C1.3 - limiting factors of photosynthesis (4c) Flashcards
what are the 3 limiting factors of photosynthesis?
- temperature
- carbon dioxide concentration
- light intensity
what is a limiting factor?
the factor that is nearest to its minimum, and so limits the rate of reaction
how is temperature a limiting factor for photosynthesis?
photosynthesis is a metabolic reaction and is therefore controlled by enzymes
- higher temperatures increase enzyme activity, because there is more molecular kinetic energy, so faster molecular motion, leading to more frequent enzyme-substrate collisions.
- however, if the temperature exceeds the optimum for the essential enzymes of photosynthesis, they denature and the rate of photosynthesis falls.
how is light intensity a limiting factor for photoysnthesis?
higher light intensity increases the rate of photosynthesis
- this is because light is the source of energy for photosynthesis, with light energy being converted to chemical energy.
- at high intensities of light the rate of photosynthesis plateaus, because another factor has become limiting
how is carbon dioxide concentration a limiting factor for photosynthesis?
higher carbon dioxide concentration increases the rate of photosynthesis
- this is because carbon dioxide is a reactant and is fixed to form glucose and other organic molecules
- at high concentrations of carbon dioxide, the rate of photosynthesis plateaus and another factor has become limiting
what are hypotheses?
provisional explanations that require repeated testing
what can hypotheses be based on?
during scientific research, hypotheses can be either bases on:
- theories and then tested in an experiment
- evidence from an experiment that has already been carried out
what are possible methods to investigate the effects of limiting factors on photosynthesis (dependent variable)?
- counting bubbles or measuring the volume of oxygen releases by aquatic plants per unit time
- using pH indicators or sensors, with aquatic plants or algae, to measure the decrease in acidity over time, as plants consume carbon dioxide from the water
- using electronic sensors to measure the concentration of carbon dioxide or oxygen, in aquatic settings and closely-controlled terrestrial settings
how can we investigate light intensity as an independent variable?
- use different power bulbs
- changes the distance between plants and light source
how can we investigate temperature as an independent variable?
use water baths to change the temperature of the water
how can we investigate carbon dioxide concentration as an independent variable?
adding different concentrations of sodium hydrogen carbonate
what are possible control variables used to investigate the effects of limiting factors on photosynthesis?
- plant species
- plant mass/length
- length of incubation time
- equilibrium time
what is the relationship between photosynthesis and carbon dioxide concentration in the atmosphere?
it has been verified that increases carbon dioxide concentration in the atmosphere increases the rate of photosynthesis and plant growth
what are the 2 types of carbon dioxide enrichment experiments?
- enclosed greenhouse experiments involve growing plants within a greenhouse whose atmosphere has added carbon dioxide
- free-air carbon dioxide enrichment experiments (FACE) are studies in natural settings, where the conditions cannot be controlled as they can in laboratories or greenhouses
what are strengths of both types of carbon dioxide enrichment experiences?
- FACE involve artificially increasing carbon dioxide levels in natural and agricultural ecosystems and gives a more valid picture of what might happen in the future, compared to laboratory or greenhouse investigations
- enclosed greenhouse experiments are easier to control variables, improving validity of this method
