Study On Pollination Methods And Embryology Of Cremastra Appendiculata(D.Don) Makino

Using Cremastra appendiculata as test material,the seed setting rate of it under different treatments was compared by the treatment of flower thinning degree,pollination period and pollination method.as well as studied the development of capsules,the morphology of seeds(including embryos),seed embryo rate,seed germination rate and of different pollination methods,to establish a suitable method for artificial pollination of C.appendiculata.On this basis,the processes of microspore formation and development of male and female gametophytes,embryogenesis and seed germination were studied to enrich the embryological data of C.appendiculata.The main research results are as follows:(1)Through different treatments of flowering plants,it was found that the number of pollinated flowers had a great influence on the seed setting rate.According to the comprehensive seed setting rate and fruit yield,it is known that the pollination effect of flowering to 10~15 flowers/plant is better;the artificial pollination is carried out during the flowering period(the side opening degree of the flower is more than 90° during the flower opening process),and the seed setting rate is the highest;The seed setting rate under the artificial pollination method is different,and the seed setting rate of the xenogamy is slightly higher than other pollination methods.When a large number of seeds were aggregated into a heap,the seeds of the self-pollination and the geitonogamy were milky white,and the seeds of the xenogamy were light brown;the seeds of thegeitonogamy were the largest;the seeds of xenogamy is the largest ofthe embryo volume,and the volume ratio of seed to embryo is the smallest,the air cavity is the smallest,and the seed is the most full.The embryo vigor and germination rate are the highest of xenogamy,and the capsules develop faster.(2)The embryonic development process of C.appendiculata was studied with buds and ovaries at different stages.The results showed that the pollen grains of C.appendiculata were always covered by callose and aggregated into lumps during the whole process of the anther development.The anther wall tapetal layer is deformed tapetal layer and is in the mononuclear stage all the time.There are 4 pollen sacs in anther,the tetrad of microspore isdominated by tetrahedral shape,also has left and right symmetry shape,mature pollen grains are two-cell pollen grains.The embryo sac was not developed when anther was mature,but stimulated after pollination.Megaspore mother cells undergo meiosis to form a linear tetrad.The three megaspores near the chalazal end degenerate and disappear,and only the micropyle end develops into a functional megaspore.The inner integument is composed of two layers of cells.During the embryonic development process,the inner integument cells gradually form a tight film close to the germ embryo.Mononuclear embryo sac develops into mature embryo sac after mitosis for 3 times.The mature embryo sac is composed of 8 cells.The central cells do not fuse before pollination.(3)the fertilization method of C.appendiculata is porogamy.The endosperm nucleus disappears and degenerates without division.For the first time,the zygote divides into two cell proembryo,a large basal cell and a small apical cell.Subsequently,the two-cell proembryo continued to divide to form a spherical multicellular proembryo.The cells at the top of the proembryo were quadrilateral,small in size and neatly arranged.The cells in the middle of the proembryo were large in size.The basal part is the suspensor cell,which is large.At harvest time,the seed only consist of single extracellular seed coat,tight membrane inner seed coat and undifferentiated spherical proembryo.The globular proembryo of C.appendiculata undergoes pear-shaped proembryo during germination.In the process of germination,the structure of the embryo was developed gradually.According to the structural changes during germination,germination can be divided into three stages: water absorption and expansion stage,protocorm formation stage and germination stage.In the first stage,the spherical proembryo breaks through the seed coat from one side,and the proembryo is white and transparent.When the proembryo develops to the pear-shaped embryo,the embryo shows polarity,At one end the surface cells divide to form meristem,at the other end the cells become larger and the cells differentiate into parenchyma cells.In the second stage,the embryo was completely separated from the seed coat.In the initial stage,the surface cells bulges to form a large number of white and transparent "pseudo-roots".The "pseudo-roots" gradually began to disappear when the procorm changed from white and transparent to light green.The formation of procorm germ and hypocotyl primordia was observed by sectioning.In the third stage,the germ primordiumfirst differentiates into young leaves,and then the radicle primordium differentiates and develops into roots,and then between the base of the leaves and the roots bulges into pseudobulbs.