Translocation from the flag leaf of winter wheat triticum aestivum cultivar maris huntsman in the field
Bell, C.J.; Incoll, L.D.
Journal of Experimental Botany 33(136): 896-909
ISSN/ISBN: 0022-0957 Accession: 006829093
Translocation of assimilate from the flag leaf of winter wheat (T. aestivum cv. Maris Huntsman) was studied in the field by monitoring the export of photo-assimilated [14C]CO2 with a Geiger-Muller counter-placed under the fed area of leaf. The resulting export curve was analyzed as a sum of 2 exponential terms and interpreted as a 2-pool compartmental system. The rate constant for export from the leaf increased slightly from maximum elongation to anthesis, then declined to almost half its peak value just before the leaf lost all visible chlorophyll. The inter-pool transfer rate constants did not change significantly over the same period, but all rate constants varied with time of day. Short-term changes in the environment of the flag leaf had no discernible influence on translocation in the field. The time constants of the 2 pools of assimilate agreed with those for other species reported in the literature. Evidently, sucrose is stored in the vacuole of mesophyll cells. The variations in rate constants with time of day and deviations of the export data from the 2-pool model suggest that export and inter-pool transport have saturation kinetics. A model with Michaelis-Menten kinetics was formulated and simulations of this model showed similar deviations from a simple 2-pool system as the experimental ones.