This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Web of Science (25) Citing Articles via Google Scholar Google Scholar Articles by Usuda, H. Articles by Huber, S. C. Search for Related Content PubMed PubMed Citation Articles by Usuda, H. Articles by Huber, S. C. Agricola Articles by Usuda, H. Articles by Huber, S. C.

Metabolism and Enzymology

Diurnal Changes in Maize Leaf Photosynthesis ¹

II. Levels of Metabolic Intermediates of Sucrose Synthesis and the Regulatory Metabolite Fructose 2,6-Bisphosphate

United States Department of Agriculture, Agricultural Research Service, North Carolina State University, Raleigh, North Carolina 27695-7631, Department of Crop Science, North Carolina State University, Raleigh, North Carolina 27695-7631, Department of Botany, North Carolina State University, Raleigh, North Carolina 27695-7631

Diurnal changes in the regulatory metabolite, fructose-2,6-bisphosphate (F26BP), and key metabolic intermediates of sucrose biosynthesis were studied in maize (Zea mays L. cv Pioneer 3184) during a day-night cycle. Whole leaf concentrations of dihydroxyacetonephosphate (DHAP) and fructose 1,6-bisphosphate changed markedly during the photoperiod. DHAP concentration was correlated positively with the rate of sucrose formation in vivo (assimilate export plus sucrose accumulation) and extractable activity of sucrose phosphate synthase (SPS). The changes closely followed net photosynthetic rate, which tracked irradiance. The other metabolic intermediates measured (glucose 6-phosphate, fructose 6-phosphate, and UDP-glucose) were either relatively constant over the 24 hour period or changed in a different pattern. Diurnal changes in leaf F26BP concentrations were pronounced, and fundamentally different than the pattern reported with other species. F26BP concentration decreased at the beginning of the day and remained low and constant; a 3- to 4-fold increase occurred with darkness, and slowly declined thereafter. In general, leaf F26BP concentration was negatively correlated with net photosynthetic rate, and also leaf DHAP concentration. Consequently, co-ordination of the regulation of cytosolic fructose 1,6-bisphosphatase and SPS was apparent. The results support the postulate that in maize leaves the activation state of SPS may be dependent on availability of DHAP and possibly other metabolites.

³ Present address: E. I. duPont de Nemours, Agricultural Products Department, Crop Research Laboratory; P.O. Box 30, Newark, DE 19714.

¹ Cooperative investigation with the United States Department of Agriculture, Agricultural Research Service, and the North Carolina Agricultural Research Service, Raleigh, NC 27695-7601. Paper No. 10508 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7601. Supported in part by Japan-United States Cooperative Research Program (National Science Foundation grant 84-14711) on Biochemical Factors Related to Photosynthetic Productivity of C₃ and C₄ Plants. A part of the preliminary work was supported by a grant to Hideaki Usuda from the Japanese Ministry of Education, Science, and Culture.