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Mindmap von harry_bygraves, aktualisiert more than 1 year ago
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Factors limiting the rate of photosynthesis
- Measuring the rate of photosynthesis; can be estimated
from, the volume of oxygen released by a plant, the
volume of carbon dioxide taken in by the plant per unit
time, the amount of carbohydrate produced by unit time
- Using oxygen liberation underestimates the true rate of photosynthesis. What is
actually being measured is the rate of photosynthesis above a point called the
compensation point. This is defined as the point at which the rate of
photosynthesis in a plant is in exact balance with thte rate of respiration, so there
isno net exchange of carbon dioxide or oxygen
- Temperature; changes in temperature have little effect on
the reactions of the light-dependant stage because these are
driven by light, not heat. However, the reactions of the calvin
cycle are catalysed by enzymes which, like all enzymes, are
sensitive to temperature. The effect of temperature on these
reactions is similar ti its effects on other enzymes
- Carbon dioxide levels; the average carbon dioxide content of the atmosphere is about 0.04%. An increase
up to 0.5% usually results in an increase in the rate of photosynthesis. However, Concentrations above
0.1% can dmaage leaves. Therefore the optimum comcentration of carbon dioxide is probably just under
0.1%. In dense, warm, and well lit vegetation, low levels of carbon dioxide often limit the rate of
photosynthesis.
- Light intensity; the rate of photosynthesis is directly proportional to light intensity up to a
maximum point after which the rate of levels off because the photosynthetic pigments
have become saturated with light. Very high light intensities may actually damage some
plants, reducing the ability to photosynthesize. The light compensation point; the light
intensity at which the rate of photosynthesis is exactly balanced by the rate of respiration
- The principle limiting factors; states that when a physiological process such as
photosynthesis depends on more than one essesntial factor being favourable,
its rate at any given moment is limited by the factor at its least favourable value
and by that factor alone. This factor is called the limiting factor
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