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1、濒危植物长柄双花木的花部综合特征与繁育系统肖宜安1 ,2 何 平13李晓红2(1西南师范大学生命科学学院,重庆北碚 400715) (2井冈山师范学院生命科学系,江西吉安 343009)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(Disanthus cercidifoliusMaxim. 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67 d ,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12 d。单花花期依其
2、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4955 d ,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1 250 ,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。关键词 繁育系统 遗传变异 杂交指数 花粉-胚珠比 长柄双花木FLORAL SYNDROME AND BREEDING SYSTEM OF THE ENDANGERED PLANT DISANTHUS CE
3、RCIDIFOLIUSMAXIM. VAR.LONGIPESXIAO Yi-An1 ,2 HE Ping13and LI Xiao-Hong2(1School of Life Science, Southwest China Normal University , Chongqing400715,China)(2Department of Life Science, Jinggangshan Normal College , Jian , Jiangxi343009,China)Abstract We conducted a field investigation of the floral
4、syndrome and breeding systemofDisanthus cercidi2 foliusMaxim. var.longipesH. T. Chang , an endangered plant species , in both artificial and natural popula2 tions in Mt. Jinggang , a National Reserve in Jiangxi , China. We describe our findings below. There are two inflorescences , often on opposite
5、 axillaries at the same node , each inflorescence with two opposite bisexual flowers with no pedicels. Flowering lasted 5 to 6 days. On the dayof 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
6、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
7、circle” surrounding the stigma when the anthers all dehisce. The flowering span among populations is 49 - 55 days. The flowering processfor one flower of this species can be divided into four periods by the flower morphology and dehiscence :“Pre-dehiscence”in which two fila2 ments stretch out with n
8、o dehiscence ;“Initial dehiscence” after two daysof flowering , one or two anthers de2 hisce ;“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 t
9、o 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 or2 gans within the same flower. It is protandrous with an
10、 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 Crudens criteri2 on , the breeding sys
11、tem 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 ,
12、 bagged and free pollinated. In the treatments where flowers were emasculated , unbagged and free pollinated , or unemasculated , unbagged and free pollinated , or emascu2 lated , bagged and hand self-pollinated , the inflorescences were able to produce some seeds. In the treatments of emasculation
13、, bagging and hand geitonogamy or hand cross-pollination , the inflorescences was able to pro2 收稿日期: 2003203225 接受日期: 2003208203基金项目:国家自然科学基金项目(30070080)3 通讯作者Author for correspondence E-mail : heping 植物生态学报 2004 , 28 (3)333340 Acta Phytoecologica Sinicaduce more seeds , but its production ratio was
14、 still low , ranging from 28.50 % to 45.01 %. There was no ag2 amospermy , 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 numb
15、er of alleles per locus (A) is 1.63 , and the mean effective number of alleles per locus is 1.55. TheGstis 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
16、ofD. cer2 cidifoliusMaxim. var.longipesH. T. Chang. Key words Breeding system , Genetic differentiation , Outcrossing index , Pollen-ovule ratio ,Disanthus cer2 cidifoliusMaxim. var.longipesH. T. Chang植物花的综合特征包括两个方面:花部构成(Floral design)和花的开放式样(Floral display)。花部构成主要包括花的结构、 颜色、 气味、 分泌物质类型 及其产量等单个花的所有特征;花的开放式样则指花在某时间开放的数量、 花在花序上的空间排列状 况等,是花在种群水平上的表现特征。 繁育系统是指控制种群或分类群中异体受精或 自体受精相对频率的各种生理、 形态机制(Heywood ,1979) ,在决定植物的进化路线和表征变异上起着重要作用(Grant ,1981) ,是种群
