Adaptation For Transport In Plants Flashcards
Describe structure of roots and how this is beneficial to the plant
- xylem is central and star shaped
- phloem between groups of xylem cells
- resists vertical stresses and anchors plant in soil
Describe the structure of stems and how this is beneficial to the plant
- vascular bundles are in a ring at the periphery: xylem towards the centre, phloem towards the outside
- gives flexible support and resists bending
Describe the structure of leaves and how this is beneficial for the plant
- vascular tissue in the midrib and in a network of veins
- flexible strength and resistance to tearing
What are the main cell types in xylem?
Vessels and tracheids
What plant do tracheids occur?
Ferns, conifers and angiosperms
Why do mosses not grow as tall as other plants?
No water conducting tissue
Poorer at transporting water
What are the only plants that vessels occur in?
Angiosperms
What are the functions of xylem?
- Transport of water and dissolved minerals
2. Providing mechanical strength and support
How is water taken up by roots?
- soil water contains dilute solution of mineral salts- high water potential
- vacuole and cytoplasm of root hair cell have concentrated solution of diluted- more negative water potential
- water passes into root hair cell by osmosis
What is the apoplast pathway?
Water moves in the cell walls
Cellulose fibres in the cell wall are separated by spaces through which the water moves.
What is the symplast pathway?
Water moves through the cytoplasm and plasmodesmata
What is the plasmodesmata?
Strands of cytoplasm through pits in the cell wall joining adjacent cells.
What is the vacuolar pathway?
Water moves from vacuole to vacuole
What is transpiration?
The evaporation of water vapour from the leaves or other above ground parts of the plant, out through stomata into the atmosphere.
What are the genetic factors affecting the rate of transpiration?
Number, distribution and size of stomata.
What are the environmental factors affecting the rate of transpiration?
Temperature
Humidity
Air movement
Light intensity
How does temperature affect transpiration rate?
Increase in temperature increases kinetic energy
Water diffuses away from leaf quicker
Reduces water potential of atmosphere around the leaf
How does humidity affect rate of transpiration?
Air inside leaf is saturated with water vapour- relative humidity is 100%
Water potential gradient between leaf and atmosphere
Stomata open- water diffuses out of leaf
How does air movement affect rate of transpiration?
Blows away layer of humid air at the leaf surface
Water potential gradient increases- water vapour diffuses out quicker
How does light intensity affect the rate of transpiration?
Stomata open wider as light intensity increases
How do MESOPHYTES ( plants living in conditions of adequate water supplies) survive in times when water is not available?
- shed leaves ( do not loose water through transpiration)
- aerial parts die off so they are not exposed to cold weather
- dormant seeds over winter- low metabolic rate
Marram grass is a XEROPHYTE. How is it adapted to live in low water availability?
- rolled leaves: reduces leaf area exposed - reduces transpiration
- sunken stomata- humid air is trapped in pit, reduces water potential gradient
- hairs- trap water vapour- reduce gradient
- thick waxy cuticle- waterproof- reduces water loss
How are HYDROPHYTES ( plants that grow in water) adapted?
- water is supportive medium- little or no lignified tissues
- surrounded by water- transport not needed- xylem poorly developed
- leaves no cuticle- don’t need to prevent water loss
- stomata on upper surface of floating leaves, lower surface is in water
- stems and leaves have large air spaces- reservoir for o2 and co2- provide buoyancy
What is translocation?
The active movement of the soluble products of photosynthesis, such as sucrose and amino acids, through phloem, from sources to sinks.
