Abstract: 【Objective】The hexi corridor region in gansu province experiences high temperatures in summer, cold and cool conditions in autumn and winter, scarce rainfall, barren soil, and varying degrees of salinization, which can lead to premature yellowing and senescence of grape leaves. This results in weakened photosynthesis, reduced assimilates, insufficient nutrient storage in the plant, and often leads to insufficient fruit ripening and a decrease in yield, severely restricting the sustainable development of delayed cultivation of grapes in facilities. Dopamine has physiological functions such as enhancing the photosynthetic capacity of crops, promoting plant growth and development, and improving fruit quality. To study the mechanism of dopamine's impact on the photosynthetic performance and quality of grapes, and to screen for suitable control concentrations and methods for production. 【Methods】The experiment used Shine Muscat grapes grown in a delayed facility cultivation as the material, setting four exogenous dopamine concentrations: 50 μM (T1), 100 μM (T2), 150 μM (T3), and 200 μM (T4), with water as the control (CK). The whole plant was sprayed at different stages: the initial flowering stage, young fruit stage (30 days after flowering), fruit expansion stage (60 days after flowering), and color change stage (90 days after flowering). Photosynthetic performance of the leaves at different stages and fruit quality indicators at maturity were measured. 【Results】The results showed: (1) Dopamine treatment could enhance the leaf quality of Shine Muscat grapes cultivated in delayed facilities, with the treatment at T2 being the most pronounced. Under the T2 treatment, the leaf thickness, palisade tissue, spongy tissue, upper epidermis, lower epidermis thickness, and palisade to spongy tissue ratio at different stages increased by 8.72%, 13.68%, 8.62%, 23.18%, 12.44%, and 3.92% respectively, compared to the control (CK). (2) Dopamine treatment could improve the photosynthetic performance of grape leaves. Specifically, the average content of Chl a at different stages increased by 24.42%, 48.37%, 42.56%, and 19.08% with treatments T1 to T4 respectively, compared to CK; the average content of Chl b increased by 30.67%, 61.26%, 48.17%, and 16.34% respectively; the average content of Car increased by 60.76%, 111.72%, 99.30%, and 31.37% respectively; the average content of Chl t increased by 26.88%, 53.44%, 44.77%, and 18.00% respectively; the average net photosynthetic rate (Pn) increased by 7.09%, 16.97%, 12.69%, and 7.86% respectively; the average stomatal conductance (Gs) increased by 5.17%, 18.28%, 14.14%, and 5.17% respectively; the average intercellular CO2 concentration (Ci) decreased by 4.55%, 6.27%, 5.86%, and 2.48% respectively; the average transpiration rate (Tr) increased by 3.98%, 8.17%, 7.45%, and 4.95% respectively; and the average water use efficiency (WUE) increased by 3.01%, 7.83%, 4.87%, and 2.92% respectively. All the above indicators were optimal with the T2 treatment, significantly higher than the control (P＜0.05). (3) Dopamine treatment improved the appearance quality of grape fruits, soluble solids, sugar-acid ratio, soluble sugars, Vc, total phenols, anthocyanins, total flavonoids, and sugar components (fructose, glucose, and sucrose) content, while reducing the content of titratable acidity and tannins in the fruits, with the T2 treatment showing the most significant effect and the T3 treatment being the next best. Specifically, the single fruit weight increased by 26.32%, 16.56%, 7.54%, and 3.53% with treatments T1 to T4 respectively, compared to the control (CK); fruit firmness increased by 9.27%, 33.66%, 19.51%, and 1.46% respectively; the content of soluble solids increased by 10.64%, 13.83%, 11.57%, and 8.38% respectively; the content of titratable acidity decreased by 6.55%, 10.48%, 11.79%, and 21.83% respectively; the content of soluble sugars increased by 3.32%, 4.92%, 3.36%, and 3.12% respectively; the content of total phenols increased by 40.82%, 20.86%, 12.32%, and 6.56% respectively; the content of tannins decreased by 19.78%, 26.35%, 20.13%, and 18.45% respectively; the content of fructose increased by 1.78%, 7.92%, 6.65%, and 0.06% respectively; the content of glucose increased by 27.17%, 23.64%, 21.00%, and 20.18% respectively.【Conclusion】Compared to the control (CK), dopamine treatment can improve the leaf quality of Shine Muscat grapes cultivated in delayed facilities and enhance their photosynthetic performance, thereby improving the fruit quality. Treatment with 100 μM dopamine can significantly increase leaf thickness, palisade and spongy tissue thickness, upper and lower epidermis thickness, and the palisade to spongy tissue ratio, and improve the content of photosynthetic pigments in the leaves, thereby enhancing the utilization rate of chlorophyll light energy and the net photosynthetic rate. After dopamine treatment, the appearance quality of grape fruits, soluble solids, sugar-acid ratio, soluble sugars, vitamin C (Vc), total phenols, anthocyanins, total flavonoids, fructose, glucose, and sucrose content were increased, while the content of titratable acidity and tannins in the fruits were reduced. Through principal component analysis to comprehensively evaluate the impact of various indicators on the fruit quality of Shine Muscat grapes, it was concluded that the treatment with 100 μM dopamine was the most effective.
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