Environmentally-induced changes in protein composition in developing grains of wheat are related to changes in total protein content

Nitrogen (N) nutrition, post-anthesis temperature and drought-induced changes in the kinetics of accumulation of dry mass, total grain N and protein fractions (albumins-globulins, amphiphils, gliadins, and glutenins) contents were examined for winter wheat (Triticum aestivum L.). Crops were grown in controlled environment tunnels in 1994 and 1998. In 1994, five post-anthesis temperatures averaging from 15-25 degrees C were applied during grain-filling. In 1998 two post-anthesis temperatures averaging 13 degrees C and 20 degrees C were applied and factorized with two post-anthesis water regimes. In 1994 crops also were grown in the field, where different application rates and timing of N nutrition were tested. When expressed in thermal time, the kinetics of accumulation of the protein fractions were not significantly affected by post-anthesis temperature or drought; whereas N nutrition significantly increased the rate and duration of accumulation of storage proteins. Albumin-globulin proteins accumulated during the early stage of grain development. The rate of accumulation of that fraction decreased significantly at c. 250 degrees Cd after anthesis, when the storage proteins (gliadins and glutenins) started to accumulate significantly. Single allometric relationships for the different environmental conditions exist between the quantity of each protein fraction and the total quantity of N per grain. From these results it was concluded that (1) the process of N partitioning is neither significantly affected by post-anthesis temperature or drought nor by the rate and timing of N nutrition and (2) at maturity, variations in protein fraction composition are mainly because of differences in the total quantity of N accumulated during grain-filling.