Nutrition + Transport in Plants

Question 1

What conditions are needed for Photosynthesis to occur?

Answer 1

• Light
• Chlorophyll
• Carbon Dioxide
• Water
• Suitable temperature
• Enzymes

Question 2

What is a variegated leaf?

Answer 2

A leaf that does not completely contain chlorophyll

Question 3

What is the light stage of photosynthesis?

Answer 3

Light energy is used to split water into oxygen gas and hydrogen atoms

Question 4

What is the dark stage of photosynthesis?

Answer 4

Chemical energy is used to convert carbon dioxide and hydrogen atoms into glucose and water

Question 5

What is the chemical equation of photosynthesis?

Answer 5

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Question 6

Which wavelengths of light produce the highest rate of photosynthesis?

Answer 6

Red and Violet-blue; They are the furthest away from green light, which is reflected.

Question 7

What can glucose be used for in plants?

Answer 7

• Respiration
• Converted to sucrose for transport
• Converted to cellulose for cell walls
• Converted to fats/proteins
• Converted to starch for storage

Sucrose is more stable, hence better for transport
Starch cannot move through cell membranes, so it stays where it is and is easier to store

Question 8

What additional materials are needed by plants? (apart from those used in photosynthesis)

Answer 8

Nitrate: Used in proteins and chlorophyll
Magnesium: Used in chlorophyll

idk if this is FYI or not

Question 9

What are the advantages and disadvantages of having thin leaves?

Answer 9

Advantages:
* No cells lie far from the surface
* Easier to absorb light/CO₂

Disadvantages:
* More at risk of water loss

Question 10

What are the parts of a leaf?

Answer 10

Lamina (leaf blade), Veins, Mid-rib, Petiole (stalk)

Question 11

What are the characteristics of the Palisade Mesophyll and Spongy Mesophyll layers in a leaf?

Answer 11

Palisade Mesophyll: Long thin cells, closely packed, more chloroplasts
Spongy Mesophyll: Irregularly shaped cells, loosely packed (many air spaces), fewer chloroplasts

Question 12

What is a cuticle and what is its function?

Answer 12

It is a transparent waxy layer around the leaf that prevents excessive water loss while still allowing sunlight through

Question 13

When do stomata open and close?

Answer 13

Open in the day to allow gaseous exchange for photosynthesis, close at night to prevent excessive loss of water vapour

Question 14

How do stomata open and close?

Answer 14

To open, the potassium concentration in the guard cells increases, causing water to be drawn in through osmosis, making them swell and become curved open. To close, the concentration decreases and the reverse happens.

Check Topic 5 slides for a more detailed explanation of the closing

Question 15

What are the characteristics of the leaves of land plants and aquatic plants?

Answer 15

Land plants: More stomata on lower surface, closely packed Palisade Mesophyll, single layer of Palisade Mesophyll
Aquatic plants: More stomata on upper surface, air chambers between Palisade Mesophyll, 2 layers of Palisade Mesophyll

Question 16

How do plants take in CO₂?

Answer 16

As CO₂ is used up, its concentration in the leaf decreases, allowing atmospheric CO₂ to diffuse into the leaf, and into the cells by dissolving the layer of water around them.

Question 17

What is a limiting factor?

Answer 17

A factor that directly affects a process if its quantity is changed.

Question 18

What is the position of xylem and phloem in Dicotyledonous plants?

Answer 18

In roots and stem, xylem is on the inside and phloem is on the outside. In leaf, xylem is on top and phloem is on the bottom.

Question 19

What are the characteristics of the xylem and phloem vessels in plants?

Answer 19

Xylem: Continuous lumen, lignified walls for support
Phloem: Presence of sieve plates and companion cells, small amounts of lignin

Lumen just means open space in this case; Lignin is a polymer that supports the xylem vessels

Question 20

What is the purpose of companion cells in phloem?

Answer 20

To provide energy for the phloem cells as they have very little protoplasm (living parts)

Question 21

How do roots absorb water and mineral salts?

Answer 21

Water: Osmosis
Mineral Salts: Diffusion when soil has higher concentration; Active Transport when soil has lower concentration

Question 22

What is root pressure?

Answer 22

Pressure resulting from the constant entry of water into the roots

Question 23

What is cohesion and adhesion?

Answer 23

Cohesion: Attraction of water molecules to each other
Adhesion: Attraction of water molecules to other molecules (usually sides of container)

Adhesion is what causes meniscus to form and capillary action to occur

Question 24

What is a transpiration pull?

Answer 24

The suction force created by water molecules leaving the plant due to transpiration. This causes water to be sucked up the xylem in a transpiration stream.

Question 25

What is a boundary layer and its purpose?

Answer 25

An unstirred layer of air close to the surface of the leaf. It reduces the leaf’s rate of water loss by making the water potential gradient between the inside and outside of the leaf less steep.

Question 26

What factors affect the thickness of the boundary layer?

Answer 26

• Wind speed
• Presence of leaf hair (trichomes)
• Presence of sunken stomata

Question 27

What causes wilting?

Answer 27

When a plant loses more water than it takes in, causing its cells to lose their turgor pressure and become plasmolysed.

Question 28

What are the advantages and disadvantages of wilting?

Answer 28

Advantages:
* Reduces rate of water loss
* Cools plant

Disadvantages:
* Stomata closes, decreasing CO₂ intake
* Leaves droop, decreasing absorbtion of sunlight

Question 29

What is a sugar source and sink?

Answer 29

Source: A plant organ that produces sugar

Sink: A plant organ that is a net consumer of sugar

A storage organ like a potato can be both a source and a sink.

Movement of sugars occurs from sources to sinks

Question 30

What is translocation?

Answer 30

Movement of food/mineral salts in a plant

Question 31

What causes bulging to occur when phloem is removed in a part of a plant stem?

Answer 31

Sugar cannot flow through that region of the stem, causing the cells near it to have a decreased water potential, hence water is drawn into the cells at that part of the plant causing it to swell.