| Neolamarckia cadamba belongs to the Neolamarckia Rubiaceae.It is a native fast-growthhard-wood tree species in tropical and subtropical regions of China.Neolamarckia cadamba has been widely used in the production of industrial timber forest and interior decoration.Its bark and leaves are rich in bioactive substances such as cadamine and so on.The medicinal effect of Neolamarckia cadamba is obvious.At the same time,as an excellent tree species for landscaping and feed,Neolamarckia cadamba has been widely popularized.Although there have been a lot of reports on the cultivation,cultivation techniques and the development and utilization of medicinal components,the studies on pollination biology,especially the biological characteristics of pollen have not been reported.In order to reveal the biological characteristics of Neolamarckia cadamba pollen,this study studied the flowering period,artificial pollination,pollen viability and sucrose concentration of Neolamarckia cadamba population in North of Qilin,South China Agricultural University of Guangdong Province,and studied the flowering period,artificial pollination,pollen viability and sucrose concentration of Neolamarckia cadamba.The effects of boric acid concentration,storage time and culture time on pollen germination rate and pollen tube elongation were studied.The morphology of pollen was observed by electron microscope.The basic data of pollen biological characteristics were obtained.It provides a theoretical basis for improving the cross breeding efficiency of Neolamarckia cadamba.The main findings are as follows:1.The Biological characteristics of flowering and Pollen of Neolamarckia cadamba(1)The flower bud color changed gradually from cyan to yellow,and the stigma on the surface of the bud extended to form globular flower with the flower bud at a single flowering stage of 6 h to 62 h.The anther and stigma of Neolamarckia cadamba were wrapped in a cylindrical shape,the upper part of the style,the inside of the stigma bent inward to the bottom of the anther,and the back of the stigma was opposite to the direction of anther dehiscence.The stigma of Neolamarckia cadamba can be divided into three stages.At the initial stage of pollen opening,the stigma is slightly protruding and golden yellow.In the middle stage of pollen blooming,the surface of stigma was exposed to wet secretions,the synaptic glandular cells spread out,the stigma curled outward,and the top of stigma gradually faded.During the anaphase of pollen decline,the stigma of Neolamarckia cadamba was opened and rolled downward,and the stigma wilted gradually and began to wither.(2)Before flowering,the stigma of Neolamarckia cadamba had the ability to impart,the synaptic glandular cells on the surface of the stigma were extended and mucus produced.About 70% of the stigmas from 24 hours before anthesis had the ability to impart,and kept the pollinability for 4 days until withered.(3)Neolamarckia cadamba is a monoecious plant,which is mainly pollinated by self-pollination and assisted by cross-pollination.When artificial pollination was carried out,the optimum time of pollination should be 24 hours after flowering of Neolamarckia cadamba.2.Determination of Pollen viability and influencing factors of Pollen germination in Neolamarckia cadamba(1)The highest peak value of pollen activity appeared on the first day of flowering,which was 21%,and the pollen activity was basically inactivated on the third day after anthesis.Pollen germination rate of Neolamarckia cadamba was influenced by sucrose concentration,pollen storage time,boric acid concentration and culture duration.Low concentration of boric acid and sucrose promoted pollen germination of Neolamarckia cadamba respectively.(2)The increase of concentration after reaching the optimum concentration inhibited the germination of Neolamarckia cadamba pollen.The germination rate of Neolamarckia cadamba pollen cultured at 3% sucrose concentration for 4 h reached the highest in this experiment,which was 71.42%.The pollen tube length of yellow Neolamarckia cadamba pollen cultured at 5% sucrose concentration for 48 h reached the maximμm value of this experiment,which was 346.01 μm.3.Micromorphological characteristics of Pollen of Neolamarckia cadambaThe results of electron microscopic observation showed that the pollen of Huangliangmu was olive-shaped.The pollen size was about 15.10 μm×7.95 μm,under electron microscope.The mean(P)of polar axis length was(17.04±0.91)μm,.The mean(E) length of equatorial axis was(9.29±0.89)μm,.The ratio of polar axis length to equatorial axis length of pollen is 1.84,and the length of germination ditch is(12.11±1.06)μm.Pollen exine without special bulge and villi,with obvious reticulate pattern,consisting of raised reticulated ridges and mesh of different sizes. |
