NPK-Co-Doped Quantum Dots Enhance Vegetative Growth and Yield Capacity of Two Wheat Cultivars Grown Under Normal and Drought Conditions

Abstract Nitrogen, phosphorus, and potassium co-doped quantum dots (NPK-QDs) were synthesized by microwave-assisted hydrothermal method. The obtained NPK-QDs possessed unique optical properties with blue luminescence under ultraviolet irradiation. Fourier-transform infrared analysis revealed various peaks proving the successful tertiary doping of NPK into the QDs carbon skeleton. Also, the plenty of oxygen-containing functional groups, confirmed by high carboxyl and hydroxyl content, largely contributed to the hydrophilic nature of these QDs. Transmission electron and atomic force microscopies indicated zero-dimensional nanometric features of NPK-QDs. Cytotoxicity assessment against two human cell lines showed that NPK-QDs were safe-by-design. Seed priming of two wheat cultivars (Sakha 95 and Masr 3) in 50 and 100 mg l − 1 NPK-QDs enhanced their growth at heading stage under control and drought conditions. This was indicated from the better shoot agronomy, enhanced leaf anatomy, more pigment and carbohydrate content, and higher leaf capacity for gas exchange. Moreover, NPK-QDs improved water status, activated enzymatic antioxidant defense system, and promoted osmoprotection of the wheat plants. Consequently, their yield attributes (biological, crop, economic, and straw yield as well as 100-kernel mass) and nutritional value of the yielded grains (carbohydrate and protein content) were enhanced. Multivariate analysis based on the concerned vegetative and yield traits indicated that NPK-QDs had more obvious effect on the drought-sensitive cultivar Masr 3 than its tolerant relative Sakha 95. Interestingly, NPK-QDs improved the performance of the droughted Masr 3 plants to be even better than their unstressed control synonyms. Thus, NPK-QDs can be recommended as novel plant growth promoters to improve wheat growth and productivity under control and drought conditions.