Tominaga, Jun and Kawasaki, Syunichiro and Yabuta, Shin and Fukuzawa, Yasunori and Suwa, Ryuichi and Kawamitsu, Yoshinobu
(2010)
Eclipse effects on CO2 profile within and above sorghum canopy.
Plant Production Science, 13 (4).
pp. 338-346.
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Abstract
We analyzed the effects of a partial solar eclipse (22 July 2009) on microclimate including
vertical gradients of CO2 concentrations ([CO2]), so called [CO2] profile, in a mature sorghum
canopy. Together with CO2 measurement, major photosynthetic drivers of microclimate, light
intensity, temperature and atmospheric H2O concentration ([H2O]) were also measured
simultaneously at the same place and height. [CO2] at 6.0, 3.2, 2.1, 1.4, 0.7, 0 m above the ground
(canopy height was 3.2 m) increased by 5.8, 4.8, 9.0, 7.8, 6.4, 7.6μmol mol-1, respectively, from 1
hour before the eclipse maximum to the eclipse maximum, during which the incident solar
radiation above the canopy dropped by 1473 μmol photons m-2 s-1. However, it declined by 3.4,
10.6, 10.8, 6.0, 5.4, and 5.8μmol mol-1, respectively, from the eclipse to 1 hour later, during which
the incident radiation increased by 1350μmol photons m-2 s-1. The [CO2] profi le during the eclipse
was uniform except for higher [CO2] near the ground. Comparative analysis of the effect of light
intensity on the microclimate during the eclipse-induced light decreasing phase (ELDP) and
eclipse-induced light increasing phase (ELIP) revealed that [CO2], [H2O], temperature and relative
humidity (RH) are significantly correlated with the light intensity above the canopy in a nearly
linear fashion. Furthermore it indicated that detected less light-reacted canopy photosynthesis at a
higher layer within the canopy during ELIP might be due to slower response of stomatal opening
(than closing) to the light intensity above the canopy.
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