Factors AffectingPhotosynthesis

Question 1

What is a limiting factor?

Answer 1

In metabolic processes it is the factor that is present at the lowest it least favourable value

Question 2

What effect does carbon dioxide concentration have on rate of photosynthesis?

Answer 2

Co2 fixed in Calvin cycle, enhances levels of CO2 will increase rate of photosynthesis, providing there is no other limiting factor

Question 3

What if the effect of light intensity on photosynthesis?

Answer 3

As light intensity increases, rate of photosynthesis increases, opens stomata for more co2 entrance, trapped by chlorophyll, splits water molecules (only split in presence of light), electrons and protons involved in photophosphorylation, producing ATP for fixation of co2

Question 4

What is the effect of temperature on rate of photosynthesis?

Answer 4

Photochemical reactions in light dependent not affected much, enzyme reactions in LI increase activity with temp, but if too high rate levels off and falls as enzymes denature and oxygen competes successfully for rubisco, more water loss from stomata, so they close, so less CO2 available

Question 5

How does reduced light intensity affect rate if light independent stage?

Answer 5

Less ATP and reduced NADP produced, so GP not reduced to TP and accumulates, less RuBP as is not regenerated

Question 6

How can you measure rate of photosynthesis?

Answer 6

Measure volume of oxygen produced
Rate of uptake of CO2
Rate of increased dry mass in plants

Question 7

What are limitations of using oxygen to measure rate?

Answer 7

Some oxygen used in respiration

Dissolved nitrogen may be in has collected

Question 8

How can you investigate effect of light intensity on rate of photosynthesis?

Answer 8

Use photosynthometer, must be airtight, gas given off by plant collected as bubble in capillary tube, length can be measured and converted to volume = length x pir2
Water bath used to keep constant temperature, sodium hydrogen carbonate added do carbon dioxide not limiting, only light a kibble from light soutce, so in dark room, low energy so doesn’t release much heat

Question 9

What is a photosynthometer?

Answer 9

Used to measure rate of photosynthesis by collecting and measuring the volume of oxygen produced in a certain time

Question 10

What is formula for light intensity?

Answer 10

L=1/d2(distance)

Question 11

What are limitations of investigating light? P

Answer 11

Fluctuation in temperature, ambient light, timing, not pure oxygen

Question 12

How can temperature affecting rate be investigated?

Answer 12

All other factors constant. Light intensity with high rate used, temperature controlled by water bath, measure volume of gas produced in set time

Question 13

How can carbon dioxide affecting rate be measured?

Answer 13

Keep all other factors constant, vary amount of Na hco3 added, measure vol of gas produced

Question 14

How can rate of photosynthesis be measure using changes in density of leaf disc

Answer 14

Cut seeds-cotyledons- place in hydrogen carbonate solution, use syringe to pull air out if air spaces in leaf discs, replaced by Na hco3 solution, density increases so they sink. Transfer to water, time how long it takes for leaf disc to float under different conditions. Leaves photosynthesis and make oxygen do float

Question 15

How does light intensity limit the Calvin cycle?

Answer 15

Affects rate of light dependent reaction, if little or no light, LD ceases, so LI stops as needs products of light dependent to run, GP accumulates, no TP l, less RuBP

Question 16

How does carbon dioxide concentration affect Calvin cycle?

Answer 16

Carbon dioxide for carbon fixation, more co2 is increased rate, however stomata open leads to more transpiration, so plant may wily if water uptake cannot exceed loss, so stomata close, less co2 uptake. If carbon dioxide concentration reduced, RuBP accumulates and level of GP and TP falls

Question 17

What affect does temperature have on Calvin cycle?

Answer 17

Alter rate as relies on enzymes, increasing increses rate, too high and enzymes will denature, increases water kids from transpiration, so less co2 as stomata close, more oxygen saw activity of rubisco, so more photorespiration, Calvin cycle cannot occur, light dependent products wasted, reduces rate of photosynthesis

Question 18

How does lack of magnesium affect rate?

Answer 18

Less chlorophyll, so fewer photosystems