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In order to compare photosynthetic features of triticale, bread wheat, and barley under water deficit conditions, this experiment was carried out in Kurdistan province in western Iran. Four genotypes of triticale, three cultivars of bread wheat, and a new variety of barley were compared under well watered (Ψ_soil= -3 bars) and soil water deficit (Ψ_soil= -12 bars) conditions in a randomized complete block design (RCBD) with a split-plot arrangement. Biomass production at anthesis accompanied with gas exchanges and chlorophyll fluorescence of flag leaves, as indicators of photosynthetic function of plant, were determined in each treatment. The results showed that by imposing water deficit, photosynthetic rate (P_n) was reduced in all studied genotypes irrespective of plant species. Under water deficit conditions, the highest P_n (6.86 and 5.90 µmol m^-2 s^-1) was found in bread wheat variety Pishgam and, triticale genotype No. 1, while the lowest value (3.63 µmol m^-2 s^-1) was found in barley variety Bahman. Similar trend was observed for the maximum quantum yield of primary photochemistry (F_v/F_m) and performance index (PI). Significant positive correlations were found between biomass production at anthesis and both P_n (r= 0.83^**) and F_v/F_m (r= 0.77^*). Our data revealed the better performance of Pishgam than Alvand and Zarrin in the reduction rate of biomass at anthesis and photosynthetic features against soil water deficit conditions. Overall, triticale was less affected by water deficit in comparison with wheat and barley in terms of photosynthetic function as indicated by less reduction in P_n, PI, and F_v/F_m.

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Canopy temperature (CT) is used as a selection tool to improve crop adaptation to drought. The aim of this work was to investigate association of some photosynthetic characters with CT during grain filling in three cereal species. For this objective, a two-year study (2009-2011) was carried out in Kurdistan Province in western Iran. Four genotypes of triticale, three cultivars of bread wheat, and a new variety of barley were compared under well watered (WW, Ψ_{soil water}= -3 bar) and deficit water (DW, Ψ_{soil water}= -12 bar) conditions in a randomized complete block design (RCBD) with a split-plot arrangement. Compared with well-watered plants, water stressed plants displayed 1.44°C higher canopy temperature irrespective of plant species. Under water stress condition, the high yielding genotypes had lower canopy temperature than low yielding ones by 1.23°C. Results showed that under water deficit condition triticale relative to commercial cultivar of wheat and barley had a higher adaptability to drought as indicated by its higher yield (59.5 g m^-2 more than average) and lower CT (0.28°C lower than average). The main physiological traits correlated with canopy temperature under DW treatment were stomatal conductance (g_s) (r= -0.73*), photosynthetic rate (P_n) (r= -0.76*), the maximal quantum yield of primary photochemistry (F_v/F_m) (r= - 0.71*), chlorophyll content at grain filling (r= -0.72*) and leaf temperature (LT) (r= 0.82**). Thus, canopy temperature seems to play an important role in the physiological basis of grain yield in different cereal species, and can be used as a selection tool in breeding programs under water deficit condition in Iran. 

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The objective of this study was to assess changes in proline, Glycine Betaine (GB), photosynthetic pigment concentration, Membrane Stability Index (MSI), and grain yield of wheat cultivars induced by Supplemental Irrigation (SI) in the terminal growth stages. Two field experiments with four irrigation levels (rainfed, SI at booting stage, SI at booting and anthesis stages, SI at booting, anthesis, and grain filling stages) and five cultivars (Rejaw, Sardari, Homa, Azar2, and Sirwan) were conducted during the 2015-2017 growing seasons. Results indicated that, overall, SI increased cultivars' chlorophyll concentration, MSI, and grain yield. Proline and GB highly accumulated under drought stress, but rapidly decreased after SI; the severity of the decrease in proline concentration was more remarkable. Sardari and Azar2 cultivars exhibited greater MSI, proline, and GB accumulation during drought stress and more rapid recovery from drought. Our results suggest that the ability of the wheat cultivars to maintain functions during drought and recover after SI during the terminal growth stage is essential for determining final grain yield.