plant transport

Question 1

what is the apolast pathway

Answer 1

• the water flows into the cellulose fibers
• it then seeps across into the roots from cell to cell and does not enter the cytoplasm

Question 2

what is the symplast pathway

Answer 2

• water moves into the cytoplasm by osmosis
• it then moves across the plasma membrane via plasmodesmata to the xylem

Question 3

what is the vacuolar pathway

Answer 3

• water moves in via osmosis to the vacuoles
• it has to cross the plasma membranes
• the resistance is high and not a lot of water moves this way

Question 4

how does nitrogen enter the plants

Answer 4

• normally enters as nitrogen ions or ammonium ions
• they diffuse with water in the apolast pathway and soaks into the cellulose fibers
• when they reach the endodermis, they enter via the symplast pathway by active transport, they by pass the casparian band

Question 5

what is the casparian strip

Answer 5

• its a waterproof layer in the endodermis of plant cells
• made out of a waxy, waterproof substance called suberin
• blocks the apolast pathway

Question 6

what is transpiration

Answer 6

• the loss of water vapour off of the surface of the leaves
• the continuous loss of water allows for a greater tension in the xylem which pulls water up through the xylem and to the leaves

Question 7

list some factors that affect transpiration rates

Answer 7

• temperature
• humidity
• light intensity
• air movement

Question 8

how do you measure the rate of water absorption

Answer 8

• using a potometer

Question 9

what is translocation

Answer 9

• products of photosynthesis are transported away from the source to areas of the plant, where they are used for growth or storage
• called the mass flow theory

Question 10

what are some features of root hair cells

Answer 10

• large surface area for water to enter by osmosis
• cellulose cell wall is freely permeable to water
• large number of mitochondria to provide ATP for active transport
• large number of protein carriers embedded in the membrane for active transport of mineral ions

Question 11

how does light intensity affect transpiration

Answer 11

• this affects the degree that the stoma are open or closed
• when there’s more light, the stomata are open more as more photosynthesis tales place, this means more water can be lost from the wider stomatal pores

Question 12

how does the temperature affect transpiration

Answer 12

• higher temperatures increase the kinetic energy of the water molecules so they diffuse more quickly
  warm air also has more kinetic energy so it holds more water

Question 13

how does humidity affect transpiration

Answer 13

• dry air creates a steeper concentration gradient
• high humidity reduces the gradient and reduces transpiration

Question 14

how does air movement affect transpiration

Answer 14

• maintains a diffusion gradient
• the humid air is blown away and replaced by cooler air which holds less water

Question 15

how do you measure the rate of water absorption

Answer 15

• measured using a potometer

Question 16

describe a method for measuring the rate of water absorption

Answer 16

• a leafy shoot is cut at an angle and inserted under water, this ensures an air tight fit and no air bubbles enter the xylem
• an air bubble is then seen
• measure 1 minute and record the distance the bubble has moved
• repeat 3 times and calculate a mean result

Question 17

how do you set up a potometer

Answer 17

• submerge it under water
• remove and fill ensuring there are no air bubbles
• do this by squeezing the rubber tubing and ensuring that all the air bubbles are removed
• make sure there is a constant flow of water around the potometer