Ch.34-36 Exam

Question 1

Where does most of the mass of a plant come from? (Hint: Where does it NOT come from?)

Answer 1

• Most mass of a plant comes from atmosphere and water, not soil

Question 2

Define essential nutrient.

Answer 2

An element or compound required for normal growth and production

Question 3

Define macronutrients. What are macronutrients major components of in plants?

Answer 3

• Elements in the soil that plants require in large quantities.
• Major components of nuclei acids, phospholipids, and proteins

Question 4

What three macronutrients make up 96% of the dry weight of a plant?

Answer 4

C,H, and O 96% of dry weight of a plant

Question 5

What are the three limiting macronutrients found in plants? (Hint: They are major ingredients of all fertilizers!)

Answer 5

• Nitrogen (N)
• Phosphorous (P)
• Potassium (K)

Question 6

What are some examples of micronutrients? What are some of their functions?

Answer 6

• Iron, zinc, copper, and nickel
• Function as cofactors of specific enzymes

Question 7

What are the three sources nutrients can be obtained from? In which source is oxygen, carbon, and hydrogen obtained from? In which are the other macronutrients obtained
from? The micronutrients?

Answer 7

• From water, air, and soil
• Oxygen: O2, H2O
• Carbon: CO2
• Hydrogen: H2O
• Micronutrients: soil
• Macronutrients: soil

Question 8

Explain how anions and cations behave differently. Which is more readily available for plant absorption, and why?

Answer 8

• Anions tend to dissolve in soil water —> readily available for plant absorption
• Cations tend to interact with negative charges of organic matter and clay —> harder for plants to absorb

Question 9

Explain cation exchange. What produces the H+ ions to help cation exchange?

Answer 9

• Cation exchange occurs when protons (H+) bind to negative charges on soil particles —> release bound cations for uptake
• Plant roots release CO2, which interacts with H2O forming carbonic acid, which releases H+, enabling uptake of cations

Question 10

Define the zone of maturation.

Answer 10

• Zone of maturation —> region just above the growing root tip

Question 11

Define root hair’s function.

Answer 11

• Contain root hairs —> increase the surface area available for nutrient and water absorption

Question 12

Explain how proton pumps generate an electrochemical gradient. What is the net charge both outside of the cell and inside of the cell?

Answer 12

• Active transport —> requires ATP
• Protons are pumped out of the cells —> outside of the cell becomes more positive
• In comparison, the inside of the cell becomes more negative

Question 13

The electrochemical gradient encourages cations to enter the cell. Explain how anions must enter the cell through cotransporters.

Answer 13

• So much energy is released when a proton enters the cell along its electrochemical gradient that anions can be co-transported against their electrochemical gradients

Question 14

Explain mycorrhizal fungi’s role in helping nutrient uptake in plants.

Answer 14

• Increase the plant’s surface area!
• provide nitrogen and phosphorous (limiting factors)
• Fungi receives sugar from the plant

Question 15

Explain the interaction between nitrogen fixing bacteria and plants.

Answer 15

• Certain bacteria are able to perform nitrogen fixation —> convert N2 into ammonia, nitrates, and nitrites
• Bacteria takes up residence inside plant roots —> nodules
• Bacteria provides plant with nitrogen in exchange for sugar and protection

Question 16

Name and describe the two plant vascular tissues.

Answer 16

Xylem: conducts water and dissolved ions from the root system to the shoot system

Phloem: conducts sugar, amino acids, chemical signals and other substances back and forth between the root system and the shoot system

Question 17

What is the xylem composed of?

Answer 17

Tracheids and vessel element

Question 18

What is the phloem composed of?

Answer 18

Sieve-tube elements and companion cells

Question 19

How does water flow through areas? (Hint: Low water potential to high? Or high to low?)

Answer 19

Water always flows from areas of high water potential to areas of low water potential

Question 20

Define solute potential and pressure potential.

Answer 20

Solute potential —> tendency of water to move by osmosis

Pressure potential —> tendency of water to move due to pressure

Question 21

What is the equation for potential energy of water?

Answer 21

W= Wp + Ws

Question 22

Explain how water is transported from the roots and the shoots, specifically through water potential.

Answer 22

• Soil and roots have a high water potential
• Warm and dry air has a low water potential
• This relative difference creates a water-potential gradient
• As transpiration (loss of water via evaporation) occurs —> water moves down its water-potential

Question 23

Define translocation.

Answer 23

The movements of sugars (sucrose) through a plant from sources to sinks via phloem

Question 24

Define source and sink. Give examples of sources and sinks on a plant.

Answer 24

Source —> a tissue where sugar enters the phloem
- Ex: Flowers, young leaves, lateral meristems, roots

Sink—> a tissue where sugar exits the phloem
- Ex: Mature leaves, vascular tissue

Question 25

Define phloem loading.

Answer 25

Phloem loading —> sucrose is moved by active transport from source cells into the phloem —> high concentration of sucrose in phloem

Question 26

Explain water movement in and out of the xylem according to the level of sucrose in the phloem. (Hint: Water will leave the xylem when it’s near high concentrations of sucrose.)

Answer 26

• Water from adjacent xylem vessels passively moves into the phloem
• Sucrose in the phloem moves (actively or passively) from the phloem into sink cells
• As concentration of sucrose decreases in the phloem, water flows back into the xylem