Plant biology - Growth

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Plant biology - Growth

  1. 1. Primary & Secondary Growth Apical & Lateral MeristemPlant Biology Part 3 - Growth
  2. 2. Type of Growth Primary growth: grow in length Secondary or lateral growth: grow in girth (diameter, width)
  3. 3. Primary Growth Increase height for better clearance to sunlight Roots burrow deep into soil to access nutrients and for structural stability Occurs in:  Herbaceous plants  Young plants  Tips of roots and shoots of woody plants
  4. 4. Meristematic Cells (Meristem) Undifferentiated plant cells 2 types:  Apical  Lateral
  5. 5. Apical Meristem Undifferentiated cells at the tips of plant roots and shoots (buds) Cells that divide enable the plant to grow longer (deeper into the ground, and taller)
  6. 6. Root ApicalMeristem
  7. 7. Root Zones  Zone of maturation: cells differentiate into different types of cells  Zone of elongation: allows the root to get deeper within the soil  Meristematic region: rapid mitosis of undifferentiated meristematic cells  Root cap: protects the meristematic region
  8. 8. Shoot Apical Meristem Located in buds Terminal / Terminal / Apical Apical bud bud: at the tip of a Axillary / growing stem Lateral bud Axillary / Lateral bud: at points along the stem where lateral branches form
  9. 9. Shoot Apical Meristemhttp://www.fs.fed.us/pnw/olympia/silv/local-resources/glossary/images/apical.jpg http://www.uwgb.edu/biodiversity/herbarium/trees/axillary_lateral_bud02.jpg
  10. 10. Apical Dominance Terminal bud inhibits the growth of axillary bud What advantage does this provide for the plant?
  11. 11. Apical Dominance What would happen to plant growth if the terminal bud was cut off? Explain why pruning shrubs makes them busier.
  12. 12. Apical Dominance http://www.mun.ca/biology/desmid/brian/BIOL3530/DB_12/fig12_13.jpg
  13. 13. Secondary / Lateral Growth Thickening of roots and shoots Adds strength to plant structure Growth due to lateral meristem Never occurs in leaves Occurs in mature part of woody plants
  14. 14. Secondary Growth Accounts for the rings formed in tree trunks
  15. 15. http://www.uic.edu/classes/bios/bios100/labs/vasccamb.jpg
  16. 16. Lateral Meristem Cork Cambium  Outer lateral meristem  Makes dermal tissue called cork / periderm  bark Vascular Cambium  Inner lateral meristem  Outer surface makes phloem  bark  Inner surface makes xylem  reason for growth, creates the tree rings seen in trunks of woody plants
  17. 17. Comparing Plant GrowthGrowth Effect MeristemPrimary Height Root Apical meristem deep roots Shoot Apical meristem apical/terminal bud axillary/lateral budSecondary / Width / girth Lateral meristemLateral Cork cambium Vascular cambium

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