Plant Transport Flashcards
Draw a diagram of a root cross section and label it
Should include epidermis, cortex, endodermis and vascular bundle with xylem and phloem
Draw a diagram of a stem cross section and label xylem and phloem
Vascular bundle should be in circles around outside. Xylem on inside phloem on outside
How are mineral ions like nitrate absorbed into root hair cells?
Active transport
Give two adaptations that root hair cells have.
Large surface area, many mitochondria and transport proteins
What is the apoplast pathway?
Movement of water through the cellulose cell wall
What is the symplast pathway?
Movement of water through the cytoplasm and plasmodesmata
Which is the fastest pathway for water through the root and why?
Apoplast is fastest because it has least resistance to flow, vacuolar is slowest because it has the greatest resistance due to the number of membranes that need to be crossed
Where is the Casparian strip located and what is it made of?
Endodermis cells, suberin (waterproof wax)
Why does water move into the xylem?
Cohesion and the transpiration stream, capillary action and root pressure
What is root pressure?
Mineral ions are actively transported from the endodermis into the pericycle. This lowers the water potential in the pericycle and water follows by osmosis
What is the function of the casparian strip?
To block the apoplast pathway and force water into the symplast pathway, meaning it must pass through a cell membrane
What four factors can affect the rate of transpiration?
Humidity, temperature, wind speed, light intensity
Why is water uptake in a plant not the same value as water lost by transpiration?
Water is used in photosynthesis and hydrolysis, made in respiration and used to increase turgor of cells
What does a potometer measure?
The distance moved by an air bubble in one minute, which can be used to calculate rate of water uptake
Describe the structure of the xylem
Dead tissue, divided into tracheids (narrower) and vessels (wider). Surrounded by waterproof lignin. Presence of pits
Describe the structure of the phloem
Living tissue. Companion cells packed with organelles, connected to sieve tubes by plasmodesmata. Sieve tubes have very reduced cell contents
How do sugars and amino acids move through the phloem?
Translocation, potentially by mass flow
List the problems with the mass flow theory
Presence of sieve plates, companion cells, mitochondria. Use of oxygen, stopped by cyanide, 10000x faster than diffusion
Give three alternative hypotheses to mass flow
Cytoplasmic streaming, protein filaments, active loading of phloem
Give the features of a xerophyte that help to reduce waterloss
Rolled leaves, sunken stomata, hairs. All of these trap water vapour and reduce the diffusion gradient.
