Effect of Foliar Application of Glutamine on Growth, Physiological Characteristics and Protein Content of Different Sorghum [Sorghum bicolor (L.) Moench] Varieties
Background: Glutamic acid plays an important role by increasing the plant’s resistance to climate change and tolerance to unfavourable conditions such as high temperature, water stress, salinity and snow. It also acts as a strong chelating agent for trace elements and environmentally friendly fertilisers. Methods: An experiment was conducted in plastic pots during the spring 2023 season in Kirkuk governorate, Iraq, to evaluate the effects of sorghum plant varieties (Rabih, Khair and Inkhath) under different doses of foliar application of glutamine (0, 40, 80 and 100 mg L-1) on growth, physiological characteristics and protein percent in grains. This experiment was designed using a completely randomized design (CRD) with three replications. Result: The Inkhath variety significantly required fewer days to reach 50% flowering: 62.10 days. Also, it was significantly superior in plant height, leaf chlorophyll content, plant leaf number and flag leaf area, reaching 115.23 cm, 55.50 SPAD, 10.59 leaves plant-1 and 368.82 cm2, respectively. The concentration of 100 mg L-1 glutamic acid was significantly the earliest at 50% flowering with the highest plant height, leaf chlorophyll content, leaf number, flag leaf area and grain protein percentage, reaching 58.31 days, 116.22 cm, 56.53 SPAD, 10.44 leaves plant-1, 391.68 cm2 and 14.36%, respectively. The interaction between Inkhath variety and spraying with 100 mg glutamic acid was significantly the earliest in 50% flowering with the highest means in plant height, leaf chlorophyll content, plant leaf number and flag leaf area, reaching 55.60 days, 121.67 cm, 58.00 SPAD, 11.06 leaves plant-1 and 450.06 cm2, respectively, as well as the interaction between Rabih variety with 100 mg glutamic acid was significantly recorded highest grain protein percentage 14.88 %. The Inkhath sorghum variety showed a high response to a high spraying rate of 100 mg L-1 glutamic acid, which improved growth, physiological traits and grain protein percentage.