Nutrition and Transport in Flowering Plants

Question 1

Upper epidermis

Answer 1

The closely packed cells form one layer and do not contain chloroplasts

Question 2

Palisade mesophyll

Answer 2

The closely packed, long and cylindrical cells contain the most chloroplasts

Question 3

Spongy mesophyll

Answer 3

The loosely packed and irregular-shaped cells contain chloroplasts

Question 4

Lower epidermis

Answer 4

The closely packed cells form one layer and do not contain chloroplasts

Question 5

Overall function of epidermal layer

Answer 5

Function:
To regulate the secretion of metabolic substances

Question 6

Adaptation of leaves for photosynthesis

Answer 6

1. Waxy cuticle on epidermal layers
   - Reduces water loss through evaporation
   - Transparent to allow light to pass through
2. Stomata present in the epidermal layers
   - Stomata open in the presence of light, allowing carbon dioxide to diffuse in and oxygen to diffuse out of the leaf
3. Chloroplasts containing chlorophyll in all mesophyll cells
   - Chlorophyll absorbs energy from light and transfer it as chemical energy in glucose molecule
4. More chloroplasts in upper palisade tissue
   - More light can be absorbed near the upper leaf surface
5. interconnecting system of air spaces in the spongy mesophyll
   - The air spaces allow rapid diffusion of carbon dioxide and oxygen into and out of the mesophyll cells
6. Veins containing xylem and phloem found close to mesophyll cells
   - Xylem transport water and mineral salts to the mesophyll cell while the phloem transports glucose away from the leaf

Question 7

Stomata (Under Sunlight)

Answer 7

1. The guard cell carry out photosynthesis
2. The water potential decreases, so water enters the guard cells
3. The guard cells swell and become turgid, they become curved and the stoma opens

Question 8

Stomata (Hot and sunny day)

Answer 8

1. The leaf loses too much water to the atmosphere
2. The guard cell becomes flaccid and the stoma closes

Question 9

Xylem

Answer 9

Function:
- To transport water and mineral salts from the roots to other parts of the plant
- To provide mechanical support

Adaptation:
- It is a long hollow tube made up of dead cells without cross walls
- There is lignin on the inner walls

Question 10

Phloem

Answer 10

Function:
To transport glucose from the leaves to other parts of the plant

Adaptation:
- The sieve plates which are ‘cross-walls’ between the cells have many minute pores
- The companion cell of each sieve tube provides nutrients and helps it to transport food

Question 11

Companion cell (of phloem)

Answer 11

Function:
They have mitochondria to provide energy for the active transport of sucrose through the phloem in the leaves to other parts of the plant

Reason for more mitochondria:
More energy is required to load sugar from mesophyll cells into sieve tubes

Question 12

Photosynthesis

Answer 12

The process in which light energy is absorbed by chlorophyll to form glucose from carbon dioxide and water

Question 13

Factors that affect the rate of photosynthesis

Answer 13

1. Light intensity
2. Carbon dioxide concentraion
3. Temperature

Question 14

Relationship of temperature to the rate of photosynthesis

Answer 14

As the temperature increases, the kinetic energy of the reactant particles increases, causing an increase in frequency of effective collisions between reactants, forming more enzyme-substrate complexes.

However, when temperature exceeds optimum temperature, the rate of photosynthesis decreases drastically

Question 15

Limiting factor

Answer 15

Factor that affects the rate of reaction
(The rate of photosynthesis cannot increase unless the value of the factor increases)

Question 16

Translocation

Answer 16

Translocation is the transport of manufactured food substances such as sugars in the plant

Question 17

Ways that root hairs absorb mineral salts

Answer 17

1. Diffusion
   - When the concentration of mineral salts in the soil is higher than that in the root hair cells
   - Mineral salts diffuse down the concentration gradient into the root hair
2. Active transport
   - When the concentration of mineral salts in the soil is lower than that in the root hair cells
   - Mineral salts are absorbed against a concentration gradient into the root hairs

Question 18

Adaptation of root hair cells
(*Cell structure and organisation)

Answer 18

1. Long narrow extension
   - To increase SATV for greater rate of diffusion of water and mineral salts into the root hair cells
2. Has a cell membrane
   - Prevent cell sap from leaking out
3. Have many mitochondria
   - Provide energy for the active transport of mineral salts into the root hair cells

Question 19

Transpiration

Answer 19

Transpiration is the loss of water vapour from different parts of the planets, mainly through stomata in the leaves

Question 20

Transpiration pull

Answer 20

The suction force dues to transpiration

Question 21

Water movement inside a leaf

Answer 21

1. Water from the thin film of moisture surrounding the mesophyll cells evaporate to form water vapour in the intermolecular air spaces
2. Water vapour diffuses out of the stomata into the surrounding air (Transpiration)
3. As water evaporates from the thin layer of moisture, more water moves out of the mesophyll cells causing the water potential of these cells to decrease
4. Water is drawn from cells deeper inside the leaf by osmosis
5. Water is eventually drawn from the xylem via osmosis, and this creates a suction force that pulls the column of water up the xylem, called transpiration pull

Question 22

Factors affecting rate of transpiration

Answer 22

1. Wind
   - Wind blows away water vapour that diffuses out of a leaf
2. Temperature
   - When temperature increases, water evaporates within the cell faster
3. Light
   - When there is more light, the stomata opens wider
4. Humidity
   - The amount of moisture in the surrounding air affects the concentration gradient of water vapour between the leaf and the surrounding air

Question 23

Notes

Answer 23

1. Glucose is converted to sucrose for transport