nutrition in plants

Question 1

photosynthesis

Answer 1

-6CO2 + 6H2O (light energy and chlorophyll)—> C6H12O6 + 6O2
-stage 1 - light-dependent reactions
-stage 2 - light-independent reactions

Question 2

light-dependent reaction

Answer 2

-light energy is used for the photolysis of water occurs to split water molecules into hydrogen ions, electrons and oxygen gas
-occurs in thylakoids and grana

Question 3

light-independent reaction

Answer 3

-carbon dioxide reduced by hydrogen ions with energy released from ATP, hence forming glucose molecules
-occurs in the stroma of the chloroplast in the presence of enzymes

Question 4

rate of photosynthesis can be measured

Answer 4

-dry mass formed per unit time
-volume of oxygen evolved per unit time
-volume of carbon dioxide absorbed per unit time

Question 5

limiting factors in photosynthesis

Answer 5

-light intensity is a limiting factor for the light-dependent stage
-the rate of photosynthesis is highest at the red and blue-violet regions of the action spectrum and lowest at the green region
-temperature is a limiting factor as the rate of enzyme reactions are affected during light-dependent and -independent stages
-carbon dioxide concentration is a limiting factor for the light-independent stage

Question 6

lamina/ leaf blade

Answer 6

-flat and large to maximise absorption of light energy and allow rapid diffusion of carbon dioxide to reach the mesophyll cells of leaf for photosynthesis

Question 7

network of veins

Answer 7

-allow transport of water and ions to the leaf cells, and transport nutrients away from cells to other parts of the plant

Question 8

petiole

Answer 8

-positions the lamina for maximum absorption of light energy and gaseous exchange

Question 9

cuticle

Answer 9

-waxy layer on both epidermal layers which reduce excessive water loss from epidermal cells
-transparent to allow sunlight to penetrate to mesophyll layers

Question 10

upper and lower epidermis

Answer 10

-single layer of closely packed cells, no chloroplasts
-protect the leaves from mechanical damage

Question 11

stomata

Answer 11

-small openings, surrounded by guard cells (that contain chloroplasts) which regulate stomata sizes affecting the rate of diffusion of gases

Question 12

palisade mesophyll

Answer 12

-one layer of closely packed long and cylindrical cells which contain numerous chloroplasts for maximum light energy absorption by chlorophyll

Question 13

spongy mesophyll

Answer 13

-irregularly shaped cells with large intercellular air spaces
-this facilitates rapid diffusion of carbon dioxide to be absorbed into mesophyll cells for photosynthesis
-fewer chloroplasts than palisade mesophyll

Question 14

when there is sunlight,

Answer 14

-chloroplasts in guard cells perform photosynthesis to produce glucose
-hence, water potential is lowered in the cell sap
-cell sap absorb water molecules from surrounding cells by osmosis across selectively permeable membrane
-thus, guard cells become turgid, stoma size increases

Question 15

when there is no sunlight,

Answer 15

-no photosynthesis occurs in chloroplasts of guard cells, no glucose produced
-water potential in guard cell sap is less negative than surrounding cells
-cell sap loses water molecules to surrounding cells by osmosis across selectively permeable membrane
-thus, guard cells become flaccid, stoma size decreases