金花茶组植物嗜钙与嫌钙机制的比较研究

Sect. Chrysantha was named as ‘The Queen of the Camellia Group’ because it is the only group with yellow flowers in the genus Camellia, which brings the worldwide attention in the botanical and horticultural community. This section show a high degree of specificity to the soil environment. For 18 species of this section in ‘Flora of China’, 11 species are calciphile which occur only on calcareous soils, while the rest of 7 species are calcifuge found only on acidic soils. Previous studies mainly focus on population ecology, reproductive ecology and conservation genetics of this section, while its adaptive mechanism to different soil types was not yet understood. Therefore, this project intends to study the element background values of soils and plants of this section, calcium forms and distribution (subcellular fractions) of leaves, response characteristics of seedlings to exogenous Ca2+, root rhizosphere soil organic acid secretion and nutritional limitation of calcifuge in calcareous soils , so as to reveal the adaptive characteristics of this section on different soil types, and clarify the adaptive mechanism of calciphile to high calcium environment and calcifuge exclusion from limestone soils. The results will help to understand the formation and adaptation mechanism of habitat diversity in sect. Chrysantha, and provide scientific basis for biodiversity conservation of this precious group.

金花茶组植物是山茶属中唯一开黄色花的类群，被誉为“茶族皇后”，引起了国内外植物学界和园艺学界的广泛关注。该组植物对土壤环境具有高度的专一性，《中国植物志》记录的18种金花茶中（含变种），11种分布在钙质石灰土，为嗜钙型金花茶；其余7种分布于酸性土，为嫌钙型金花茶。前期的研究主要集中在种群生态学、生殖生态学和保护遗传学等方面，而关于该组植物对不同类型土壤的适应机制还不了解。为此，本项目拟通过研究金花茶组植物与土壤的元素背景值、叶片钙形态及分布部位（亚细胞组分）、幼苗对外源Ca2+的响应特征、根际土壤有机酸的分泌量以及嫌钙型金花茶在钙质土上的营养限制等，从植物营养角度揭示金花茶组植物对不同类型土壤的适应特征，探讨嗜钙型金花茶对高钙环境的适应机制，分析嫌钙型金花茶的避钙机理。研究结果将有助于深入认识金花茶组植物生境多样性的形成及适应机制，为这一珍贵类群的生物多样性保育提供科学依据。

本项目通过研究金花茶组植物与土壤的主要营养元素含量特征及其相互关系、叶片钙形态分布特征、两种类型金花茶对不同土壤条件（酸性土和石灰土）的适应性、不同Ca2+浓度对两类金花茶光合特性、生理指标、叶片超微结构的影响、以及不同钙浓度下两类金花茶的转录组测序分析，揭示了金花茶组植物对不同土壤类型的适应特征，探明了喜钙型金花茶对高钙环境的适应机制以及嫌钙型金花茶的厌钙机理。结果表明：（1）与非岩溶区嫌钙型金花茶相比，岩溶区喜钙型金花茶根部土壤pH值、有机质、N、P、Ca、Mg、Fe、Mn含量较高，而K含量较低。（2）岩溶区喜钙型金花茶根、茎、叶Ca、P含量，茎、叶Mn含量均显著高于非岩溶区嫌钙型金花茶；且根、茎、叶P，茎Ca、茎Mn与土壤中相应元素含量存在显著正相关关系，推测土壤中Ca、P、Mn三种元素对该组植物的生长具有重要影响。（3）喜钙型金花茶叶片在高钙土壤中能形成草酸钙晶体或难溶性的硅酸钙沉淀以降低细胞内Ca2+的浓度，从而适应高钙环境；嫌钙型金花茶不能在石灰土上正常生长，这与其叶片P和Fe缺乏无关，可能是高钙引起的根系钙毒害。（4）高Ca2+浓度下嫌钙型金花茶的叶片细胞结构遭到破坏，光合能力显著降低；而喜钙型金花茶对高Ca2+浓度并不敏感，其适应高钙的生理机制可能与叶片较高的可溶性糖含量有关。研究结果将有助于深入认识金花茶组植物生境多样性的形成及适应机制，为这一珍贵类群的生物多样性保育提供科学依据。