茶树叶片氟亚细胞分布及其与细胞壁结合特性的研究

茶树具有较强的聚氟能力,叶片是主要聚集部位。为探讨茶树叶片聚氟的特性,分析了茶树叶片中氟的亚细胞分布,氟与细胞壁结合的可能方式。结果表明,3个品种茶树叶片中氟都主要分布于细胞壁(39.74%~56.49%),其次分布于可溶性组分(28.35%~37.32%)。果胶和半纤维素组分聚集了细胞壁90%以上的氟,是细胞壁富集氟的主要组分。细胞壁中的氟与Ca、Mn和Al等金属离子含量具有显著的正相关。甲基化和酯化处理能显著降低细胞壁中F、Mg、Fe、Ca、Mn、Al离子含量,而纤维素酶、果胶酶酶解处理对细胞壁中F、Fe、Ca、Mn、Al离子含量影响较小。说明细胞壁中-NH2和-COOH基团在氟与细胞壁结合中起着重要作用,而果胶和纤维素分子链的大小对结合氟影响不大。因此,茶树叶片细胞壁和可溶性组分是氟重要累积部位,二者的区隔化作用降低了氟毒害;氟可能与细胞壁中-OH、-NH_2和-COOH以氢键形式结合或者与细胞壁中金属离子以离子键结合而被固定在细胞壁中。

Fluorine Subcellular Distribution and Its Combining Characteristics with Cell Wall in Tea Leaves (Camellia sinensis)

Tea plant (Camellia sinensis) is a hyper-accumulator of fluorine (F) and its leaves are the main accumulating tissue. In this paper, the F subcellular distribution and its binding characteristics with cell wall in tea leaves were investigated to explore the characteristics of F accumulating in tea leaves. The results showed that most of the F was distributed in the cell wall (39.74％-56.49％) and soluble fraction (28.35％-37.32％) of leaves. Pectin and hemicellulose are the main components of F enrichment and accumulated more than 90％ of F in cell wall. There is a significant and positive correlation between Mn2+, Ca2+, Al3+ and F. The contents of F and metal elements (Mn2+, Fe3+, Ca2+, Mn2+, Al3+) reduced significantly in methylation and esterification cell wall while changed little in enzymolysis cell wall. These suggested that -NH2 and -COOH might play an important role in the combination of F and cell wall, while the molecule weights of pectin and cellulose played little role. Cell wall and soluble fraction are the main sites to store F where F might be combined with -OH, -NH2 and -COOH in the form of hydrogen bonds or with metal elements in the form of ionic bonds. F might be fixed in cell wall and vacuolar as the main defense mechanism of tea plant against F toxicity.