PRINCIPAL 



INVESTIGATOR(S) Richard J. Geider 



College of Marine Studies 



University of Delaware 



Lewes, DE 19958 



PROJECT TITLE CONTROL OF LIGHT SATURATED PHOTOSYNTHESIS BY 



THE CONCENTRATION AND ACTIVITY OF RIBULOSE 

 BISPHOSPHATE CARBOXYLASE 



AMOUNT OF FUNDING FY 1994: $85 K 



SUMMARY OF GOALS 



The primary objective is to determine whether the maximum, light- saturated rate of 

 photosynthesis (Pm) of phytoplankton can be predicted from measurements of the concentration 

 and catalytic activity of ribulose bisphosphate carboxylase. Specifically, we seek to determine 

 the extent of variability in the maximum catalytic rate, the activation state and the ratio of 

 Rubiscoxhlorophyll a in marine phytoplankton. Variations in activation state of rubisco may 

 result from physiological adaptation, light-activation, diel rhythms and interspecific (genetic) 

 variability. 



SPATIAL AND TEMPORAL SAMPLING SCALES 



The appropriate time scales for sampling are those on which Pm varies. Processes which 

 modulate Pm operate on time scales of hours (diel variability in Pm) and days (physiological 

 adaptation). Thus, we wish to investigate within day and between day variability. 



We require, at a minimum, morning, midday and evening samples from the top and 

 bottom of the mixed layer and from the chlorophyll maximum layer (if there is one). We would 

 like to sit on station to minimize spatial variability in process studies examining diel variability, 

 but can accommodate spatial variability in surveys (if necessary, we can conduct studies of diel 

 variability using samples incubated in controlled temperature deck top incubators). 



It is imperative that this research be conducted in conjunction with fast repetition rate 

 fluorescence investigations. FRR and Rubisco measurements provide complementary 

 information. One goal of this research is to assess the relationship between regulation of the 

 turnover time of whole chain electron flow and the regulation of rubisco activity. 



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