Photosynthetic traits of triticale in grain filling period as affected by nitrogen fertilizer, silicon foliar application and water stress

In order to investigate the interaction effect of nitrogen (N) and silicon foliar application on photosynthetic traits of triticale under water stress conditions, a split factorial experiment in a randomized complete block design with three replicates was conducted at the Experimental Farm of College of Agriculture and Natural Resources of Darab – Shiraz University in 2017-2018 growing season. Treatments included: two levels of irrigation as the main plots [normal irrigation; irrigation based on the plant's water requirement up to the physiological maturity (IRN) and water deficit (water stress); irrigation based on the plant's water requirement up to the anthesis stage (withholding of irrigation after anthesis) (IRDI)]. Also, sub plots were two levels of silicon foliar application [0, and 3 mM] and three N fertilizer levels [N0, no nitrogen fertilizer (control); N100, 100 kg N ha-1; N150, 150 kg N ha-1]. The results showed that the IRDI reduced the photosynthesis at the milking and soft dough stages, however, this reduction was not constant in the different N levels and the highest reduction was occurred in 150 kg N ha-1 (44% and 55% reduction in the milking and soft dough stages, respectively). A similar trend was observed in the grain yield. Silicon foliar application could cause the reduction of distractive effects of water stress on photosynthesis and related traits (stomatal conductance and instantaneous water use efficiency), independently of N fertilizer supply. Totally, application of 150 and 100 kg N ha-1 is recommended for high photosynthesis rate of triticale in normal and water deficit, respectively. Furthermore, silicon foliar application (3 mM) was suggested for deminishing the hurmful effects of the severe water stress after anthesis on photosynthesis and its related traits in South of Iran.