Study On The Time And Location Of Reproductive Barriers And Endogenous Hormone Changes In The HetSI Reaction Of The Plumbago Auriculata Lam.

Heterozygous self-incompatibility(Het SI)is considered to be the most effective reproductive strategy for avoiding self-fertilization.Due to its unique heterostyly phenomenon and a series of corresponding flower organ polymorphism,pollen can make accurate cross-fertilization between different flower types,since Darwin systematically summarized this wonderful feature,academic community has a long history of relevant research.Although scholars began studied Het SI phenomenon from 1877,and put forward some interesting hypothesis and inference,up to now,no matter the experimental materials or results are far less than homotype self-incompatibility(Hom SI)research.In particular,the Het SI reaction mechanism still lacks detailed description and direct evidence.Some scholars believe that the physiological and biochemical reaction in the process of fertilization may explain the observed phenomena in Het SI process,because reproductive barriers are often associated with some physiology reactions like identification and development of pollen and style in fertilization.Therefore,this research choose the Plumbago auriculata Lam.as the research material,which is considered as one of the best illustration materials to study Het SI mechanism,this plant has a typical heterostyly phenomenon and previous research has proved its strict self-incompatibility.However,the time and location of reproductive barriers during its self-pollination process is not clear,and there is still no report on the research about physiological mechanism of incompatibility.Based on the premise that the pollen and stigma of Plumbago auriculata Lam.have no self-disturbance,this study observed the style in the self-fertilization and hybridization types of artificial pollinated Plumbago auriculata Lam.through fluorescence microscopy techniques,and determined their endogenous hormones,then found critical time and location of reproductive barriers and endogenous hormone change rule in the Het SI process of Plumbago auriculata Lam.The research results can enrich the types of Het SI plant materials and help to systematically understand the physiological mechanism of Het SI reaction.The results are as follows:(1)Plumbago auriculata Lam.type-two pollen has a extremely high vitality,and it can germinate quickly in all media.There is no significant difference between pollen germination rate of long and short style.After testing,type-two flower’s stigma also has a high pollination availability.The above conclusions illustrate that there is no reproductive barrier in stigma and pollen itself.(2)Although Plumbago auriculata Lam.pollen can germinate in vitro environment,pollen tube can’t grow normally.After 10 minutes,pollen has no activity,the pollen tube it grows is twisted,slender,which began to rupture over time.(3)The Het SI reaction barrier of Plumbago auriculata Lam.appeared in the identification process of the stigma surface in 0-1 hour after pollination.After 1-2 hours,the pollen with compatibility pollination was firmly attached to the stigma,while the the pollen with incompatibility pollination can’t attach to the stigma normally,and no pollen tube was observed inside the stigma.Over time,both two types of pollen with compatibility pollination can be fertilized,but the pollen with incompatibility pollination still can’t attach to the stigma after 32 hours.(4)After treatment with different artificial pollination,the IAA,GA3,ZR and ABA content in all pollination combinations presented a relatively stable state of slow increase over time,and there was no significant difference between different artificial pollination treatments.Although the difference of content appeared in individual treatments,the hormone content did not fluctuate significantly over time.Therefore,the level of endogenous hormone in the style may not be the key factor of self-incompatibility.Above all,there is no congenital reproductive barriers existed between Plumbago auriculata Lam.type-two pollen and stigma.The self-incompatibility reaction appeared in the stigma surface in 0-1 hour after pollination.The pollen with incompatibility pollination can’t attach to the stigma normally.The endogenous hormone in the style is not the key substance of self-incompatibility reaction process,the self-incompatibility reaction may be regulated by other key signal substances.