Flower Structure And Apomixis Characteristics Of Zanthoxylum Armatum 'Tengjiao'

Zanthoxylum armatum 'Tengjiao' is a cultivar of Z.armatum DC.,it's an important plant of oil,spice and Chinese medicinal material.Now,the research on Z.armatum 'Tengjiao'is mainly about the extraction and analysis of its chemical components and the study of its active ingredients,the research on its biological characteristics is very few,so the basic research is weak.To define the apomixis characteristics of Z.armatum 'Tengjiao',perfect the basic knowledge of the structure and function of its flower,a series of related studies on it was conducted in 2016:field investingation,bagging isolation and artificial pollination and bagging experiment etc.were conducted on it at bloom period;its floral structure were dissected and observed under stereomicroscope,and its stigma receptivity was detected by benzidine hydrogen peroxide method,its pollen viability was measured by staining and in vitro culture;megasporogenesis and megagametogenesis were observed by paraffin sectioning technique.The field investigation and sampling site is located in the 4 group of sunshine village in Luomu town,Emeishan City,and the laboratory test is conducted in the laboratory of forestry institute of Chengdu campus of Sichuan Agricultural Uniersity.The main results are as follows:(1)Flower structure and flowering process.The florescence of Z.armatum 'Tengjiao' is from March to April,lasts about 40 days.The majority of Z.armatum 'Tengjiao'(>90%)are female plants,the minority of it are monoecious,very few plants have a small amount of hermaphrodite flowers.The inflorescence of Z.armatum 'Tengjiao' is cymose panicle,axillary or in the top of its lateral branch.The flowers are polygamo,usually unisexual,bisexual flowers are very rare.Male flowers are increasing year by year,they may be abnormal development.The flower shape of Z.armatum 'Tengjiao' changes during flowering.The flowers with one bracteole outside,have 6?9 pieces of tapel arranged in a round.The shape and size of the tapel is basically the same.The female flowers have 2-4 pieces of carpel with joint base and separated upper part,and each carpel has 2 pieces of parallel ovule,one cylindrical style and capitate stigma.The male flowers have 4-7 pieces of stamen with broad elliptic dorsifixed anther.The hermaphrodite flowers usually have less stamens than male flowers or have thin pistil which ovarys are not developed.(2)The development of ovule.The ovule of Z.armatum 'Tengjiao' is anatropous with bitegmic and thick nucellus.The development of its embryo sac belongs to polygonum type.The megasporocyte undergoes meiosis to form a linear tetrad.The megaspore at the chalazal end of the linear tetrad has function,and the other three degenerate.The functional megaspore develops into mononuclear embryo sac,which forms two nucleus embryo sac by mitosis.In the experiment,the polar nucleis of mature embryo sac and the remnant of degenerated embryo sac were seen,but no quad embryo sac and complete eight nucleus embryo sac was seen.During megasporogenesis and megagametogenesis,there is a phenomenon of degeneration which mainly occurs in megasporogenesis.Besides,there was no mature embryo sac before style off.So,the possibility of sexual reproduction in Z.armatum Tengjiao' is very low.(3)Stigma receptivity and pollen viability.During flowering,the stigma receptivity varied with the change of style and stigma.Shortly after flowering,the styles were parallel,the stigma was not obvious and had no receptivity.After that,the styles slowly separated,the stigma gradually became obvious,so it gradually had different degrees of receptivity.When the styles oblique separated and bent to its back,stigma was capitate,stigma receptivity reached to its maximum,60%of the stigmas reached receptivity level 3.At this time,the male flowers were in the pollen dispersal stage.It's not suitable to test pollen viability of Z.armatum 'Tengjiao' by TTC staining.The pollen viability tested by other methods were low.(4)Experiment of isolation with bag.The flowers of Z.armatum 'Tengjiao' isolated by bag can still produce fruits with seeds,it is indicated that Z.armatum 'Tengjiao' can reproduct by apomixis,and the formation of endosperm is autonomous.Its fruit setting rate was 24.21%.However,because of the long flowering period,the time of isolation by bag was up to 26 days,which may had influence on fruits development.Some other factors can also lead to flowers or fruits drop.Therefore,apomixis fruit setting rate of Z.armatum'Tengjiao' should be more than 24.21%.(5)Fruit and seed.The fruit of Z.armatum 'Tengjiao' is follicle,each fruit containing 1-2 seeds.When there is 1 seed in a fruit,the seed is ovoid,which developed by one of the ovarys in an ovule.When there is 2 seeds,the seeds are domed,which developed by the whole two ovarys in an ovule.The seed setting rate of all the treatments were low(9.44%?26.37%)and the majority seeds(67.30%?69.21%)were ovoid seeds,which indicated that the abortion of the ovule was universal,that is to say,there only one ovule developed into seed in many ovarys.The order of 100 Fresh fruits' weight of each treatment was:natural pollination A>artificial pollination and bagging>natural pollination B>isolation with bag.Therefore,it is speculated that pollen may promote the growth of fruit.