Abstract
Herbaceous peony (Paeonia lactiflora Pall.) is a traditional famous flower, but its poor inflorescence stem quality seriously constrains the development of the cut flower. Mechanical strength is an important characteristic of stems, which not only affects plant lodging, but also plays an important role in stem bend or break. In this paper, the mechanical strength, morphological indices and microstructure of P. lactiflora development inflorescence stems were measured and observed. The results showed that the mechanical strength of inflorescence stems gradually increased, and that the diameter of inflorescence stem was a direct indicator in estimating mechanical strength. Simultaneously, with the development of inflorescence stem, the number of vascular bundles increased, the vascular bundle was arranged more densely, the sclerenchyma cell wall thickened, and the proportion of vascular bundle and pith also increased. On this basis, cellulose and lignin contents were determined, PlCesA3, PlCesA6 and PlCCoAOMT were isolated and their expression patterns were examined including PlPAL. The results showed that cellulose was not strictly correlated with the mechanical strength of inflorescence stem, and lignin had a significant impact on it. In addition, PlCesA3 and PlCesA6 were not key members in cellulose synthesis of P. lactiflora and their functions were also different, but PlPAL and PlCCoAOMT regulated the lignin synthesis of P. lactiflora. These data indicated that PlPAL and PlCCoAOMT could be applied to improve the mechanical strength of P. lactiflora inflorescence stem in genetic engineering.
Highlights
Herbaceous peony (Paeonia lactiflora Pall.) is a traditional famous flower with a cultivation history of more than 4000 years in China, which has shared the name ‘‘the king and minister of flowers’’ with tree peony [1]
Stem mechanical strength is related to the morphological indices of a plant, i.e., plant height, diameter and dry weight of stem etc
We found that the correlation between mechanical strength and fresh weight of inflorescence stem did not reach a significant level, which indicated that the fresh weight of an inflorescence stem could not accurately reflect the texture density of an inflorescence stem, and could not be used as an indicator to estimate mechanical strength
Summary
Herbaceous peony (Paeonia lactiflora Pall.) is a traditional famous flower with a cultivation history of more than 4000 years in China, which has shared the name ‘‘the king and minister of flowers’’ with tree peony [1]. In Europe and the United States, herbaceous peony, known as the “wedding flower”, is a high-grade cut flower for weddings and other festive occasions, so its market prospect is very broad [2,3]. We find that the P. lactiflora inflorescence stem is easy to bend or break and can not support flower weight, which seriously affects the quality of the cut flower. Previous research reveal that mechanical strength is an important characteristic of stem, which affects plant lodging, and plays an important role in the inflorescence stem bend or break [4,5].
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