Temporal dynamics in wheat grain zinc distribution: is sink limitation the key?
Enhancing the zinc (Zn) in wheat (Triticum aestivum L.) grain is a breeding aim in order to improve human Zn nutrition. This study analyses the temporal dynamics of Zn concentrations in grain tissues during grain filling. On examination of Zn distribution in grains of plants grown at either 1 or 5 mg Zn/kg soil, the Zn concentration of the crease was found to increase by 5 to 9 fold between 7 and 34 DAA, while that of the endosperm decreased by 7 to 45%. Because the Zn turnover rate (per d) in the crease tissues was either independent of the Zn application level or higher at the lower Zn application level, and the Zn concentration increased with time during grain filling while the turnover rate gradually decreased, it seems that the process of transfer within the grain beyond the grain crease limits the endosperm allocation rather than the input of Zn into the grain. Our data do not allow us to establish whether sink strength for Zn in the endosperm or the Zn transport capacity of the involved membranes is limiting.
The Proceedings of the International Plant Nutrition Colloquium XVI. (University of California, Davis). Paper 1331.