Post-Anthesis Dry Matter and Nitrogen Dynamics in Durum Wheat as Affected by Nitrogen and Temperature during Grain Filling

Durum wheat (Triticum turgidum L. var. durum Desf.) is commonly grown in Mediterranean conditions, where temperature stress during grain filling can limit productivity. This research was performed to evaluate the effect of temperature during grain filling on dry matter and nitrogen dynamics in two Italian durum wheat varieties, Appio and Creso, grown with different nitrogen availabilities. The experiment compared two different temperature regimens, one within the normal range occurring during grain filling in Central Italy, the other within the normal range occurring in the southern regions of Italy (20/15 degrees C and 28/23 degrees C day/night, respectively). Plants were grown in pots outdoor until anthesis and afterward were placed in growth chambers. Results showed that nitrogen fertilization and post-anthesis temperature affected growth, accumulation and partitioning of dry matter and N in durum wheat which, in turn, modified grain yield and N content. Grain yield was better expressed at 20/15 degrees C, while grain protein concentration was favoured under the 28/23 degrees C temperature regime. Higher temperature promoted remobilization of dry matter and restrained current photosynthesis, but reduced grain yield, indicating that the loss of photosynthesis could not compensate for the gain from increased remobilization. Grain N content, on the contrary, was promoted under the higher temperature regime, as high temperature reduced N remobilization but did not inhibit root water and nitrogen uptake, given that no water shortage occur.