桃儿七种子解剖结构及其萌发生长期形态特征

为探明种皮和胚乳是否是限制桃儿七种子萌发的主要因素，利用组织切片和显微技术，对桃儿七种子及其不同萌发期（1、7、14、21、28 d）解剖结构和播种后一定时期内（7~210 d）的植株生长形态进行观察。桃儿七种子由种皮、胚乳和胚构成。种皮包括外种皮和内种皮，外种皮致密规整，由外至内分别为栅状石细胞和表皮层细胞，内种皮由5~6层海绵细胞组成。胚乳占种子体积的绝大部分，包括珠孔胚乳和外胚乳。胚由胚根、胚轴和子叶组成，被致密种皮、多层珠孔胚乳和外胚乳包围。萌发期1~7 d胚根和胚轴开始伸长，7~14 d两片子叶分离，14~21 d胚根突破珠孔胚乳和种皮，21~28 d胚根、胚轴和子叶继续扩张伸长。种子播种210 d后可平均形成3片功能真叶和5条不定根。致密种皮（物理休眠）和多层胚乳（机械休眠）是限制桃儿七种子萌发的两个主要因素。

Anatomical Structure of Seed and Morphological Character at Different Germination Stages of Sinopodophyllum hexandrum

To reveal whether the testa and endosperm are main factors restricting the seed germinationof Sinopodophyllum hexandrum， anatomical structure of seed in different germination stages（1， 7， 14， 21 and 28 d） of S. hexandrum were observed by using the tissue sectioning microscopy， and morphological characteristics of plants were investigated after the germination seeds sowing 7-210 d. The seed of S. hexandrum was composed of testa， endosperm and embryo. The testa contained episperm and endopleura， the episperm was compact and regular and it was composed of palisade cells and epidermal cells from outside to inside， and the endopleura was composed of 5-6 layers sponge cells. The endosperm accounted for most of the seed， included micropylar endosperm and outer endosperm. The embryo consisted of radicle， hypocotyl and cotyledons， surrounded by the compacted testa， multilayer-micropylar endosperm and outer endosperm. During the germination stage， the radicle and hypocotyl began to elongate from 1-7 d， two cotyledons separated from 7-14 d， the radicle broke through the micropylar endosperm and testa from 14-21 d， the radicle， hypocotyl and cotyledons continued to expand and elongate from 21-28 d. 3 function leaves and 5 adventitious roots were formed on average after seeding for 210 d. The compacted testa（physical dormancy） and multilayer endosperm（mechanical dormancy） were the two main factors that restricted seed germination of S. hexandrum.