chapter 6: plant nutrition

Question 1

photosynthesis

Answer 1

process by which plants synthesise carbohydrates from raw materials using energy from light

Question 2

what does chlorophyll do?

Answer 2

it transfers energy from light into energy in chemicals for the synthesis of carbohydrates

Question 3

outline 5 uses for the carbs made from photosynthesis

Answer 3

1. starch as an energy store
2. cellulose to build cell walls
3. glucose used in respiration to provide energy
4. sucrose for transport in the phloem
5. nectar to attract insects for pollination

Question 4

what are nitrate ions used for

Answer 4

to make amino acids

Question 5

what are magnesium ions used for

Answer 5

to make chlorophyll

Question 6

outline the pathway a carbon dioxide molecule taken when a leaf is photosynthesising

Answer 6

1. higher concentration of carbon dioxide in atmosphere compared to inside of leaf
2. carbon dioxide diffusion into the leaf through the open stomata into the air spaces in the spongy mesophyll
3. the carbon dioxide diffuses through the cell wall and cell membrane of the mesophyll cell, then dissolves into the cytoplasm and then diffuses into chloroplast

Question 7

describe the waxy cuticle

Answer 7

• protective layer on the top of the leaf that prevents water from evaporating
• thin and made of wax to protect the leaf without blocking light

Question 8

describe the upper epidermis

Answer 8

thin and transparent to allow light to enter the palisade mesophyll layer for photosynthesis

Question 9

describe the palisade mesophyll

Answer 9

• column shaped cells tightly packed together with chloroplasts to absorb more light, maximising photosynthesis
• light will hit the chloroplasts directly

Question 10

describe the spongy mesophyll

Answer 10

• contains internal air spaces to increase the surface area to volume ratio for the diffusion of gases
• air spaces allow carbon dioxide to diffuse through the leaf, increasing the surface area

Question 11

describe the lower epidermis

Answer 11

• contains guard cells and stomata
• stomata; site if gas exchange, mostly found on the underside of the leaf to reduce water loss

Question 12

describe the vascular bundle

Answer 12

• contains xylem and phloem to transport substances to and from the leaf
• thick cell walls of the tissue in the bundles help to support the stem and leaf
• xylem: transports water into the mesophyll cells for photosynthesis and for transpiration from stomata
• phloem: transports sucrose and amino acids around the plant

Question 13

why wou ld leaves have a large surface area?

Answer 13

to increase the syrface area available for the diffusion of carbon dioxide and absorption of light for photosynthesis

Question 14

why would leaves be thin?

Answer 14

allows carbon dioxide to diffuse to the palisade mesophyll cells quickly