The relation between tillering and accumulated temperature by influence by spraying some amino acid for three bread wheat cultivars
Two field experiments were conducted at station affiliated to College of Agricultural Engineering Sciences University of Baghdad during the two winter seasons 2016- 2017 and 2017 and 2018 according to the Randomized Complete Block Design (RCBD) of three replicates within the split-plot arrangement. The objective of the study was to check the physiological act of three bread wheat varieties affected by amino acids reflecting on the characteristic of tillering relating to the heat accumulation and how that reflects on the grain yield. The experiment included two factors: first, the main plots, included three wheat varieties (Iba 99, Buhooth 22, and Abu-Graib 3) and the second, the sub-plots, was the Amino acids, L-Tryptophan, L-Glycine, and L-Lysine at two concentrations (50 and 100 mg.L-1) of each and L-Cystin at two concentrations (50 and 150 mg.L-1). The treatments of spraying amino acids were applied twice: the first was at the stage of three leaves on the main stem (ZGS:13) and the second was at the stage of entering plants the flowering stage (ZGS:60). Results show the significant superiority of Buhooth 22 in the number of tillers. plant-1. It produced the highest number of tillers per plant and the highest number of tillers per square meter in the two seasons, respectively. The highest number of tillers. plant-1 in the two seasons was produced when plants entered the elongation stage ZGS: 31. Buhooth 22 produced the highest grain yield. The treatment of spraying 50mg.L-1 Tryptophan was significantly superior in the characteristics of tillering and grain yield in the two seasons. It produced the highest number of tillers. plant-1 during the whole growth season. The plants of all varieties required an accumulated temperature of 325 GDD (Growing Day Degrees) to commence tillering and 660- 900 GDD to maximize the number of tillers. plan-1. These temperatures almost represent one-third of the total accumulated temperature (2250-2650 GDD) during the complete growth seasons in both seasons. The effect of the interaction between the two studied factors was significant in the characteristics of tillering and grain yield. We conclude from the study the necessity of adopting the accumulated parameter to determine when the plant enters the specified growth stage, in addition to the response of the varieties to the treatment of spraying the amino acids reflecting on the grain yield.