Spatial and seasonal variations in photosynthetic properties within a beech (Fagus crenata Blume) crown |
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Authors: | Hideyuki Saito Yoshitaka Kakubari |
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Institution: | (1) Faculty of Agriculture, University of Shizuoka, 422-8529 Shizuoka, Japan |
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Abstract: | The light response curve and the intercellular CO2 concentration response curve of CO2 assimilation rate were investigated together with the light conditions at the four different heights within the beech crown
from 1995 to 1997 on Mt. Fuji in Japan. On the seasonal fluctuation, the CO2 assimilation rate at light saturated condition increased rapidly in May, and attained to the maximum between the end of June
and July, thereafter, slightly decreased until the middle of August and rapidly decreased in September and October. The daily
sum of photosynthetic photon flux density attenuated with deeping within the crown, and particularly, the relative value on
2nd position dropped to only 30%. TheA
max decreased from 10 to 5μmol m−2 s−1, approximately, with deeping within the crown. The light saturation point, quantum yield, light compensation point and dark
respiration rate also varied with deeping. These results suggest that the photosynthetic properties vary gradually from sun
to shade leaves along the light attenuation within a beech crown. At light saturated condition, the stomatal conductance and
mesophyll conductance were strongly correlated withA
max among the four different heights (r > 0.96, respectively). TheC
i/C
a ratio was around 0.8, and there were no remarkable differences among the four different heights. These results suggest that
the vertical gradient ofA
max depends on the variation of mesophyll conductance. The stomatal conductance may be also one of the major factor in the vertical
gradient ofA
max. However the intercellular CO2 concentration doesn’t influence the vertical gradient ofA
max within the crown.
This work is supported by the Sasagawa Scientific Research Grant from The Japan Science Society and Grant-in-Aid for Scientific
Research (C). |
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Keywords: | CO2 assimilation light conditions mesophyll conductance Siebold’ s beech (Fagus crenata Bl ) crown stomatal conductance |
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