Morphological and photosynthetic responses of Quercus crispula seedlings to high-light conditions.
We investigated morphological and photosynthetic responses of current-year seedlings of oak (Quercus crispula Blume) under high-light conditions. Quercus crispula seedlings were grown from seed in a relative photosynthetically active photon flux density (RPPFD) of 100, 10 or 2%. There was no difference in total dry mass between 100 and 10% RPPFD. At the end of the growing season, plants grown in 2% RPPFD had a lower total dry mass than those grown in 100 or 10% RPPFD. Seedlings grown in 100% RPPFD showed morphological acclimation, i.e., high root/shoot ratios and high leaf mass per area. De-epoxidation level in the xanthophyll cycle and activity of an antioxidant enzyme were highest in 100% RPPFD, but total chlorophyll concentration and photosynthetic rate were highest in 10% RPPFD. These results indicate that excess photons were generated in 100% RPPFD, leading to increased capacities for dissipation of received light energy through the xanthophyll cycle and for scavenging of reactive oxygen species through the water-water cycle. Nevertheless, a midday decrease in dark-adapted quantum yield of photosystem II (F(v)/F(m)) indicated that seedlings grown in 100% RPPFD were suffering from photoinhibition. We conclude that Q. crispula current-year seedlings have high morphological acclimation to high light but that photosynthetic efficiency cannot be maintained under high-light conditions even with a photoprotection system.
Matsuki
Sawako
S
Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819, Japan. s-matsuk@exfor.agr.hokudai.ac.jp
Ogawa
Ken'ichi
K
Tanaka
Ayumi
A
Hara
Toshihiko
T
D002734:Chlorophyll / Q000502:physiology; D008027:Light; D010788:Photosynthesis / Q000502:physiology*; D029963:Quercus / Q000033:anatomy & histology / Q000502:physiology*; D012621:Seasons; D036226:Seedlings / Q000033:anatomy & histology / Q000502:physiology*; D014197:Trees / Q000033:anatomy & histology / Q000502:physiology*; D024341:Xanthophylls / Q000502:physiology
D024341:Xanthophylls; D002734:Chlorophyll