Guar is an economic crop due to guar gum which is extracted from seeds and is used in several industries such as food, ink, plastics, pharmaceutical industry, and cosmetics. It can also be used as a cover crop, animal feed, and green manure. L-Tryptophan (L-β-3-indolylalanine) is a precursor of auxin which regulates plant growth and development. Nicotinamide is known as the amide form of vitamin B3. It is a constituent of the pyridine nucleotide coenzymes involved in many enzymatic

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... uction reactions in cells. L-Tryptophan and nicotinamide are used in this study in order to improve guar growth, yield, and chemical constituents of seeds. Results: The highest records of plant height and fresh and dry weights of leaves were recorded for plants treated with 300 mg/l nicotinamide followed by foliar treatment with 300 mg/l tryptophan. Fresh and dry weights of stems, number of pods/plant, fresh and dry weights of pods, pods yield, seeds yield, and straw yield followed the same trend. Total protein in guar seeds was significantly increased due to foliar treatment with tryptophan, especially in plants treated with 300 mg/l tryptophan, followed by plants treated with 300 mg/l nicotinamide. Total carbohydrates (mg/g dry wt.), total soluble sugars (mg/g dry wt.), total insoluble sugars (mg/g dry wt.), proline (μmol/g dry wt.), and total phenolic compounds (mg/g dry wt.) in the leaves followed the same trend. Conclusion: It could be concluded that guar growth and yield are maximized with foliar treatment with nicotinamide (300 mg/l). Also, chemical constituents of seeds improved with nicotinamide and tryptophan treatments (each at 300 mg/l).