Effects of Inflorescence Stem Structure and Cell Wall Components on the Mechanical Strength of Inflorescence Stem in Herbaceous Peony

Abstract

Herbaceous peony (<em>Paeonia lactiflora</em> 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 <em>P. lactiflora</em> 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, <em>PlCesA3</em>, <em>PlCesA6</em> and <em>PlCCoAOMT</em> were isolated and their expression patterns were examined including <em>PlPAL</em>. 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, <em>PlCesA3</em> and <em>PlCesA6 </em>were not key members in cellulose synthesis<em> </em>of<em> P. lactiflora</em> and their functions were also different, but <em>PlPAL</em> and <em>PlCCoAOMT</em> regulated the lignin synthesis of<em> </em><em>P. lactiflora</em>. These data indicated that <em>PlPAL</em> and <em>PlCCoAOMT</em> could be applied to improve the mechanical strength of <em>P. lactiflora</em> inflorescence stem in genetic engineering.

Keywords

• &lt;em&gt;Paeonia lactiflora&lt;/em&gt;
• mechanical strength
• cloning
• gene expression