Transport in plants

Question 1

Describe the mass flow hypothesis for the mechanism of translocation in plants

Answer 1

Source - Sugars actively transported into phloem by companion cells
Lowers water potential of sieve cells and water then enters by osmosis
Increase in pressure causes mass movement
Sugars converted in root for respiration for storage

Question 2

name the process that produces CO2 released from trunk of tree

Answer 2

Respiration

Question 3

Why does phosphate increase plant growth?

Answer 3

To produce DNA, RNA, ATP

Question 4

What does the xylem transport?

Answer 4

Water in the stem and leaves of the plant

Question 5

What is the cohesion tension theory?

Answer 5

Water molecules are attracted to eachother which forms a column of water

Question 6

Why does the xylem need to be structurally very strong?

Answer 6

The pull of water creates tension within the column

Question 7

What is capillary action?

Answer 7

Water molecules attracted to the side of xylem vessels (Adhesion)
As xylem is narrow these forces can pull water upwards

Question 8

What does the phloem transport?

Answer 8

Organic substances

Question 9

Similarities between starch and cellulose

Answer 9

Both are polysaccarides

Have glycosidic bonds

Question 10

Differences between starch and cellulose

Answer 10

Starch contains alpha glucose
Starch is helical
Starch has 1-6 branching

Question 11

How are sieve cells adapted for mass transport?

Answer 11

Very little cytoplasm

Thick/ strong walls to withstand pressure

Question 12

How are companion cells adapted for mass transport?

Answer 12

Many mitochondria for release of ATP for active transport

Question 13

How is high pressure generated in the leaves?

Answer 13

Water potential becomes lower as sugar enters
phloem
2. Water enters phloem by osmosis;
3. Increased volume of water causes increased pressure.

Question 14

In an investigation about the effect of a substance that inhibits uptake of sucrose on the rate of translocation, why is it important the rate of photosynthesis is kept the same?

Answer 14

The rate of photosynthesis is linked to the rate of sucrose production
Rate of translocation higher with a higher sucrose concentration

Question 15

Contrast the processes of facilitated diffusion and active transport

Answer 15

1. Facilitated diffusion involves channel or carrier proteins whereas active transport only involves carrier proteins;
2. Facilitated diffusion does not use ATP, active transport does
3. Facilitated diffusion takes place down a concentration gradient whereas
   active transport can occur against a concentration gradient.