摘要
通过野外观察 ,运用杂交指数、花粉_胚珠比、人工授粉和套袋实验及等位酶电泳等方法 ,对长柄双花木(DisanthuscercidifoliusMaxim .var.longipesH .T .Chang)自然种群和人工种群的开花状态、繁育系统进行了研究。结果如下 :该种单花花期一般 6～ 7d,开花过程中柱头始终高于花药的位置 ,花药散粉具有先后顺序 ,一般 2花药先散粉 ,其余 3花药滞后 1～ 2d。单花花期依其形态和散粉时间可分为 5个时期 :即散粉前期、散粉初期、散粉盛期、凋谢期。种群开花一般历时 4 9～ 5 5d ,但不同地点、年份之间有所差异 ,推测开花持续时间不同主要是环境条件所致。由于其杂交指数大于 4 ,花粉_胚珠比等于 12 5 0 ,结合人工套袋和授粉实验以及等位酶电泳结果可以确定该种的繁育系统属于异交为主 ,部分自交亲和 ,传粉过程需要传粉者。花粉竞争可能是导致该种濒危的主要的生殖生物学原因。
We conducted a field investigation of the floral syndrome and breeding system of Disanthus cercidifolius Maxim. var. longipes H. T. Chang, an endangered plant species, in both artificial and natural populations in Mt. Jinggang, a National Reserve in Jiangxi, China. We describe our findings below. There are two inflorescences, often on opposite axillaries at the same node, each inflorescence with two opposite bisexual flowers with no pedicels. Flowering lasted 5 to 6 days. On the day of anthesis, the styles are longer than the filaments; the length between anthers and stigmas is about 1.02 mm. The color of petals changes from light red to brown. The stigma changes from light green to pale yellow, to brown, and lastly to black. The anthers dehisce in order of priority. Two of the anthers whose dehiscence pattern is longitudinal and synclinal upward always dehisce first, followed by the others. The pollen forms an obvious 'pollen circle' surrounding the stigma when the anthers all dehisce. The flowering span among populations is 49-55 days. The flowering process for one flower of this species can be divided into four periods by the flower morphology and dehiscence: 'Pre-dehiscence' in which two filaments stretch out with no dehiscence; 'Initial dehiscence'-after two days of flowering, one or two anthers dehisce; 'Full dehiscence' is between the third and fifth day when three to five anthers dehisce, and the color of the stigma changes to yellow; and the last period is 'Withering period', that occurs from the sixth to seventh day, when all anthers have dehisced, some have begun to wither, and the color of some stigmata changes to brown or black yellow. The floral diameter is ca. 15 mm. There are both temporal and spatial isolations of male and female organs within the same flower. It is protandrous with an outcrossing index of 4. According to criteria put forward by Dafni, the breeding system of this species can be determined as outcrossing with partly self-compatible and needs pollinators during the pollination. The pollen-ovule ratio (P/O) is 1 250. Based on Cruden's criterion, the breeding system would be termed xenogamy. Based on the results of emasculation, bagging, and artificial pollination studies, the inflorescences of this species produced seeds differently. There are no seeds when the inflorescences are emasculated, bagged and not pollinated and few seeds when unemasculated, bagged and free pollinated. In the treatments where flowers were emasculated, unbagged and free pollinated, or unemasculated, unbagged and free pollinated, or emasculated, bagged and hand self-pollinated, the inflorescences were able to produce some seeds. In the treatments of emasculation, bagging and hand geitonogamy or hand cross-pollination, the inflorescences was able to produce more seeds, but its production ratio was still low, ranging from 28.50% to 45.01%. There was no agamospermy, and outcrossing was the main form of breeding system. This species maintains a relatively high level of genetic variation as compared to an average species. The proportion of polymorphic loci (P) is 62.70%, the average number of alleles per locus (A) is 1.63, and the mean effective number of alleles per locus is 1.55. The G st is only 0.09. The results show that outcrossing is predominant in the breeding system of this species. We conclude that pollen competition may be the major factor leading to the endangered status of D. cercidifolius Maxim. var. longipes H. T. Chang.
出处
《植物生态学报》
CAS
CSCD
北大核心
2004年第3期333-340,共8页
Chinese Journal of Plant Ecology
基金
国家自然科学基金项目 ( 3 0 0 70 0 80 )
关键词
濒危植物
长柄双花木
繁育系统
遗传变异
杂交指数
花粉-胚珠比
Breeding system, Genetic differentiation, Outcrossing index, Pollen-ovule ratio, Disanthus cercidifolius Maxim. var. longipes H. T. Chang
