鱼腥草的花粉活力及雌雄配子体的发育

Pollen Viability and Male and Female Gametophyte Development in Houttuynia cordata Thunb.

为深入了解鱼腥草有性繁殖特性及为鱼腥草杂交育种提供理论依据,以栽培的三年生鱼腥草(Houttuynia cordata Thunb.)为材料,采用I2-KI染色法、培养基培养法、荧光显微镜观察法研究鱼腥草花粉活力;用石蜡切片法观察鱼腥草雌雄配子体的发育过程。结果显示,鱼腥草花粉活力极低,仅I2-KI法检测出鱼腥草花粉活力为3.18%,培养基培养法、荧光显微镜观察法均未测出花粉活力。其雄配子体在早期发育正常,但在二分体时期发现绒毡层解体,最后游离小孢子细胞质逐渐消失,显示出空瘪状态,形状也由近圆形变为不规则形,最终在花粉囊开裂之前小孢子败育。雌蕊心皮3枚,合生成一室,侧膜胎座;直生胚珠,为双层珠被,薄珠心;造孢细胞起源于紧接表皮之下的珠心细胞,造孢细胞直接发育成大孢子母细胞;大孢子母细胞经减数分裂形成线形或T形排列的四分体,靠近合点端的一个四分体细胞形成功能大孢子;功能大孢子经连续3次有丝分裂形成7细胞8核的蓼型成熟胚囊。鱼腥草可能因绒毡层提早解体导致雄性不育,其种子的产生可能来自于无融合生殖。

The aim of this study was to understand the characteristics of sexual reproduction in Houttuynia cordata and provide a theoretical basis for cross breeding. Using a population of H. cordata with three years of cultivation, pollen viability was determined by 12-KI staining, Brewbaker ＆ Kwack culture medium and fluorescence microscopy observation, respectively; the developmental course of male and female gametophytes was observed using paraffin sections. Results showed that H. cordata pollen viability was extremely low, with 12-KI staining showing pollen viability of 3. 18%, and culture and fluorescence microscopy observation unable to measure pollen viability at all. The male gametophyte was normal in early development, but in the dyad period the tapetum cell was disintegrated. The cytoplasm of free microspores gradually disappeared and showed an empty flat shape, the microspore shape changed from suborbicular to irregular. Finally, microspore abortion occurred before pollen sac cracking. A pistil was composed of three united carpels and connated into one Iocular, parietal placentation. The ovule was atropous, double integument and tenuinucellus. Sporogenous cells originated from the nucellar cells immediately beneath the epidermis, and developed into macrosporal mother cells. Macrosporal mother cell meiosis formed linear or Tshaped megaspore tetrads. The large one at the chalazal end was a functional megaspore. The functional megaspore developed into a polygonum type embryo sac.which contained seven cells containing eight nuclei after three times consecutive mitosis. Male sterility may be due to the premature disintegration of the tapetum, and the seed may come from apomixis.