Chapter 36 - 5

Question 1

What is the ATP dependent mechanism that moves sucrose into seive-tube elements?

Answer 1

It is called cell-mediated active transport. Companion cells, closely associated with sieve-tube elements in phloem use energy from ATP to transport sugar against concentration gradient into the sieve-tube elements. This process ensure efficient sugar transport, which is a crucial carb, through the phloem for distribution.

Question 2

What is the process of translocation?

Answer 2

The movement of organic nutrients, primarily sucrose, from the source to the sink. Phloem moves the Phloem sap.

Question 3

What is an experiment that can demonstrate the concentration of sugars in the phloem is higher than sugar source.

Question 4

What is usually the source for translocation?

Answer 4

Usually where photosynthesis occurs

Question 5

What is usually the sink for translocation?

Answer 5

Other parts that are in need of nutrients for growth or storage.

Question 6

What are some examples of sugar sources for plants?

Answer 6

Leaves and Storage roots or Tubers. These are producers of sugar by photosynthesis or starch breakdown.

Question 7

What are some examples of sugar sinks?

Answer 7

Growing roots, shoots, and fruits.
Storage roots and tubers

Question 8

What are specialized cells of the phloem that translocate sugars?

Answer 8

Sieve-tubes elements.

Question 9

Are sieve-tube cells alive?

Answer 9

Yes.

Question 10

Are xylem cells alive?

Answer 10

No.

Question 11

What are some sieve tube element stats?

Answer 11

They are arranged end to end
Devoid of most organelles
Have companion cells to support metabolism
Long and skinny
Separated by sieve tube plates that provide structure
Direction can be any direction

Question 12

What cell types make sugars through photosynthesis?

Answer 12

MESOPHYLL

Question 13

How do sugars enter the seive-tube elements?

Answer 13

Via symplast or apoplast

Question 14

What is often required due to sugar concentration being higher in the phloem?

Answer 14

Active transport

Question 15

What do ATP dependent proton pumps create?

Answer 15

A proton gradient

Question 16

What do proton gradient pumps do?

Answer 16

Pump sucrose against its concentration gradine using Hydrogen and sucrose cotransporters.

Question 17

Bulk flow needs what pressure?

Answer 17

Positive pressure.

Question 18

What are the 4 steps of bulk flow translocation?

Answer 18

1. sugar is loaded into sieve tube from source
2. water follows to maintain osmotic pressure
3. pressure is relieves as sugar and water are unloaded into sink
4. water enters xylem for recycling

Question 19

What does total water pressure do?

Answer 19

It increases and pushes phloem sap towards the sink.

Question 20

4 simple steps of translocation?

Answer 20

1. Loading of Sugar
2. Uptake of Water
3. Unloading of Sugar
4. Recycling of Water

Question 21

Where would there be a higher concentration of sugar be higher?

Answer 21

Near the source. The source is making the sugar. This can be proven by aphids.

Question 22

What is an experiment that could demonstrate the concentration of sugars in phloem is higher near sugar source?

Answer 22

Aphids (insects). Aphids suck phloem sap by injecting needle-like mouthpiece called stylet into sieve-tube. Plucking out aphid leaves the stylet inside. Sap would then run out of stylet. This showed that stylets injected near the source had much higher sap concentration.