Plant Nutrition

Question 1

what are heterotrophs

Answer 1

organisms unable to make their own food and obtain food by feeding on others

Question 2

what is the energy conversion in photosynthesis

Answer 2

chlorophyll traps light energy and converts it into chemical energy

Question 3

what is the chemical equation for photosynthesis

Answer 3

6CO₂ + 12H₂O —(light energy/chlorophyll)—> C₆H₁₂O₆ + 6O₂ + 6H₂O

Question 4

what is the word equation for photosynthesis

Answer 4

carbon dioxide + water —(light energy/chlorophyll)—> glucose + oxygen + water

Question 5

2 points

how do chlorophylls give the green colour in plants

Answer 5

chlorophylls are the main photosynthetic pigment in plants
they absorb red and blue-violet light, reflect green light
(refer to band of visible light segment of electromagnetic spectrum)

Question 6

2 points

what are the external structures of a leaf

Answer 6

lamina (leaf blade)
leaf stalk (petiole)

Question 7

2 points

what are the functions of the lamina

Answer 7

large surface area to maximise absorption of sunlight

thin lamina reduces distance and allows rapid diffusion of carbon dioxide to reach inner cells of the leaf

Question 8

1 point

what is the function of the leaf stalk

Answer 8

positions the lamina for maximum absorption of sunlight and gaseous exchange

Question 9

2 points

what are the functions of the network of veins in leaves

Answer 9

veins allow transport of water and mineral salts to cells of the lamina

transport manufactured food from leaves to other parts of the plant

Question 10

6 points

what are the internal structures of a leaf

Answer 10

cuticle
upper epidermis
palisade mesophyll
vascular bundle
spongy mesophyll
lower epidermis

Question 11

2 points

what is the cuticle and its function

Answer 11

waxy layer above epidermis which reduces excessive water loss

transparent to allow sunlight to penetrate to the mesophyll

Question 12

what is the upper epidermis

Answer 12

single layer of closely packed cells (no chloroplast)

Question 13

what is the palisade mesophyll and its function

Answer 13

a few layers of closely packed cells which are long, cylindrical

contain numerous chloroplasts for maximum absorption of light (where photosynthesis occurs)

Question 14

what is the vascular bundle and its function

Answer 14

contains xylem and phloem

allows for transport of water and food within the plant

Question 15

2 points

what is the spongy mesophyll and its function

Answer 15

irregularly shaped cells with numerous large intercellular air spaces (contains fewer chloroplasts than palisade mesophyll cells)

air spaces to allow for rapid diffusion of gases inside the leaf

Question 16

what is the lower epidermis

Answer 16

single layer of closely packed cells where many minute openings called stomata are found

Question 17

2 points

what are the characteristics of stomata

Answer 17

each stoma is surrounded by guard cells which control the size of stomata

stomata generally open in the light and close in the dark

*guard cells contain chloroplasts

Question 18

4 points

what happens to guard cells in presence of light

Answer 18

guard cells manufacture glucose by photosynthesis

water potential of guard cells decrease

water from adjacent epidermis cells (higher w.p.) enters guard cells (lower w.p.) by osmosis

guard cells swell and become turgid, causing them to become curved and pull the stoma open

Question 19

4 points

what happens to guard cells in absence of light

Answer 19

glucose is used up or converted to starch

water potential of guard cells increase

water exits to the adjacent epidermis cells by osmosis

guard cells become flaccid and stoma closes

Question 20

4 points

how does carbon dioxide enter the leaf

Answer 20

carbon dioxide is rapidly used up in the cell during photosynthesis

carbon dioxide concentration is lower than atmospheric air

carbon dioxide diffuses into leaf through stomata down a diffusion gradient

carbon dioxide dissolves into the film of water surrounding the mesophyll cells and diffuses into the cells

Question 21

2 points

how does water enter the leaf

Answer 21

water is brought to the leaves via the xylem vessels in the veins

water leaves the xylem and moves from mesophyll cell to mesophyll cell by osmosis

Question 22

5 points

what happens to glucose in plants

Answer 22

broken down by plant cells during cellular respiration to release energy

used to form cellulose cell wall

excess glucose temporarily stored as starch

can be used to form amino acids and fats

converted to sucrose which is transported to storage organs