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Photosynthetic Responses of ‘Bragg’ Soybean Leaves Adapted to Different CO 2 Environments 1
Author(s) -
Valle Raul,
Mishoe J. W.,
Campbell W. J.,
Jones J. W.,
Allen L. H.
Publication year - 1985
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1985.0011183x002500020030x
Subject(s) - photorespiration , photosynthesis , compensation point , carbon dioxide , biology , botany , horticulture , acclimatization , zoology , analytical chemistry (journal) , chemistry , transpiration , environmental chemistry , ecology
Carbon dioxide exchange rates (CER) were measured during seed fill on leaflets of soybean [ Glycine max (L.) Merr. ‘Bragg’] plants grown at 330 and 660 μmol mol −1 CO 2 environments in outdoor growth chambers to investigate their photosynthetic response to light. During midday periods at the R5 growth stage, the plants were submitted to short‐term CO 2 levels ranging from 90 to 990 μmol mo1 −1 to determine differences in leaf photosynthetic response caused by CO 2 acclimation. The data were fitted to a rectangular hyperbola of the Michaelis‐Menten form in which the independent variable was radiation or CO 2 . Light and CO 2 compensation points were calculated from the parameters of the model. Light response curves showed that leaflets grown and measured at 660 μmol mol −1 CO 2 had higher CER asymptotes, higher apparent Michaelis‐Menten constants for light, higher apparent quantum yield, and lower light compensation points than leaflets adapted to and measured at 330 μmol mol −1 CO 2 . The CER‐CO 2 curve parameters also indicated higher asymptotic ceilings of CER at high CO 2 and higher apparent Michaelis‐ Menten constants for CO 2 for the higher CO 2 adapted leaflets. The CO 2 compensation point was significantly lower in leaflets adapted to high CO 2 levels than those adapted to ambient CO 2 , indicating a decrease in photorespiration. It was concluded that, during seed fill, leaflets adapted to high CO 2 environments exhibited a capability to utilize CO 2 and radiation more efficiently at elevated CO 2 and throughout all light levels than leaflets grown at low CO 2 .