橙花瑞香的繁殖特性研究

Reproductive characteristics of Daphne aurantiaca

关键词:  橙花瑞香, 繁殖, 传粉生物学, 扫描电镜, 坐果率

Key words:  Daphne aurantiaca, reproductive, pollination, scanning electron microscope, fruit setting rate

摘要:

瑞香属植物具有重要的药用和观赏价值,在中国资源丰富,但自然条件下低坐果率限制了该属植物的进一步开发和利用。该研究以橙花瑞香为对象,通过对其有性繁殖及传粉特性的研究,探索其自然坐果率低的原因,内容包括花部特征的测量分析,MTT染色法测定花粉活性,联苯胺-过氧化氢法测定柱头可授性,扫描电镜观察柱头、花粉的形态,传粉者观察,通过花粉胚珠比(P/O)和人工授粉实验推测橙花瑞香的繁育系统类型。结果表明:橙花瑞香的花部结构特殊,管状小花,花药两轮,雌雄蕊分离。花开后的花粉具有活性,柱头具有可授性,扫描电镜下,柱头和花粉的结构没有发育异常,且柱头上有花粉落置。橙花瑞香的传粉者主要是夜间访花的蛾类,访花频率低。P/O及人工授粉实验表明橙花瑞香的繁育系统为专性异交。橙花瑞香的坐果率非常低,自然坐果率为1.4%,人工异花授粉为23.3%,低坐果率可能是受其开花量大、异花花粉限制、资源限制以及花部结构等因素的影响。

Abstract:

Daphne has important medicinal and ornamental values and it is rich in resources in China. Low fruit setting rate is a feature of the genus, and limits its further development and utilization. As the machanism for low fruit setting is unclear and few related studies have been carried out, especially in China, almost no one has carried out such relevant work. We explored the reasons for low natural fruit setting rate of D. aurantiaca, using D. aurantiaca as research material, through studying its sexual reproduction and pollination characteristics, including the measurement of floral traits, the detection of pollen viability by MTT solution and stigma receptivity by benzidine-H₂O₂ solution, observation of stigma and pollen morphology by scanning electron microscope(SEM), and survey the visit rates of pollinators. The breeding system was tested by pollen ovule rate(P/O)and artificial pollination experiment. The results showed that pollen grains of D. aurantiaca had activities and stigmas had receptivities, and stigma and pollen developed normally through the SEM observation, which indicated that both male and female functions were normal. The flower structure of D. aurantiaca was special, flowers were very small, tubular structure, stigma-anther separation, with anthers consisting of two wheels arranged in the middle and top of corolla tube while stigma in the base of corolla tube. During the day time we did not see any effective visitors, and at night we found the main pollinator of D. aurantiaca was moths, with low visiting rate. We only found two moths in the whole period of the visitor observation, and one moth visited three flowers and the other visited two flowers in the same plant. Both P/O and artificial pollination experiments showed that the breeding system of D. aurantiaca was obligated out-crossing and self-incompatible. The fruit setting rate of D. aurantiaca was very low, only 1.4% in natural pollination and 23.3% in artificial cross-pollination. Its low fruit setting rate may be restricted by the large amount of flowers per plant, the inbreeding depression, the shortage of outcross pollen grains, resource limit and the influence of the flower structure. This study can provide theoretical basis for the utilization, preservation and expansion of D. aurantiaca resources.