Objective This study aimed to elucidate the coloration mechanism of Acer griseum (Franch.) Pax leaves during autumn senescence by quantifying changes in physiological and biochemical indicators. We analyzed the correlations among leaf color parameters, physiological growth indicators, and environmental factors to identify the key drivers behind the color transition.

Method Based on the Acer griseum during the autumn color change period, the changes in leaf color parameters (Lab values), pigment contents (chlorophyll, carotenoid, anthocyanin and flavonoid), leaf morphology(thickness, length, width and area), leaf penetrating (soluble sugar and soluble protein), and mineral elements (total nitrogen, phosphorus and organic carbon) were quantitatively determined and analyzed. Correlation analyses were conducted to assess the relationships among these physiological and biochemical indicators and environmental factors.

Result 1) As leaves gradually changed from green to deep red in autumn, lightness parameter L* value and the hue parameter a* value increased from 29.11 to 42.22, and −10.34 to 32.00, respectively. Conversely, chlorophyll and carotenoids gradually decreased to 2.40% and 30.52%, respectively. The contents of anthocyanins and flavonoids continued to increase throughout the color-change process, reaching 34.66 and 2.97 times those of the early stage, respectively. The mass ratios of carotenoids / total chlorophyll, anthocyanins / total chlorophyll and flavonoids / total chlorophyll gradually increased as the leaves turned red. Total nitrogen content gradually decreased, whereas soluble sugar, soluble protein and total organic carbon increased first and then declined. In contrast, total phosphorus showed an opposite trend_\-first declining and then growing. Overall changes in leaf phenotypic parameters were minor, though all decreased slightly by the end of coloration. 2) Chlorophyll was significantly negatively correlated with soluble protein, soluble sugar, a* value, anthocyanin and flavonoids (p<0.05), and significantly positively correlated with carotenoids and total nitrogen (p<0.05); Anthocyanin was significantly negatively correlated with chlorophyll, carotenoids and total nitrogen (p<0.05), and significantly positively correlated with a* value, flavonoids and ratio of leaf pigment contents (p<0.05). 3) Environmental factors such as temperature and duration of sunlight were significantly positively correlated with chlorophyll and carotenoids (p<0.05), and significantly negatively correlated with anthocyanins, flavonoids and the ratio of leaf pigment contents (p<0.05). Air humidity was significantly negatively correlated with the ratio of leaf pigment contents (p<0.05).

Conclusion The fundamental cause of autumn color change in leaves of Acer griseum from green to red is the degradation of chlorophyll and carotenoids, accompanied by large-scale synthesis of anthocyanins, the increase of flavonoids and the rise in the proportion of various pigments. Soluble sugar, soluble protein, and total nitrogen of the leaves are also key factors that directly influence leaf coloration. Low temperature and shorter duration of sunlight accelerate the degradation of chlorophyll and carotenoids, which are the main limiting environmental factors affecting the color of the leaves of Acer griseum.