8: Transport in plants Flashcards

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1
Q

Vascular Bundle

Xylem & Phloem
what it transports, process, direction of flow, cells

A

xylem + phloem
transport system - has thick cell walls to support the stem and leaf

XYLEM
1. transports WATER, MINERALS by TRANSPIRATION
2. ONE way direction of flow (roots ➝ leaves)
3. Cells - dead
Adaptation: - hollow, dead cells (lose their organelle, cytoplasm) - join in continuous flow of water
- lignin strengthens

PHLOEM

  1. transports SUCROSE (glucose + fructose), AMINO ACIDS by TRANSLOCATION
  2. BOTH directions
  3. Cells - living
  4. no nucleus
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2
Q

Position of xylem and phloem in a leaf, stem and root

A

Leaf: Xylem always on top of phloem

Stem: xylem inside of stem; phloem outside

Root: xylem in the middle in an X shape; phloem outside

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3
Q

Pathway of water

A

Root hair cell (osmosis) ➝ root cortex cells ➝ xylem ➝ diffuses into mesophyll cells ➝ used in metabolic reactions

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4
Q

Root Hair Cell adaptation

A

Long root hair extensions = large surface area of root hairs

  • increases the rate of the absorption of
  • water by osmosis and
  • ions by active transport
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5
Q

Define Transpiration

A
  • LOSS OF WATER VAPOUR
  • from plant leaves by evaporation of water
  • at the surfaces of the MESOPHYLL cells
  • followed by DIFFUSION of WATER VAPOUR through the STOMATA
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6
Q

Explain the effects of variation of temperature and humidity on transpiration rate

A

higher temp = faster

higher humidity = slower - concentration gradient of water vapour inside is low - diffusion out of plant is slower

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7
Q

Explain how and why wilting occurs

A

Lack of water

water moves out of cells, turgor pressure decreases, strength of cell wall decreases = cannot support plant.

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8
Q

Why is water lost from plants?

A

Plants have

  • large SA = for evaporation
  • interconnecting air spaces
  • stomata (pores) in leaves = to allow water to diffuse out of plants (to limit water loss - plant closes stomata)
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9
Q

Explain the mechanism by which water moves upwards in the xylem

A
  • Water evaporates from leaves creating negative pressure in xylem = TRANSPIRATION PULL
  • drawn up the xylem in a column (in continuous transpiration steam)
  • held together by cohesion
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10
Q

Define translocation

A
  • Movement of SUCROSE and AMINO ACIDS in phloem:
  • from SOURCE (regions of production) – to SINK (regions of storage OR to regions where they are used in respiration or growth)
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