weighted assessment 3

Question 1

what are the two transport tissues in a plant

Answer 1

xylem tissue and phloem tissue

Question 2

what are the two functions of the xylem tissue

Answer 2

1. conducting water and dissolved mineral salts from the roots to the other parts of the plant
2. providing mechanical support to the plant

Question 3

what is a xylem vessel

Answer 3

a xylem vessel is a long hollow tube stretching from the roots to the leaf

Question 4

what is photosynthesis

Answer 4

photosynthesis is the process by which plants take in carbon dioxide and water, and in the presence of light, manufacture glucose

Question 5

what is the chemical equation for photosynthesis

Answer 5

6CO2 + 6H2O → C6H12O6 + 6O2 + 6H2O

Question 6

describe the light-dependent stage

Answer 6

light is trapped by chlorophyll. it is converted to chemical energy and used to split water molecules
photolysis of water releases oxygen gas and hydrogen atoms
light stage drives the light independent stage

Question 7

describe the light-independent stage

Answer 7

reactions are catalysed by a series of soluble enzymes
glucose is formed using chemical energy and hydrogen atoms released during the light stage
formation of glucose is a reduction reaction as carbon dioxide gains hydrogen atoms

Question 8

what are the factors controlling photosynthesis

Answer 8

1. light intensity
2. carbon dioxide concentration
3. temperature

Question 9

what is the external leaf structure of a leaf made of and what are the respective functions

Answer 9

1. lamina (leaf blade)
   - large surface area to volume ratio to trap maximum amount of sunlight and to allow rapid diffusion of carbon dioxide
2. petiole (leaf stalk)
   - holds the laminate away from the stem
   - may or may not be present in all varieties
3. vein network
   - transport water and mineral salts to cell in lamina
   - transport manufactured food from lamina to other parts of the plant
   - veins may be branching or parallel

Question 10

what is the internal leaf structure of a leaf made of

Answer 10

1. upper epidermis layer
2. mesophyll layer
   - palisade mesophyll layer
   - spongy mesophyll layer
3. vascular bundle
   - xylem tissue
   - phloem tissue
4. lower epidermis
5. guard cells

Question 11

what is the purpose of the upper epidermis layer

Answer 11

• protects inner layer of cells (single uppermost layer of cells)
• reduces evaporation (thin layer of moisture)
• allows light to pass through (transparent)

Question 12

what is the purpose of the palisade mesophyll layer

Answer 12

• vertical arrangement exposes many cells to light rays

- photosynthesis takes place mainly here

Question 13

what is the purpose of the spongy mesophyll layer

Answer 13

• air spaces allow rapid diffusion to take place
• gases entering the cells can dissolve in the water
• photosynthesis takes place in these cells

Question 14

what is the purpose of the lower epidermis

Answer 14

• protects the inner tissue
• slows down water loss
• regulate opening & closing of the stomata for diffusion of carbon dioxide and oxygen in and out of the leaf

Question 15

what is the purpose of the guard cells

Answer 15

they control the size of the stoma which affect the rate of gaseous exchange in the leaf in the day and night

Question 16

what does the xylem transport

Answer 16

water and mineral salts

Question 17

what does the phloem transport

Answer 17

sucrose and amino acids

Question 18

what is the function of the roots

Answer 18

• holds plant firmly

- absorb water and dissolved mineral salts from the soil and distribute to the various parts of the plant

Question 19

what is transpiration

Answer 19

• it is the loss of water vapour from the stomata of the plant
• main force that draws from the soil and through the plant
  (water evaporates –> suction force which pulls water up the vessels in the vascular bundles against gravity)

Question 20

what are the factors affecting transpiration?

Answer 20

1. light intensity
2. humidity
3. wind speed
4. temperature

Question 21

when does root pressure happen

Answer 21

when water enters the root hair cells and the cortical cells and the cell becomes turgid
this turgidity generates a pushing force called root pressure