Objective To explore the effects of different gradients of substrate pH (4.5, 5.5, 6.5, 7.5) on the flowering quality of Primula vulgaris, and to provide a certain theoretical basis for the refined cultivation of Primula vulgaris.

MethodsBased on four different-colored P. vulgaris varieties ('Beautiful Scenery,' 'Hot Lover,' 'Blue Onstar,' 'Huangli'), sulfuric acid ferrous and sodium hydroxide solutions were used to adjust the pH of potted substrate to different gradients. Morphological indicators such as plant height and flower leaf growth were observed, and data such as cell protective enzyme activity, pigment content, and membrane permeability were measured to study the effects of substrate pH on the flowering quality of P. vulgaris.

ResultsP. vulgaris had better flower morphology at substrate pH5.5 and pH6.5, and growth was inhibited at all other pH conditions. The L* value of the petals decreased under acid-alkaline stress, while the content of anthocyanins and flavonoids exhibited a decreasing trend with an increase in substrate pH. The petal cell sap pH of 'Hot Lover' showed a slight increase compared with control treatment (CK). Compare with CK, the CAT activities of the four varieties increased significantly under pH 4.5 treatment. Correlation analysis between morphological and physiological indicators indicated that POD had the highest correlation with carotenoid content and the lowest correlation with anthocyanin content. The results of principal component analysis and a comprehensive evaluation based on membership functions suggested that petal cell sap pH, blade relative water content, flowering count, CAT activity, soluble sugar content, and plant height could be used as the primary indicators for evaluating the flowering quality of P. vulgaris under different substrate pH conditions. Regardless of the substrate pH conditions, 'Blue Onstar' consistently exhibited the highest flowering quality.

Conclusion The optimal substrate pH for the best flowering quality of P. vulgaris falls within the range of 5.5 to 6.5. Under different substrate pH stresses, the flowering quality of 'Blue Onstar' was the highest, followed by 'Beautiful Scenery,' 'Hot Lover,' and 'Huangli.'