Abstract:

Objective: This study aims to explore the dynamic changes in morphology and physicochemical indexes during the flowering process of tree peony with different flower types, so as to provide a theoretical basis for the regulation of flower types and cultivation management of tree peony in the future. Method: The flower buds (flowers) of 13 different developmental stages in the flowering process of the single-petal cultivar Paeonia ostii ‘Fengdan’ and the chrysanthemum cultivar P. suffruticosa ‘Lianhe’ were used as experimental materials. The dynamic changes in the external morphology and the relevant important physiological and biochemical indexes [indole acetic acid (IAA), gibberellin acid (GA₃), abscisic acid (ABA), zeatin riboside (ZR), soluble sugar, soluble protein, superoxide dismutase (SOD), peroxidase (POD)] were determined through observation and measurements. Result: The flower buds (flowers) of P. ostii ‘Fengdan’ and P. suffruticosa ‘Lianhe’ showed different degrees of growth in width and height from the overwintering bulb stage to the full blooming stage. Both of them began to grow rapidly at the big-bell stage and the small-bell stage, respectively, and reached their peak at the full blooming stage. From the initial flowering stage to the full blooming stage, the ZR content of P. ostii ‘Fengdan’ increased, while ZR content of P. suffruticosa ‘Lianhe’ continued to decrease. The change trends of soluble sugar and soluble protein contents of P. ostii ‘Fengdan’ and P. suffruticosa ‘Lianhe’ were consistent, but the content of soluble sugar and soluble protein of P. ostii ‘Fengdan’ was always higher than that of P. suffruticosa ‘Lianhe’ from the color-exposure stage. Both P. ostii ‘Fengdan’ and P. suffruticosa ‘Lianhe’ showed an increasing trend in SOD content during the blooming stage compared to the previous stage. As the developmental stage continued, the SOD content of P. ostii ‘Fengdan’ showed a tendency to first increase and then decrease, while P. suffruticosa ‘Lianhe’ showed a tendency to first decrease and then increase. The change trend of POD content in flower buds (flowers) of P. ostii ‘Fengdan’ and P. suffruticosa ‘Lianhe’ at different development stages was basically the same, but there were slight differences in the magnitude of variation. Conclusion: The rapid growth stage of P. ostii ‘Fengdan’ is from the big-bell stage to the full blooming stage, and the fastest growth stage of P. suffruticosa ‘Lianhe’ is from the small-bell stage to the full blooming stage. High levels of IAA and low levels of ABA and GA₃ can promote the flowering of P. ostii ‘Fengdan’ and P. suffruticosa ‘Lianhe’ flowers. High levels of ABA/IAA, ABA/GA₃ and low levels of ZR/IAA, ZR/GA₃ may be more conducive to breaking dormancy of tree peony buds. There may be greater fluctuations in various hormones during budding stage and the circular peach stage. The stage of highest content of nutrients and antioxidant enzymes in buds of P. ostii ‘Fengdan’ and P. suffruticosa ‘Lianhe’ is the stage of budding stage. The small-bell stage is the key stage for differentiation of different varieties of peonies towards different flower types.

Key words: tree peony, flower type, endogenous hormones, nutrients, antioxidant enzymes