桃儿七种子休眠解除过程中细胞壁代谢及种皮超微结构的变化北大核心CSCD

为探究低温层积过程中桃儿七种子细胞壁代谢及种皮超微结构与休眠解除的内在联系，该研究通过低温层积解除桃儿七种子休眠，分析休眠解除过程中种子不同部位细胞壁组分及相关代谢酶的变化，同时利用扫描电镜对种皮的超微结构进行观察。结果表明，(1)桃儿七种皮主要由角质层、栅状石细胞层及海绵组织层3层构成，在层积过程中，种皮内部的海绵组织逐步疏松膨胀，种皮表面破损加剧；(2)种子不同部位的细胞壁组分具有明显差异，整个层积过程中，种胚、种皮和胚乳中的纤维素含量均在层积中期(45 d和60 d)降至最低，3个部位的纤维素酶活性在层积中期对应升高；种胚和种皮内的半纤维素含量均在层积中期显著下降，种皮中甘露聚糖酶活性和木糖苷酶活性在层积中期时相应达到最大；3个部位的果胶含量均在层积后期(75 d和90 d)时显著下降，而种皮和胚乳中多聚半乳糖醛缩酶活性也在层积后期相应升高；(3)种胚和胚乳内过氧化物酶活性在层积75 d和90 d时明显下降，而SOD活性在此时显著上升。(4)种子不同部位3种木质素单体的组成比例具有明显区别，同时3种木质素单体含量均随层积时间的延长而显著降低，且胚乳和种皮中的S-木质素含量对种子萌发存在显著的负向影响关系。研究认为，在低温层积过程中，桃儿七种子内细胞壁组分纤维素、半纤维素及木质素的逐步酶解，活性氧作用下的细胞壁松弛以及海绵组织层的疏松膨胀和种皮的破裂，破坏了细胞壁的刚性结构，促使种子机械束缚力降低，吸水性能提高、胚根生长能力增强，最终导致其休眠解除。

Changes in Cell Wall Metabolism and Seed Coat Ultrastructure during Dormancy Release in Seeds of Sinopodophyllum hexandrum(Royle)Ying

To investigate the relationship between the cell wall metabolism and the ultrastructure of the seed coat and the release of dormancy during the process of low-temperature lamination, this study was carried out to analyze the changes in cell wall components and related metabolic enzymes in different parts of the seeds during the release of dormancy by low-temperature lamination, and to observe the ultrastructure of the seed coat by scanning electron microscopy. The results showed that the seed coat of Sinopodophyllum hexandrum mainly consisted of three layers, namely the cuticle layer, the fenestra cell layer, and the spongy tissue layer, and during the lamination process, the spongy tissue inside the seed coat gradually loosened and swelled, and the breakage of the seed coat surface intensified; the cell wall fractions of different parts of the seeds were significantly different, and the cellulose content of the seed embryo, seed coat, and endosperm all decreased to the lowest level at the middle of the lamination process (45d and 60d). The cellulose content in the seed embryo and seed coat decreased significantly at mid-lamination (45d and 60d), while the mannanase and xylanase activities in the seed coat reached their maximum at mid-lamination. The results of stepwise regression analysis indicated that S-lignin in the endosperm and seed coat had a significant adverse effect on seed germination; peroxidase activity in the seed embryo and endosperm decreased significantly at 75 and 90 d of lamination, while S-lignin activity in the seed coat and endosperm decreased significantly at 75 and 90 d of lamination. The peroxidase activity in seed embryo and endosperm significantly reduced at 75 and 90 d of lamination, while SOD activity increased significantly. The study concluded that the gradual enzymatic degradation of cellulose, hemicellulose, and lignin in the seeds of Sinopodophyllum hexandrum, the relaxation of the cell wall under the action of reactive oxygen species, and the loosening and swelling of the spongy tissue layer and the rupture of the seed coat during the familiarization process destroyed the rigid structure of the cell wall, which led to the reduction of the mechanical binding force of the seeds, the increase of water absorption and the enhancement of the endosperm growth capacity, thus eventually leading to the release of its dormancy.