Preliminary Course.
Eco-Physiology
Photosynthesis.
Growth & Maintenance respiration
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Plant functioning corresponds to growth and maintenance of the living
structure.
Taking into account environmental factors, biomass production at the level of square metres per unit of time is summarized by the following equation:
- dW/dt = Yg ( Pg - Rm )
where
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Pg is gross photosynthesis,
Rm is the cost of structure maintenance,
Yg is growth conversion efficiency,
and dW/dt is biomass production in the crop per square metre per unit of time.
Rm is assumed to have priority over growth
If Rm > Pg then Rm is set equal to Pg and biomass production is thus zero.
Yg, growth conversion efficiency, depends on the chemical composition; it stands for the costs of converting sugars into fats, organic acids, etc.
Typical values for Yg are 0.35 for oil-rich seeds, 0.6 for leaves and stem, up to 0.8 for the root of sugar beet.
Note that under stress conditions (e.g., soil salinity), the main share of sugars is used to fight against osmotic stress and thus the growth process can be greatly reduced.