Studies On The Reproductive Biology Of Cerasus Japonica Var. Nakaii.

This study was on the subject of Cerasus japonica var. nakaii. that is one endemic dwarf fruit trees of northeast of our country. The investigation of the morphological differentiation in flower buds, flower organs and the development in megaspores, microspores, male and female gametophytes, embryo and endosperm, expounded its regularity in the reproductive growth phase by means of the technique of traditional paraffin section. To provide theoretical basis of systematics, breeding and production practice. The results were as follows:1. The flowers of Cerasus japonica var. nakaii. were a cluster of inflorescence, complete flower and typical rosaceae corolla. When the fruits were ripe in July flower bud differentiation of Cerasus japonica var. nakaii. began and high occurrence period was from July to September. Then the bud and trees came into dormancy in November, continued to develop next year. The stage of flower bud differentiation was divided into the beginning of differentiate, sepal primordium, corolla primordium, stamen primordium and carpel primordium stage. Buds on different locations of one branch and the several original buds in one bud had different. beginning periods of flower bud differentiation.2. Cerasus japonica var. nakaii. had many stamens. The mature anther had four microsporanges. The development of anther wall was basic type. It was the glandular tapetum. The microspore mother cells underwent meiosis, each producing tetrahedral tetrad of microspores. The cytokinesis division was simultaneous type. Meiosis steps were not necessarily simultaneous in one anther chamber. Mature pollen was 2-celled condition. The pollen had three germination aperture, rarely four. Profile was elliptical sphericity.3. Pistil composed by one carpel and one room. It was inferior ovary and marginal placentation. It had two anatropous ovules, one of which would degrade later. It had two developed layers of integuments and thick nucellus. Its micropyle canal was long and narrow. The mature embryo sac was long oval. Style was closed type and the stigma surface had obvious papillary structure. Stamen developed earlier than pistil.4. Zygote went into dormancy after postfertilization. Primary endosperm nucleus mitosis earlier than zygote to supply nutrition for embryo. The embryo occuring was asterad type. The mature embryo had embryo, radicle, cotyledon and hypocotyls. The development of endosperm was nuclear endosperm. The embryo developed three or four round cotyledon till fruits were mature at the beginning of August. Endosperm was completely absorbed until embryo was mature. There was little vestige around it. The seed was dicotyledonous and had no endosperm. The fruits were typical drupe.