绞股蓝正常茎转变为根状茎的形态结构和内源激素含量变化

绞股蓝(Gynostemma pentaphyllum)茎端具有在秋季钻入土中发育为根状茎以越冬和增殖的现象。观察绞股蓝根状茎的形成过程及其组织结构特点，并检测根状茎不同发育阶段和不同节段的内源激素含量。结果表明，正常茎端首先发育为膨大的变态茎并钻入土中，在土中发育成根状茎并进行增殖，腋芽或侧枝的增殖倍数为2.28，来春可萌发出多株新苗。正常芽、变态茎和根状茎的基本结构相似，但后两个阶段的淀粉鞘细胞、髓和髓射线细胞中含有丰富的淀粉粒。生长素、赤霉素和茉莉酸的含量在正常茎端中最高，变态茎端次之，根状茎最低。三种激素在各茎端从芽尖段、弯曲段、膨大段至稳定段的含量总体表现为先升后降趋势。三种激素在变态茎的弯曲段含量明显升高，并在膨大段达到最高值，而生长素在根状茎的弯曲段含量最高，反映它们对相应节段发育的促进作用。

Changes of Morphological Structure and Phytohormone Contents during the Aerial Stem-to-Rhizome Transition in Gynostemma pentaphyllu

The apex of aerial stem of Gynostemma pentaphyllum could drill into the ground in autumn then develop into rhizome with proliferated buds underground to survive overwintering. The formation progress and tissue structure of rhizome were observed and the phytohormone contents of IAA, GA and JA in different parts of three stages during aerial stem-to-rhizome transition were examined in this paper. The results showed that the aerial stem apex developed into swell modified stem firstly, and then drilled into ground where it developed into rhizome. The rhizome proliferated average 2.28 new axillary buds or lateral branches, which sprouted in the upcoming spring. The basic structure of aerial stem, modified stem and rhizome was the same, with the latter two stems contained abundant starch grains in the cells of starch sheath, pith and pith ray. The highest contents of IAA, GA and JA were found in aerial stem apex, the second in abnormal stem apex, and the least in rhizome. The dynamic contents of these phytohomones from the tip section, hook section, swelling section to stable section presented a trend of increasing first and then decreasing. The IAA, GA and JA content ascended at hook section and reached maximum value at swelling section in modified stem, while the IAA had the highest content at hook section in rhizome, which indicated their physiological functions at the corresponding parts.