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Erschienen in:
2019 | OriginalPaper | Buchkapitel
Biomass Production: Biological Basics
verfasst von : Matthias Gilbert, Christian Wilhelm
Erschienen in: Energy from Organic Materials (Biomass)
Verlag: Springer New York
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Excerpt
C3 plants
Plants using ribulose-1,5-bisphosphate-carboxylase/−oxygenase (Rubisco) as primary carboxylation enzyme to transfer CO2 on ribulose-1,5-bisphosphate to form in a first step 3-phosphoglycerate (2 × C-3). Part of the assimilated carbon is lost in C3 plants by photorespiration due to a lower CO2 concentration at the site of Rubisco than in C4 plants.
C4 plants
Plants using phosphoenol-pyruvate-(PEP)-carboxylase as primary carboxylation enzyme to transfer CO2 on PEP to form in a first step malate (C-4). Malate is transported to the bundle sheath cells (Kranz anatomy) to be decarboxylated at the site of Rubisco resulting in a high CO2 concentration and in turn very low or absent photorespiration.
Crassulacean acid metabolism (CAM) plants
Plants also using phosphoenol-pyruvate carboxylase as primary carboxylase. They fix CO2 preferentially during the night as malate that is stored in the vacuole. During the day malate is decarboxylated at the site of Rubisco resulting in high CO2 concentration and very low or absent photorespiration. Since CAM plants can keep their stomata closed during the day, they have very low transpiration rates and can survive extreme drought stress.
Harvest index
In food crops the ratio of grain yield to total plant biomass. More general, the amount of total biomass/bioenergy partitioned into the harvested portion of the crop.
Marker assisted selection (MAS)
A method in plant breeding. Screening of plant samples based on a DNA marker (sequence) linked to a trait of interest (e.g., aboveground biomass).
Net primary production (NPP)
The annual accumulation of plant organic matter per unit of land (g m−2 year−1). Net primary production (NPP) is gross primary production minus plant respiration and photorespiration. Since plant tissue typically contains about 50% carbon, division of NPP by two converts NPP to a measure of carbon fixation.
Photorespiration
Due to the dual function of ribulose-1,5-bisphosphate-carboxylase/−oxygenase (Rubisco) being a carboxylase and an oxygenase also molecular oxygen can be transferred on ribulose-1,5-bisphosphate, when CO2 concentrations are low. In a complex side reaction, the cleaved compound phosphoglycolate is decarboxylated by liberation of CO2 (“respiration in the light” = photorespiration). Photorespiration is accompanied by a net loss of carbon and results in a reduction of photosynthetic efficiency and is typical for C3 plants.
Photosynthetic efficiency
Efficiency with that photosynthesis can convert intercepted solar energy into chemical energy like carbohydrates or biomass. It is defined by the ratio of stored chemical energy to intercepted solar energy over a given time.
Plant biomass/bioenergy crops
Biomass, amount of material (fresh weight or dry weight) from living or recently living plants; bioenergy crops, plants used for biomass harvest utilized for bioenergy/biofuel production.
Water use efficiency
Ratio of CO2 assimilation or dry weight (DW) yield per unit transpired water.