LABORATORY REVIEW
TRANSPIRATION
|
Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
|
|
|
by active transport of H+ ions to create a proton gradient and co transport back into companion cells
|
|
|
By active transport of sucrose to create a diffusion gradient
|
|
|
By diffusion of H+ ions into the phloem taking sucrose with them
|
|
|
By osmosis of water to change the water potential
|
Detailed explanation-1: -The cotransport of a proton with sucrose allows movement of sucrose against its concentration gradient into the companion cells. occurs. From the companion cells, the sugar diffuses into the phloem sieve-tube elements through the plasmodesmata that link the companion cell to the sieve tube elements.
Detailed explanation-2: -Sucrose enters the companion cell against the concentration gradient, increasing the concentration of sucrose in the cell. Sucrose diffuses down a concentration gradient from the companion cell into the sieve tube element through plasmodesmata.
Detailed explanation-3: -Hydrogen ions move back into the companion cell down their concentration gradient through a co-transporter protein. Whenever a hydrogen ion moves through the co-transporter, a sucrose molecule is also transported into the companion cell, against its concentration gradient.
Detailed explanation-4: -The sucrose is actively transported against its concentration gradient (a process requiring ATP) into the phloem cells using the electrochemical potential of the proton gradient. This is coupled to the uptake of sucrose with a carrier protein called the sucrose-H+ symporter.