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An examination of the advantages of C 3 ‐C 4 intermediate photosynthesis in warm environments
Author(s) -
SCHUSTER W. S.,
MONSON R. K.
Publication year - 1990
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.1365-3040.1990.tb01980.x
Subject(s) - photorespiration , photosynthesis , c4 photosynthesis , vascular bundle , botany , biology , nitrogen , horticulture , chemistry , organic chemistry
. The photosynthetic responses to temperature in C 3 , C 3 ‐C 4 intermediate, and C 4 species in the genus Flaveria were examined in an effort to identify whether the reduced photorespiration rates characteristic of C 3 ‐C 4 intermediate photosynthesis result in adaptive advantages at warm leaf temperatures. Reduced photorespiration rates were reflected in lower CO 2 compensation points at all temperatures examined in the C 3 ‐C 4 intermediate, Flaveria floridana , compared to the C 3 species, F. cronquistii . The C 3 ‐C 4 intermediate, F. floridana , exhibited a C 3 ‐like photosynthetic temperature dependence, except for relatively higher photosynthesis rates at warm leaf temperatures compared to the C 3 species, F. cronquistii . Using models of C 3 and C 3 ‐C 4 intermediate photosynthesis, it was predicted that by recycling photorespired CO 2 in bundle‐sheath cells, as occurs in many C 3 ‐C 4 intermediates, photosynthesis rates at 35°C could be increased by 28%, compared to a C 3 plant. Without recycling photorespired CO 2 , it was calculated that in order to improve photosynthesis rates at 35°C by this amount in C 3 plants, (1) intercellular CO 2 partial pressures would have to be increased from 25 to 31 Pa, resulting in a 57% decrease in water‐use efficiency, or (2) the activity of RuBP carboxylase would have to be increased by 32%, resulting in a 22% decrease in nitrogen‐use efficiency. In addition to the recycling of photorespired CO 2 , leaves of F. floridana appear to effectively concentrate CO 2 at the active site of RuBP carboxylase, increasing the apparent carboxylation efficiency per unit of in vitro RuBP carboxylase activity. The CO 2 ‐concentrating activity also appears to reduce the temperature sensitivity of the carboxylation efficiency in F. floridana compared to F. cronquistii . The carboxylation efficiency per unit of RuBP carboxylase activity decreased by only 38% in F. floridana , compared to 50% in F. cronquistii , as leaf temperature was raised from 25 to 35°C. The C 3 ‐C 4 intermediate, F. ramosissima , exhibited a photosynthetic temperature temperature response curve that was more similar to the C 4 species, F. trinervia , than the C 3 species, F. cronquistii . The C 4 ‐like pattern is probably related to the advanced nature of C 4 ‐like biochemical traits in F. ramosissima The results demonstrate that reductions in photorespiration rates in C 3 ‐C 4 intermediate plants create photosynthetic advantages at warm leaf temperatures that in C 3 plants could only be achieved through substantial costs to water‐use efficiency and/or nitrogen‐use efficiency.