绞股蓝为葫芦科绞股蓝属的重要药用植物，因能合成和积累人参皂苷类物质而被誉为“南方人参”。由于其种植区广，有望成为人参的代用品。作为多年生草质藤本，绞股蓝地上部分的生活期不足一年，其藤蔓在入冬枯死前，从空中垂下，顶芽发育为节间粗短的变态芽。变态芽长入土中，并分化出多个侧芽，越冬后萌发成新苗。我们称这一现象为茎端入土无性繁殖。这一罕见的无性繁殖现象一直被绞股蓝研究者所忽视。我们推测变态芽是由特定的环境因子所诱导，且体内可能发生两类生理学逆转：生长的向性由负的向地性转向正的向地性，发育阶段由成熟阶段恢复到幼态阶段。为此，本项目拟根据对自然生境中绞股蓝这种无性繁殖现象的观察和人工气候室摸拟实验，发现诱导变态芽形成的主要环境因子，建立绞股蓝顶端入土无性繁殖的实验体系，并采用实验形态学、生理学和分子生物学等方法，揭示绞股蓝这一无性繁殖的生理学机制和生态学意义，并为发展绞股蓝高效栽培技术提供理论依据。

Jiao-Gu-Lan (Gynostemma pentaphyllum) is an important medicinal plant in the Cucurbitaceae family. This medicinal plant is called “Southern China Ginseng” because it produces a high content of ginsenosides. Its southern nation-wide farming is expected to substitute Ginseng in the future. Although it is a perennial climbing herb, its above-ground organs only grow one season because they completely senesce prior to winter. There is a specific development feature during senescense, during which stems grow gravitropically and each shoot apex develops into a big adventitious bud. All adventitious buds gravitropically grow into soil and develop into multiple auxillary buds, from which new plants will start to grow in the new growth season. Here, this phenomenon is defined as “Gravitropism of Shoot Apex Propagation (GSAP)” Unfortunately, this GSAP has never been studied. Our hypothesis is that this growth phenomenon is induced by environmental factors. In addition, we hypothesize that there are two physiological reversions associated with this GSAP: 1) a change from negative gravitropism to garvitropism and 2) development from adult phase to juvenile adventurous buds. In this project, we propose to complete the following 6 experiments, 1) investigation and recording of GSAP in the field, 2) plant growth in growth chamber to testing induction factors of GSAP, 3) microscopical observation and anatomic characterization, 4) observation of amyloplast distribution and IAA immunolocalization in cells, 5) analysis of plant hormones during GSAP, 6) analysis of gene expression involved in mRNA and miRNA. The outcome will elucidate the physiological mechanism and ecological significance of GSAP, and will be important to develop new biotechnology to enhance propagation for Jiao-Gu-Lan agriculture.