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SUMMARY:Modeling adaptive response of starch metabolism to various photope
 riods - Akiko Sakate\, Hokkaido University
DTSTART:20130220T130000Z
DTEND:20130220T140000Z
UID:TALK43650@talks.cam.ac.uk
CONTACT:31151
DESCRIPTION:Although photosynthetic carbon assimilation occurs only in the
  light\, growth and respiration requiring carbon also occur in the dark. S
 tarch reserve enables this continuous growth throughout the day-night cycl
 e. Starch is stored during the day inside chloroplasts and broken down at 
 night to provide sugars to sinks\, allowing metabolism and growth regardle
 ss of light or dark. Previous studies have reported that starch is accumul
 ated and is degraded almost linearly\, rather than exponentially\, drawing
  a pyramid shape in the day-night cycle. More interestingly\, the shape of
  pyramid adaptively changes in response to the various length of light per
 iod. Here we propose a model of adaptive starch metabolism in response to 
 changing photoperiod. We assume key metabolic rates\, carbon partitioning\
 , starch degradation\, and sucrose export\, to be circadian regulated in l
 eaves and their phases of oscillation are shifted in response to sucrose s
 tarvation. We performed gradient descents for various photoperiod conditio
 ns to find the corresponding optimal sets of phase shifts that minimize st
 arvation best. Results at convergence were all consistent with experimenta
 l data: i) diurnal starch profile showed linear increase during the day an
 d linear decrease at night\; ii) reducing light period tended to increase 
 starch synthesis speed during the shorter day while decreasing its degrada
 tion speed during the longer night\; iii) sudden early dusk showed slower 
 starch degradation during the longer night. This theoretical study would e
 stablish a framework for future research on starch and plant productivity.
LOCATION:Tom ap Rees\, Department of Plant Sciences
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