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 PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Moutot, F. Articles by Pernollet, J.-C. Search for Related Content PubMed PubMed Citation Articles by Moutot, F. Articles by Pernollet, J.-C. Agricola Articles by Moutot, F. Articles by Pernollet, J.-C.

Articles

Relationship between Photosynthesis and Protein Synthesis in Maize

I. Kinetics of Translocation of the Photoassimilated Carbon from the Ear Leaf to the Seed

Laboratoire du Métabolisme et de la Nutrition des Plantes, Département de Physiologie et Biochimie Végétales, Centre I.N.R.A, route de St-Cyr, 78000 Versailles, France, Laboratoire d'Etude des Protéines, Département de Physiologie et Biochimie Végétales, Centre I.N.R.A, route de St-Cyr, 78000 Versailles, France

To gain a better understanding of the biochemical basis for partitioning of photosynthetically fixed carbon between leaf and grain, a ¹⁴CO₂ labeling study was conducted with field-grown maize plants 4 weeks after flowering. The carbon flow was monitored by separation and identification of ¹⁴C assimilates and ¹⁴C storage components within each tissue during the chase period (from 4 to 96 hours) following a 5 minute ¹⁴CO₂ pulse. In the labeled ear leaf, the radioactivity strongly decreased to reach, at the end of the experiment, about 12% of the total incorporated radioactivity, mostly associated with sucrose and proteins. Nevertheless, an unexpected reincorporation of radioactivity was observed either in leaf starch or proteins, the day following the pulse. Conversely, the radioactivity in the grain increased to attain 66% of the total incorporated ¹⁴C after a 96 hour chase. The photosynthates, mostly sucrose, organic and free amino acids, rapidly translocated towards the developing seeds, served as precursors for the synthesis of seed storage compounds, starch, and proteins. They accumulate in free form for 24 hours before being incorporated within polymerized storage components. This delay is interpreted as a necessary prerequisite for interconversions prior to the polycondensations. In the grain, the labeling of the storage molecules, either in starch or in storage protein groups (salt-soluble proteins, zein, and glutelin subgroups), was independent of their chemical nature but dependent on their pool size.