Reproductive Biology Of Amygalus Monogolica

Amygalus monogolica Maxim.which belongs to Amygalus in Rosaceace is a specific and rare species in Chinese desert and arid area. It is mainly distributed in Neimenggu,Gansu and Ningxia province. Several studies were investigated on A.monogolica which spread in Yinchuan city and east foot of Helan Mountain to explore the factors which caused its low fruit setting rate,we also compare the differences between A.Monogolica and two other Almonds:Amygdalus tangutica (batal.) Korsh and Amygdalus Pedunculata Pall. Their flowering dynamics were recorded,the activities of pollen and stigma were tested, the length of stamen and pistil and the quantity of pollen and ovule were measured. Artificial pollination and microscopic observation were also carried to anaylse the role of breeding system in A. monogolica. And for inner research, the growth of its male gametophyte; female gametophytes and embryo were observed by paraffin section. The results are follows:1.The stylar polymorphic phenomenon in A.monogolicaAccording the length of stylars, flowers could be divided into three types:long-style(LS) flower, middle-style(MS) flower and short-style(SS) flower. The length of LS is about 8-10mm, longer than stamen. The length of SS is about 2-3mm, lower than all stamen significantly. And the length of MS is about 5mm, just close to the average length of stamen. Howerver, they have no differences in the length of stamen nor the quantity and quality of pollen. Some LS were bending at some degrees. Three different types flowers coexist in a same individual, while different individuals own different distribution proportion. In the same plants, with the process of anethesis, the average length, the longest length and the lowest length were increased. Short-style flowers are sterile, long-style flowers and middle-style flowers are fertile.2.The formation of male gametophyte and female gametophyteThe formation of microspore started from September, After a few sporogenous cell mitosis microsporecyte were born, microsporecyte then generated tetrad which turned into four mononuclear pollens. The mononuclear pollens will be dormancy till March in next year,then devided to bisnuclear pollens till bloom. In this case, the formation of mocrospore and male gametophyte have cross two growth season.The megaspore formatted in March, and matured before bloom. Matured embryo include two synergrids, one egg cell, one central cell and three antipodal cells.3.The growth of embryo in A.monogolicaDouble fertilization is complete, fertilized polar nuclear begin to split into nuclear endosperm and degenerated in a certain period. Fertilized polar nuclei began to break up shortly after the zygote began to split. Zygote began to split after endosperm.Its first devision forming the upper and lower cells. Then the upper cells through two cells, four cells, eight cells levels and at last formatted the globular pro-embryo. And then through the heart-shaped embryo, torpedo-shaped embryo, and finally the hypertrophy, including two cotyledons, plumule, hypocotyl and radicle of mature embryos were formatted.4. Differences between A.tangutica, A.Pedunculata and A.monogo licaA.Pedunculata bloom 20 days later than A.monogolica while A.tangutica bloom 10 days before A.monogolica. Their size of spores,the occurrence and development process of male and female gametophyte were similar to A.monogolica,but the fruit setting rating is much higher.A.tangutica appear no stylar polymorphism phenomenon. But there are very few pistil degraded, however, sterile pistil were no significant differences in shape. Although both there are several differences in their appearance, but the occurrence and developmentof gametes and embryo is similar. There are a large number of nucellar cells in relatively small parcels of the embryo sac structure; and in pairs of ovule,only one could be able to form a seed while the other one occurred degradation. Their pollen grains are nearly spindle-shaped, and male gametes grows in winter while flowering in next year. In addition, the three are all self-incompatibility plants which need insect pollination...