Corresponding to IGCSE Edexcel Pearson Biology specification (information likely to apply to/cover other exam boards).
Highly detailed notes, includes step-by-step methods and examples (where helpful to topic) and annotated diagrams.
Feature controlled How it is controlled Reason for controlling
Light intensity and duration
Using lamps, windows etc... Light intensity is essential for catalysing
photosynthesis, so must be sufficient and
constant during the daytime. Higher light
intention = higher rate of photosynthesis. This
means that light intensity will not be the
limiting factor.
Carbon dioxide concentration
Burn fossil fuels inside the greenhouse/tunnel using a gas Carbon dioxide is needed as a reactant for
heater. (This also controls arid flow which increases photosynthesis, so must be sufficient and
humidity). constant. Higher concentration = more
respiration. This means that carbon dioxide
concentration will not be the limiting factor.
Temperature
Burn fossil fuels inside the greenhouse/tunnel using a gas Must be controlled to be at an optimum
heater. temperature for enzymes to work but the plant
is not having to cool itself via transpiration.
This means that, at optimum, temperature will
not be the limiting factor.
Mineral content of the soil
Lime or calcium salts added to soil to reduce pH if needed. Mineral ions are essential for growth.
Magnesium and nitrate ions are essential. Magnesium is essential for producing
chlorophyll. Nitrate is needed to provide
nitrogen for the production of amino acids and
then protein synthesis, essential for growth.
Competition from weeds
Weed killer, regular tending etc.. Weeds will compete with the plant for
resources. This reduces the minerals, water and
carbon dioxide available to the plant. This may
hinder their growth or render them unable to
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