photosynthesis rate limiting factors

Question 1

list the 6 conditions needed for photosynthesis

Answer 1

carbon dioxide – diffuses into leaves from air via stoma
water - absorbed from soil by roots (xylem)
sunlight energy – absorbed by chlorophyll in chloroplasts in palisade and spongy layer in leaf
chlorophyll – the green pigment present in chloroplasts
enzymes – present in chloroplasts
suitable temperature between 5 and 40 so enzymes can function

Question 2

define rate limiting factor

Answer 2

factor that limits rate of a reaction
usually one in the least quantity

Question 3

list 4 factors which affect the rate of photosynthesis

Answer 3

light – limits between dusk and dawn and also during winter months in temperate climates
temperature – limits during winter months in temperate climates
water – limits during the dry season in tropical climates and when the ground is frozen in temperature
carbon dioxide – limits during day in most climates since concentration of CO2 in the air is low (0.04%)

Question 4

what is the fate of glucose produced in photosynthesis

Answer 4

used in respiration to make energy
stored in leaf cells as starch
converted into other organic substances such as amino acids proteins vitamins chlorophyll
converted to sucrose and transpored via phloem to other parts of plant sucrose then converted into glucose (respiration) cellulose (cell walls) starch (stored) amino acids and proteins (nitrogen added growth ) lipids (stored eg seeds )

Question 5

when is carbon dioxide usually the limiting factor

Answer 5

when temperature and light levels are high
greenhouses often pump in extra carbon dioxide to increase rate of photosynthesis in crops

Question 6

define the availability of water

Answer 6

varies in the environment
if soil is dry water may be limiting factor on photosynthsis

Question 7

explain etiolation

Answer 7

if a plant cannot get sunlight it cannot photosynthesise and therefore cannot make food
however this does not mean it cannot grow
for a short while it can use some of the food stored within the plant to grow and lengthen
this gives it a chance to get some leaves into the light and so start to photosynthesise again
since all energy is used to make long thin cells the stem becomes elongated and thin and leaves kept very small
stems and leaves are pale yellow since no chlorophyll is made