2.53 - 2.58B Flashcards
what do phloem vessels transport
food materials (sucrose and amino acids)
what is the role of xylem vessels
to transport water and dissolved minerals from the roots to the leaves
in which direction is the phloem transporting the nutrients
it varies depending on where the source is and where the nutrients are needed
where in the cross section of a root is the xylem and phloem
the xylem is on the inside and the phloem is on the outside
2 key structural features of the xylem
- it is composed of dead cells which form hollow tubes
- the xylem cells are strengthened by lignin and are adapted for the transport of water in the transpiration stream
adaptations of the root hair cell to carry out its function
- single celled
- contain mitochondria which release energy for active transport
- increase the surface area
what is transpiration
the loss of water vapour from the parts of the plant that arre above ground
what are the functions of transpiration
- transporting mineral ions
- providing water to keep the cells turgid
- providing water to leaf cells for photosynthesis
- cools the plant
what are the 4 factors which affect transpiration
- air movement
- humidity
- temperature
- light intensity
how does air movement affect transpiration rate
there is more transpiration
- the good air flow removes water vapour from the air surrounding the leaf. this creates a concentration gradient encouraging water loss (between air and leaf)
how does humidity affect transpiration rate
there is less transpirations
- the concentration gradient is weaker when there is already water vapour in the air.
how does light intensity affect transpiration rate
there is more transpiration
- guard cells respond to high light intensity and open the stomata allowing water to be lost
how does temperature affect transpiration rate
there is more transpiration
- particles have more kinetic energy at higher temps. so transpiration occurs faster as water molecules evaporate from the mesophyll faster.
