Spatial-Temporal Characteristics of Primary and Secondary Educational Resources for Relocated Children of Migrant Workers: The Case of Liaoning Province

Appropriate spatial distribution of primary and secondary schools for relocated children of migrant workers (RCMW) is extremely valuable to ensure the fair education of special groups and improve the quality of their education. This study used concentration analysis, kernel density estimation (KDE), and coefficient of variation (CV) to measure the spatial agglomeration of these children and their primary and secondary schools in the districts and counties of Liaoning Province from 2008 to 2017 based on government surveys. The results showed that the number of RCMW children in primary and secondary schools increased during the research period and the growth rate of children in primary schools was higher than that of children in junior high schools. The number of primary and secondary schools has changed very little, while the number of secondary schools has dropped sharply. The spatial distribution of RCMW and that of their primary and secondary schools were characterized by a “dual-core” distribution and a three-level (county, city, and provincial capital) gradient aggregation. In addition, kernel density evolved from a balanced distribution to polar nucleus-shaped, clustered, and discretized distributions, respectively. Specifically, the “large” and “super-large” schools were mainly concentrated in cities, showing a clustered pattern. “Medium-sized” and “small” schools were mainly distributed in counties, presenting a discretized pattern. In addition, when the CV of the number of RCMW increased, the imbalanced distribution of schools became more significant. Furthermore, the spatial differentiation of primary and secondary schools for RCMW appeared to be affected by economic development, population size, and related policies in the region.

Spatial and temporal pattern evolution and influencing factors of energy–environmental efficiency: A case study of Yangtze River urban agglomeration in China

Improving energy–environmental efficiency is prerequisite for sustainable development. In order to explore ways to improve energy–environmental efficiency, this paper uses the undesired output slack-based model to measure the energy–environmental efficiency of the Yangtze River urban agglomeration based on the input and output index data from 2008 to 2017, and its spatial and temporal pattern evolution is analyzed by using kernel density estimation, Gini coefficient, and coefficient of variation. Moreover, the Tobit regression model is used to analyze the influencing factors of the energy–environmental efficiency of the Yangtze River urban agglomeration. The results indicate that the energy–environmental efficiency of each city is increased continuously, and the regional differences are gradually narrowed. The spatial pattern is changed from polar nucleus type to valley type, and finally the distribution characteristics of “overall high” are formed. Overall, the energy–environmental efficiency presents a spatial layout of “high in the east and low in the west.” The regression results show that the level of economic development and energy–environmental efficiency are “U-type” associated characteristics, and government regulation and population density have significant positive effects on it. Industrial structure and technological progress have negative effects on it, and the effect of opening degree is not significant.

Pollen Tube Growth and Double Fertilization in Camellia oleifera

Camellia oleifera is an important plant species that produces edible oils. Understanding the double fertilization of this plant is critical for studies concerning crossbreeding, self-incompatibility, and the biological mechanisms underlying hybridization. We aimed to characterize pollen tube growth and double fertilization in C. oleifera. The female and male parent cultivars (Huashuo and Xianglin XLC15, respectively) were used for artificial pollination. Growth of the pollen tube in the style, ovary, and ovule from pollination to fertilization and the cytological characteristics of female and male gamete fusion during double fertilization were observed using fluorescence and scanning electron microscopy (SEM). Numerous pollen grains germinated 2 to 4 hours after pollination. The pollen tubes entered the interspaces between the papillar cells, grew along the stylar canal, and aggregated at the one-third site of the style. They grew in the gradually narrowing stylar canal, entering the locule. The tubes turned 90° and entered the embryo sac through the micropyle; subsequently, they entered a degenerated synergid, where the spermatids were released. One sperm nucleus fused with the polar nucleus, forming the primary endosperm nucleus, whereas the other sperm fused with the egg, forming the zygote. The polar nucleus was fertilized earlier than the egg. Double fertilization of C. oleifera is characterized as pre-mitotic gametogony. The current results lay a theoretical foundation for studies concerning the crossbreeding and embryology of C. oleifera and provide fundamental data concerning the reproductive biology of the genus Camellia.

The ultrastructure of the mature embryo sac in the natural tetraploid of red clover (Trifolium pratense L.): that has a very low rate of seed formation

In this study, ultrastructural organization of cells in the mature embryo sac of natural tetraploid <em>Trifolium pratense</em> L. was investigated. The mature embryo sac of this plant contains an egg cell with two synergids at the micropylar end, and a central cell with two polar nuclei. The ultrastructure of these cells agrees with what is known for most angiosperms studied with the electron microscope. The egg cell is a large and highly vacuolate cell, partially surrounded by a wall. Much of the cytoplasm is located around the nucleus at the chalazal end and there are few numbers of channel-shaped endoplasmic reticulum, mitochondria, plastids and numerous ribosomes distributed throughout the cytoplasm. Unlike the egg cell, much of the cytoplasm in synergid cells is located at micropylar part of the cell and the synergid cytoplasm contains especially, large numbers of rough endoplasmic reticulum, free ribosomes, mitochondria and plastids. The central cell of <em>T. pratense</em> L. contains two large polar nuclei which lie close to the egg apparatus. Each polar nucleus has a single, large, dense nucleolus that contains several nucleolar vacuoles. Much of the central cell cytoplasm consisting of granular and agranular endoplasmic reticulum, mitochondria, plastids, ribosomes, dictyosomes and lipid bodies are placed around polar nuclei.

