />(surface and side views)<br />
  14. 14. primary root<br />xylem<br />lateral root<br />Lateral roots <br />develop from<br /> the pericycle<br />
  15. 15. Pericycle<br />&gt;uniseriate in most angio<br />&gt;several layers in monocot and gymno<br />&gt;Gives rise to <br />Lateral roots<br />Phellogen<br />Portion of vascular cambium<br />&gt;procambiumor ground meristemorigin<br />
  16. 16. epidermis<br />cortex<br />vascular cylinder<br />Young dicot root<br />actinostele<br />tetrarch<br />exarch<br />
  17. 17. Differentiating<br />metaxylem at the <br />centre of the root<br />The Dicotyledonous root<br />Young dicot roots usually have two, three four or morePOLES<br />of XYLEM which are interspersed<br />with STRANDS OF PHLOEM<br />MX<br />
  18. 18. metaxylem <br />vessel<br />protoxylem<br />vessel<br />Monocot root<br />actinostele<br />polyarch<br />exarch<br />exarch<br />
  19. 19. Parenchymatous central pith<br />Large number of xylem strands<br />PX exarch, MX endarch. <br />thick‑walled <br />endodermal cells<br />Cortex: Wide and parenchymatous<br />hypodermis the outer walls <br />of which are not thickened<br />epidermis<br />Zea mays root<br />
  20. 20. PASSAGE CELLS allow transport of water<br />Phloem occurs as STRANDS.<br />Alternates with protoxylem<br />Central core contains tracheids<br />endodermis<br />MX<br />Protoxylem is exarch<br />Metaxylem is endarch<br />
  21. 21. ENDODERMIS<br /><ul><li>The endodermis here has</li></ul>Thickenings as evidenced by the red Stained portions. <br />But not all portions have thickened cell walls (encircled). These are called PASSAGE CELLS and are located opposite the xylem poles. The next tissue layer to the endodermis is the pericycle which gives rise to lateral roots.<br />phloem<br />xylem<br />xylem<br />xylem<br />phloem<br />phloem<br />xylem<br />phloem<br />
  22. 22. Secondary growth in roots<br />Monocots do not exhibit secondary thickening<br />
  23. 23. Roots which have undergone<br />Secondary growth are shown below<br />Primary xylem<br />The structure of the root in<br />Secondary growth is similar<br />With the structure of stem in secondary except for the absence of pith in roots.<br />Secondary xylem<br />Primary xylem<br />
  24. 24. This is a cross section of the<br />Stem with secondary growth.<br />Take note of the presence of<br />pith<br />
  25. 25. Older roots– for conduction, storage, anchorage<br />Feeder roots– of primary state– for absorption<br />ROOTS vs STEM (secondary growth)<br />Roots have:<br />1. higher bark to wood ratio<br />2. less fibers in the bark and wood<br />3. larger and uniform vessels<br />4. less distinct growth increment<br />5. large volume of ray tissue<br />6. wider and longer tracheids (gymno)<br />7. large volume of living cells<br />