School of Landscape Architecture, Beijing Forestry University, Beijing, 100083, China; National Engineering Research Center for Floriculture, Beijing, 100083, China; Beijing Laboratory of Urban and Rural Ecological Environment, Beijing, 100083, China; Beijing Key Laboratory of Ornamental Plants Germplasm Innovation & Molecular Breeding, Beijing, 100083, China.
School of Landscape Architecture, Beijing Forestry University, Beijing, 100083, China; National Engineering Research Center for Floriculture, Beijing, 100083, China; Beijing Laboratory of Urban and Rural Ecological Environment, Beijing, 100083, China; Beijing Key Laboratory of Ornamental Plants Germplasm Innovation & Molecular Breeding, Beijing, 100083, China.
J Plant Physiol. 2023 Apr;283:153963. doi: 10.1016/j.jplph.2023.153963. Epub 2023 Mar 4.
The quality of cut Paeonia lactiflora flowers is limited by their low stem mechanical strength, but the underlying mechanism of this low strength is poorly understood. In this study, two P. lactiflora cultivars with distinct stem mechanical strengths (Chui Touhong with low stem mechanical strength and Da Fugui with high stem mechanical strength) were used as test materials. The xylem development was examined at the cellular level, and the phloem conductivity was analyzed by evaluating phloem geometry. The results showed that the secondary cell wall formation of the xylem of Chui Touhong was affected primarily in fiber cells but was affected little in vessel cells. The formation of the secondary cell walls in the xylem fiber cells of Chui Touhong was delayed, resulting in longer and thinner fiber cells with a lack of cellulose and S-lignin in the secondary cell walls. Moreover, the phloem conductivity of Chui Touhong was lower than that of Da Fugui, and more callose was accumulated in the lateral walls of the phloem sieve elements of Chui Touhong. Consequently, the delayed deposition of the secondary cell walls of the xylem fiber cells was the main factor leading to the low stem mechanical strength of Chui Touhong, and the low stem mechanical strength was closely related to the low conductivity of sieve tubes and extensive callose accumulation in the phloem. These findings provide a new perspective on enhancing P. lactiflora stem mechanical strength by targeting single cell level, and lay the foundation for future works on the correlation between phloem long-distance transport and stem mechanical strength.
白芍切花的品质受到其茎机械强度低的限制，但这种低强度的潜在机制尚未得到充分理解。本研究以两个茎机械强度差异明显的白芍品种（翠头红，茎机械强度低；大富贵，茎机械强度高）为试验材料。在细胞水平上研究木质部的发育，并通过评估韧皮部的几何结构来分析韧皮部的导度。结果表明，翠头红木质部次生细胞壁的形成主要影响纤维细胞，而对导管细胞影响较小。翠头红木质部纤维细胞次生细胞壁的形成被延迟，导致纤维细胞更长、更细，次生细胞壁中缺乏纤维素和 S-木质素。此外，翠头红的韧皮部导度低于大富贵，且翠头红韧皮部筛管侧壁积累了更多的胼胝质。因此，木质部纤维细胞次生细胞壁的延迟沉积是导致翠头红茎机械强度低的主要因素，而茎机械强度与筛管导度低和韧皮部胼胝质广泛积累密切相关。这些发现为通过针对单个细胞水平来提高白芍茎机械强度提供了新的视角，并为未来研究韧皮部长距离运输与茎机械强度之间的相关性奠定了基础。
