13 Ass 7 pt 1 Plant Transport Flashcards
what DO phloem sieve tube elements have? 9
Cellulose cell walls,
cell membrane
cytoplasm
endoplasmic reticulum
Lots of mitochondria
end walls
sieve plate
companion cells
plasmodesmata
what DON’T phloem sieve tube elements have? 5
Nucleus
ribosomes
lignin
pits
spiral structures
What DO xylem vessel elements have? 3
Lignin cell walls
pits
spiral structures
what DON’T xylem vessel elements have? 5
nucleus
sieve plates
mitochondria
cytoplasm
end walls
Why do xylem vessel elements have pits btw vessels?
To allow water to pass from vessel to vessel
Why are xylem vessel elements thickened with lignin?
To stop them collapsing when water column is under tension
Why do xylem vessel elements form a continuous hollow tube through plant?
It provides little resistance to water movement
What is the ratio of cell wall width to whole cell width in a xylem vessel element?
around 1:10, cell wall is very thick
Under a microscope, what structures would likely be observed in a xylem vessel element?
None
What’s the ratio of cell wall width to whole cell width in a Phloem sieve tube element?
around 1:20, cell wall thinner than xylem
Under a microscope, what structures would likely be observed in phloem sieve tube elements?
regular pattern of circles in some cells
Under a microscope, what would likely be observed in companion cells?
granular appearance
What DO companion cells have? 4
Lots of mitochondria
lots of ribosomes
highly metabolically active
lots of plasmodesmata
What contributes to upward movement of water in a xylem vessel of a plant? 6
Cohesion of water molecules
- through hydrogen bonding
Adhesion of water molecules to the cellulose walls of xylem vessels
- by hydrogen bonding
removal of water from xylem vessels in a leaf
- reduces hydrostatic pressure in xylem
What term is used to describe the attraction of water molecules to each other?
cohesion
What is the sequence of parts of the root that the water must travel through to move across the root? 3
Cell walls of cortex cells
endodermal cells
Xylem vessels
Why is transpiration an inevitable consequence of gas exchange in plants?
Stomata must be open
What is an example of a mass flow system in a plant?
The movement of sap through the phloem sieve tubes in the stem
Q13 look at graph and read context. What can be concluded from the graph? 3
The rate of water absorption and the rate of water loss peak at 16:00
The rate of water loss is greater than the rate of absorption for 12 hours
The rate of water absorption is greater than the rate of water loss at night
The diameter of a tree trunk usually decreases slightly during the day. what changes in environmental factors during the day could cause the diameter to decrease more? 3
Increased light intensity
Increased wind speed
increased temperature
Q15 A student wanted to find the rate of transpiration using a potometer as shown. The student was told to work out the value for transpiration using units mm^3, m^-2, and hour^-1. Which measurements would the student need to take? 4
distance air bubble moves,
radius of capillary tubing,
time
surface area of the leaves
SUCROSE IS LOADED into phloem sieve tubes from companion cells. What is the correct order of statements that explains this mechanism? 4
Hydrogen ions are pumped out of companion cells by active transport
Hydrogen ions diffuse into companion cells through co-transporter proteins
sucrose is co-transported along with hydrogen ions
sucrose diffuses into phloem sieve tubes via plasmodesmata
Which sequence of events could lead to MASS FLOW in a phloem sieve tube? 6
Protons (H+) are actively pumped out of a companion cell
Protons (H+) and sucrose molecules move into a companion cell through a co-transporter protein
sucrose moves into a sieve tube element
The water potential of sieve tube element decreases
Water moves down water potential gradient by osmosis
A very high hydrostatic pressure is produced
What are proton pumps (H+ pumps) and co-transporters are used for?
Used in plants plants when loading sucrose into a phloem sieve tube element at a source.
