Preliminary Study on Floral Syndroma and Breeding System for Five Species of Rehmannia(Scrophulariaceae)
CHENG Yongqin;ZHAO Jianhua;HAN Kai;ZENG Shuyun;HUANG Jing;LIU Zhanlin;Key Laboratory of Resource Biology and Biotechnology in Western China,Ministry of Education,College of Life Sciences,Northwest University;
Reproduction isolation is the basis of species preservation and divergence,but little is known about the breeding system of Rehmannia.We studied the floral syndroma and reproductive characteristics of the five Rehmanniaspecies(R.chingii,R.piasezkii,R.henryi,R.glutinosa,R.solanifolia)through investigating the following indices in field:flowering dynamics of natural populations,floral morphologies of flower organs,nectar volume and sugar concentration,out-crossing index,pollen-ovule ratio,pollination and bagging experiment.Our results indicate that:(1)Rehmanniaspecies flowers are hermaphroditic.The flowering duration of a single florescence was 5-7days,and the whole population flowering duration was 40-60 days.There are distinct difference among the five Rehmanniaspecies in inflorescence types,floral characteristics,flower color,pollen amounts and P/O values.We found that R.solanifolia were pollen abortion.(2)The evidence of the out-crossing index,pollen-ovule ratio and hybridization experiment supported that the breeding system of Rehmannia was belonged to cross pollination system,partially self-compatible,with no apomictic ability,and pollinators required.We also found there was vegetative reproduction in Reh mannia,especially in R.glutinosaand R.solanifolia.(3)There are nectaries on the base of Rehmanniacorolla and they can produce nectar with higher concentration of sugar,and this also supports the existence ofpollinators.However,we did not observe any effective pollinators in Rehmanniaspecies except in R.glutinosa with bees,which might be due to the scattered individual,isolated habitats and the bad weather conditions during pollination observation.Longer flowering duration could compensate for the insufficiency of pollinator visits.According to our results,we suppose that the different flowers display offive Rehmannia species possibly attracting distinct pollinators,together with genetic,geographic and ecological isolation,results in the differentiation of the breeding system in Rehmanniaspecies.
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