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Use of the response of photosynthesis to oxygen to estimate mesophyll conductance to carbon dioxide in water‐stressed soybean leaves
Author(s) -
BUNCE JAMES A.
Publication year - 2009
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2009.01966.x
Subject(s) - carbon dioxide , photosynthesis , stomatal conductance , oxygen , conductance , agronomy , environmental science , carbon dioxide in earth's atmosphere , botany , chemistry , biology , ecology , mathematics , organic chemistry , combinatorics
Methods of estimating the mesophyll conductance (g m ) to the movement of CO 2 from the substomatal airspace to the site of fixation are expensive or rely upon numerous assumptions. It is proposed that, for C 3 species, measurement of the response of photosynthesis to [O 2 ] at limiting [CO 2 ], combined with a standard biochemical model of photosynthesis, can provide an estimate of g m . This method was used to determine whether g m changed with [CO 2 ] and with water stress in soybean leaves. The value of g m estimated using the O 2 response method agreed with values obtained using other methods. The g m was unchanged over the tested range of substomatal [CO 2 ]. Water stress, which decreased stomatal conductance (g s ) by about 80%, did not affect g m , while the model parameter V Cmax was reduced by about 25%. Leaves with g s reduced by about 90% had g m values reduced by about 50%, while V Cmax was reduced by about 64%. It is concluded that g m in C 3 species can be conveniently estimated using the response of photosynthesis to [O 2 ] at limiting [CO 2 ], and that g m in soybean was much less sensitive to water stress than g s , and was somewhat less sensitive to water stress than V Cmax .