Mass transport in plants (xylem)

0.0(0)
studied byStudied by 0 people
learnLearn
examPractice Test
spaced repetitionSpaced Repetition
heart puzzleMatch
flashcardsFlashcards
Card Sorting

1/11

flashcard set

Earn XP

Description and Tags

Biology

Study Analytics
Name
Mastery
Learn
Test
Matching
Spaced

No study sessions yet.

12 Terms

1
New cards

What are the two parts of a plant involved in mass transport of substances and what do they transport?

  • Xylem → transport of water and mineral ions from the roots up to the leaves.

  • Phloem → transport of food substances (sugars) from where they are produced in the leaves by photosynthesis to parts of the plant that need it for respiration (all cells).

2
New cards

What functions does water have in plants?

  • Cell turgidity

  • Metabolite in photosynthesis

  • Hydrolysis reactions

  • Transporting inorganic ions

3
New cards

How is water absorbed in the roots?

  • Through root hair cells, water moves in by osmosis down a water potential gradient.

  • Mineral ions are taken in by active transport.

4
New cards

What are some features of root hair cells?

They’re extensions on some of the root epidermal cells and have a thin cell wall (short diffusion pathway), large SA and lots of mitochondria (release ATP which provides energy for active transport of mineral ions).

5
New cards

Describe the structure of a xylem vessel.

  • Hollow/continuous because the cells have no end walls.

  • Lignified as the cells that make up the xylem mature, a substance called lignin builds up in their cell walls;

  • This causes the cells to die and lose their end walls, cytoplasm and organelles making it a long continuous tube.

  • The lignin often forms in rings or spirals/helices and makes the xylem very rigid.

<ul><li><p>Hollow/continuous because the cells have no end walls.</p></li><li><p>Lignified as the cells that make up the xylem mature, a substance called lignin builds up in their cell walls;</p></li><li><p>This causes the cells to die and lose their end walls, cytoplasm and organelles making it a long continuous tube.</p></li><li><p>The lignin often forms in rings or spirals/helices and makes the xylem very rigid.</p></li></ul>
6
New cards
  1. Describe how water moves through the xylem.

  1. Pulling force (transpiration stream)- bulk transport of water up the stem of a plant through the xylem vessels, due to evaporation of water from the leaves (negative force).

  2. Root pressure- water taken into the roots by osmosis providing a pushing force (positive force.

  3. Capillary action- assisting in the xylem vessels, combination of adhesion and cohesion, aids upward movement of water.

7
New cards

Describe capillary action.

  • Water is polar- uneven distribution of charge - one side is slightly positive and one slightly negative;

  • This causes extensive hydrogen bonding which makes water cohesive → as well as water molecules sticking to each other, they also stick to xylem walls (adhesion).

8
New cards

How does water moves out of the stomata?

  • There’s a water potential gradient between the inside of the leaf and the outside (higher in substomatal air spaces and lower in the atmosphere).

  • Moves down its water potential gradient- evaporating out the stomata (due to thermal energy from the sun).

  • As one water molecule moves forward and evaporates out, this pulls the whole continuous column if water up.

<ul><li><p>There’s a water potential gradient between the inside of the leaf and the outside (higher in substomatal air spaces and lower in the atmosphere).</p></li><li><p>Moves down its water potential gradient- evaporating out the stomata (due to thermal energy from the sun).</p></li><li><p>As one water molecule moves forward and evaporates out, this pulls the whole continuous column if water up.</p></li></ul>
9
New cards

What’s the cohesion-tension theory?

That water being pulled up the plant (sucked up-transpiration pull), causes tension in the xylem vessels- slightly pulls in the xylem walls and reduces diameter of the stem/trunk.

10
New cards

What equipment can be used to measure the rate of transpiration?

Potometer

11
New cards

How do potometers work?

  • If cells of a plant are fully turgid, then the rate of water uptake/absorption + rate of transpiration are roughly the same.

  • By introducing a bubble, you can watch the bubble move along and time how much water is taken up in a set amount of time.

<ul><li><p>If cells of a plant are fully turgid, then the rate of water uptake/absorption + rate of transpiration are roughly the same.</p></li><li><p>By introducing a bubble, you can watch the bubble move along and time how much water is taken up in a set amount of time.</p></li></ul>
12
New cards

What factors affect the rate of transpiration?

  • Temperature (increase)

  • Light (increase)

  • Air movement (increase)

  • Humidity (decrease)

    If you change one factor, the others must be kept constant.