Effects of seasonal change and experimental warming on the temperature dependence of photosynthesis in the canopy leaves of Quercus serrata.
The effects of warming on the temperature response of leaf photosynthesis have become an area of major concern in recent decades. Although growth temperature (GT) and day length (DL) affect leaf gas exchange characteristics, the way in which these factors influence the temperature dependence of photosynthesis remains uncertain. We established open-top canopy chambers at the canopy top of a deciduous forest, in which average daytime leaf temperature was increased by 1.0 °C. We conducted gas exchange measurements for the canopy leaves of deciduous trees exposed to artificial warming during different seasons. The carbon dioxide assimilation rate at 20 °C (A20) was not affected by warming, whereas that at 25 °C (A25) tended to be higher in leaves exposed to warming. Warming increased the optimal temperature of photosynthesis by increasing the activation energy for the maximum rate of carboxylation. Regression analysis indicated that both GT and DL strongly influenced gas exchange characteristics. Sensitivity analysis revealed that DL affected A without obvious effects on the temperature dependence of A, whereas GT almost maintained constant A20and strongly influenced the temperature dependence. These results indicate that GT and DL have different influences on photosynthesis; GT and DL affect the 'slope' and intercept' of the temperature dependence of photosynthesis, respectively.
Graduate School of Life Sciences, Tohoku University, Aoba, Sendai, 980-8578 Miyagi, Japan yamaguchi9876@gmail.com.
Daisuke P
DP
Yamaguchi
Tomakomai Research Station, Field Science Center for Northern Biosphere, Hokkaido University, Tomakomai, 053-0035 Hokkaido, Japan.
Tatsuro
T
Nakaji
Tomakomai Research Station, Field Science Center for Northern Biosphere, Hokkaido University, Tomakomai, 053-0035 Hokkaido, Japan.
Tsutom
T
Hiura
Graduate School of Life Sciences, Tohoku University, Aoba, Sendai, 980-8578 Miyagi, Japan.|CREST, Japan Science and Technology Agency (JST), 102-0076 Tokyo, Japan.
Kouki
K
Hikosaka
D002245:Carbon Dioxide / Q000378:metabolism; D057232:Global Warming; D010788:Photosynthesis; D018515:Plant Leaves / Q000502:physiology; D029963:Quercus / Q000502:physiology*; D012621:Seasons; D013696:Temperature
D002245:Carbon Dioxide
Vcmax; activation energy; day length; optimal temperature of photosynthesis; simulation; temperature acclimation