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Mesophyll conductance does not contribute to greater photosynthetic rate per unit nitrogen in temperate compared with tropical evergreen wet‐forest tree leaves
Author(s) -
Bahar Nur H. A.,
Hayes Lucy,
Scafaro Andrew P.,
Atkin Owen K.,
Evans John R.
Publication year - 2018
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.15031
Subject(s) - evergreen , stomatal conductance , photosynthesis , temperate climate , temperate forest , evergreen forest , botany , environmental science , biology , nitrogen , ecophysiology , tropical forest , temperate rainforest , agronomy , ecology , chemistry , ecosystem , organic chemistry
Summary Globally, trees originating from high‐rainfall tropical regions typically exhibit lower rates of light‐saturated net CO 2 assimilation ( A ) compared with those from high‐rainfall temperate environments, when measured at a common temperature. One factor that has been suggested to contribute towards lower rates of A is lower mesophyll conductance. Using a combination of leaf gas exchange and carbon isotope discrimination measurements, we estimated mesophyll conductance ( g m ) of several Australian tropical and temperate wet‐forest trees, grown in a common environment. Maximum Rubisco carboxylation capacity, V cmax , was obtained from CO 2 response curves. g m and the drawdown of CO 2 across the mesophyll were both relatively constant. V cmax estimated on the basis of intercellular CO 2 partial pressure, C i , was equivalent to that estimated using chloroplastic CO 2 partial pressure, C c , using ‘apparent’ and ‘true’ Rubisco Michaelis–Menten constants, respectively Having ruled out g m as a possible factor in distorting variations in A between these tropical and temperate trees, attention now needs to be focused on obtaining more detailed information about Rubisco in these species.