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Photosynthesis in green pepper fruits

Marian Czarnowski

The Franciszek Górski Department of Plant Physiology
Polish Academy of Sciences
Sławkowska 17, 31-016 Kraków, Poland

It was found that the CO2 evolution rate from young green pepper fruits reached an average level of -1.62 μmol(CO2) kg-1 (d.m.) s-1 and -0.77 μmol(CO2) kg-1 (d.m.) s-1 from older ones in darkness. Under irradiance of 800 μmol(quantum) m-2 s-1 PAR it was -0.65 and -0.16 μmol(CO2) kg-1 (d.m.) s-1 respectively. The photosynthetic rate in young fruits amounted to 0.97 μmol(CO2) kg-1 (d.m.) s-1 and 0.36 μmol(CO2) m-2 s-1 calculated per surface unit but 0.61 μmol(CO2) kg-1 (d.m.) s-1 and 0.23 μmol(CO2) m-2 s-1 respectively in older ones. For comparison, the net photosynthetic rate in pepper leaves reached a value of 9.7 μmol(CO2) m-2 s-1. Therefore the photosynthetic rate in young green pepper fruits was about 4% and in older ones about 2.4% of the rate in leaves of the same cultivar.

The photosynthetic process in green pepper fruits occurred below the CO2 compensation level and thus did not counterbalance the ednogenous CO2 sources. Owing to the high internal CO2 concentration, amounting to 3000 μmol(CO2) mol-1 of air in green pepper fruits even under optimal irradiance, CO2 diffusion always proceeded in one direction, i.e. from the fruits to the environment. The photosynthesis in the green pepper fruits, which although not of essential importance in the production of biomass, considerably reduces the loss of assimilates necessary for respiration (about 60% in young fruits and about 80% in older ones).

Czarnowski M., 1995. Photosynthesis in green pepper fruits. Folia Horticulturae 7/1: 37-47.