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Summary IB Biology Topic 9: Plant Biology £4.44   Add to cart
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  3. International Baccalaureate Diploma
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  5. Biology SL and HL

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Summary IB Biology Topic 9: Plant Biology
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  • Module
  • Biology SL and HL
  • Institution
  • International Baccalaureate Diploma
  • Book
  • IB Biology Course Book

Detailed objective-by-objective summary notes for Topic 9: Plant Biology for IB Biology HL. Contains information on everything you need to know from 9.1 to 9.4, according to each understanding, application or skill. Written by a IB HL Biology student who graduated with a 45/45.

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  • Unknown
  • March 5, 2019
  • 8
  • 2016/2017
  • Summary

Subjects

  • ib biology
  • biology
  • science
  • plant
  • xylem
  • phloem
  • meristem
  • auxin
  • international baccalaureate
  • hl
  • sl
  • ib

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  • International Baccalaureate Diploma
  • Biology SL and HL
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IB TOPIC 9 | PLANT BIOLOGY
2016 | SYJ0014


Topic 9.1: Plant biology – Transport in the xylem of plants
Structure and function are correlated in the xylem of plants.

• Understanding: Transpiration is the inevitable consequence of gas exchange in the leaf.

 Stomata: pores in the epidermis of a leaf that allows for gas exchange
 Guard cells: cells found in pairs on each side of a stoma that can control the opening of the stoma
 Absisic acids: hormones that control the opening and closing of the stoma by stimulating guard cells

 Transpiration: loss of water vapour from the leaves and stems of plants
 When plants absorb carbon dioxide and excrete oxygen during photosynthesis, water vapour also can escape
 Water evaporates out due to a water potential gradient inside and outside of the plant
 Therefore, transpiration is the inevitable consequence of gas exchange
 Water is lost from the spongy mesophyll cells through stomata to the atmosphere

• Understanding: Plants transport water from the roots to the leaves to replace losses from transpiration.

 Movement of water from roots to leaves:
 Stoma: water is lost from stoma due to concentration gradient
 Leaf: water leaving stoma is replaced from xylem
 Xylem: water in xylem climbs stems due to low concentration gradient in the
leaf (transpiration pull)
 Root: water moves into soil into roots by osmosis, and water in root replace the
water in xylem that is released

 Pathway for water absorption in root:
 Apoplast: water is absorbed through the cell wall (red)
 Symplast: water is absorbed through cytoplasm

• Understanding: The cohesive property of water and the structure of the xylem vessels allow transport under tension.

 Plants and cohesive property of water:
 Cohesion property of water: water has strong cohesive property as they attract each other strongly with hydrogen bonding
 Application in plants: plant utilizes the strong cohesion property to pull up water in a continuous stream through various structure
 Long continuous tube: adjacent cell wall area is broken down to maximize transport of water
 Thickened wall: cellulose and lignin harden the xylem wall so cells can withstand low pressure

• Understanding: The adhesive property of water and evaporation generate tension forces in leaf cell walls.

 Plants and adhesive property of water:
 Adhesive property of water: water molecules are polar and thus are attracted to other polar molecule
 Application in plants: plant utilizes the adhesive property to pull up water in a continuous stream against gravity
 Transpiration pull forms: evaporation from the leaf to the atmosphere causes a transpiration pull
 Tension force forms: tension force is generated as the low water potential in the leaf pull the water from the root
 Water pull: force of adhesion alongside others allows xylem to pull up water against gravity

• Understanding: Active uptake of mineral ions in the roots causes absorption of water by osmosis.

 Active uptake of mineral ions in the root:
 Solute concentration difference: solute concentration inside the root is greater than that in the soil
 Active transport: to maintain concentration of mineral ions, the difference is established via active transport
 Use of ATP: ATP is consumed during active transport
 Mitochondria abundance: root epidermal cells are rich in mitochondria and requires oxygen
 Diffusion: water diffuses into the root by osmosis

 Characteristics of root for absorption:
 Branched roots: roots are branched to increase surface
 Root hairs: extensions of epidermis that increase surface area
 Multiple different pathway: different methods of the water can travel through
 Mutualistic relationship: plants build relationship with fungus that absorb mineral ions that is supplied to the root

• Application: Models of water transport in xylem using simple apparatus including blotting or filter paper, porous pots and capillary tubing.

 Porous pots:
 Target of experiment: modelling transpiration pull; cohesion and adhesion property of water
 Situation: water evaporates out form the surface of the porous pots
 Explanation: water is drawn up from glass tubing and is lost from trough as there is a transpiration pull

 Capillary tubing:
 Target of experiment: modelling cohesion and adhesion property of water and other liquids
 Situation: capillary tube is dipped into water with dye and mercury
 Capillary tube in water: dyed water climb up the tube due to adhesion and cohesion of water
 Capillary tube in mercury: mercury does not climb up the tube due to lack of both adhesion and cohesion
 Explanation: water has stronger adhesion and cohesion property due to its polar nature and intermolecular hydrogen bonding




LAST EDITED 2017-03-17 | 1

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