Cytologie et histologie de la reproduction chez le Nymphaea heudelotii

The ontogenesis of reproductive cells has been cytologically analysed in Nymphaea heudelotii Planch., family Nymphaea-ceae, subclass Magnoliidae. Our observations of embryo sac development on sections differ from those made by Cook in 1906. Embryo sacs derive from a single functional megaspore and are four nucleate. After fertilization, the polar nucleus divides and successively generates two storage tissues that are located in two separate chambers. Nucellar tissue, which is filling up with starch inclusions, then insures a storage function. This species possesses 14 bivalents at meiosis and 14 somatic chromosomes at the first mitosis of the pollen grain. A reorganization of amyliferous organelle aggregates has also been observed in microsporocytes. Key words: reproduction, embryogenesis, microsporogenesis, megasporogenesis, Nymphaea.

The development of the central cell of Brassica campestris prior to fertilization

The development of the central cell of Brassica campestris cv. Candle (canola-rapeseed) was examined using techniques of light and electron microscopy and cytochemistry. The mature central cell is devoid of the large central vacuole characteristic of the early cellular stage of megagametophyte development. Prior to anthesis, cell wall projections, of the transfer cell type, develop on the lateral wall of the central cell. These central cell wall projections extend from the midregion of the megagametophyte to the egg apparatus and are immediately adjacent to the starch-containing region of the inner and outer integuments. The cell wall projections are periodic acid – thiocarbohydrazide – silver proteinate positive as are the contents of dictyosome vesicles that appear to contribute to their formation. Mitochondria are associated with the wall projections as is a network of central cell endoplasmic reticulum that extends from the wall projections to the egg apparatus. Microtubules are associated with the migrating chalazal polar nucleus. The two polar nuclei partially fuse prior to double fertilization, united by nuclear bridges and endoplasmic reticulum interconnections. Proplastids are a characteristic feature of the immature cellular megagametophyte. By anthesis, the proplastids of the mature central cell develop into chloroplasts with stacked thylakoids and starch deposits. Microbodies are frequently found associated with lipid bodies, and polysomes with the endoplasmic reticulum of the mature central cell. Key words: Brassica, central cell, megagametophyte, ovule, transfer cell.

Detection of the time of occurrence of nondisjunction induced by the r-X1 deficiency in Zea mays L.

The r-X1 deficiency in maize produces high frequencies of aneuploid progeny by inducing nondisjunction during embryo sac development. The purpose of this investigation was to determine the embryo sac division at which the nondisjunctive event takes place. Monosomic-6 individuals were generated by crossing r-X1 containing plants by those carrying the y-pastel-8549 allele of the Y locus on chromosome 6. A strict dosage relationship exists between the number of dominant alleles of the Y locus and the level of β-carotene in the endosperm. We found that the level of β-carotene in the endosperm of kernels containing monosomic-6 embryos was comparable with that found in endosperms with one Y allele. This indicated that they contained only one maternally contributed chromosome 6. Only nondisjunction at the second postmeiotic division could have produced such an endosperm; thus, the nondisjunctive event occurs at this division. Another endosperm type expected from nondisjunction at this same division, with three dominant Y alleles, was not found. The absence of this endosperm type suggests that the egg nucleus and the polar nucleus originating at the micropylar pole are sister nuclei that arose from the same cell at the third embryo sac mitotic division. Key words: aneuploidy, embryo sac, nondisjunction, r-X1 deficiency, Zea.

Megagametophyte development in Hordeum vulgare. 2. Later stages of wall development and morphological aspects of megagametophyte cell differentiation

The micropylar quartet of nuclei in the barley megagametophyte is first partitioned by a vertical wall between the synergid nuclei and by an initially horizontal wall between the micropylar polar and egg nuclei. The latter wall continues to grow in an expanding horizontal plane forming much of the upper wall of all three egg apparatus cells and eventually fusing with the megagametophyte wall peripherally. A branch of the egg – polar nucleus wall grows in a micropylar direction and becomes attached to the megagametophyte wall. After partitioning, the egg apparatus is composed of three flat cells having a ceiling wall and two upright supporting walls, which are fused centrally. The micropylar polar nucleus lies just chalazal to the ceiling wall. Expansion of the egg apparatus results in rounding of all three cells followed by lengthening and thinning of their walls in contact with the central cell. Probable membrane contacts may facilitate sperm transmission after pollination. Partitioning of the chalazal quartet of nuclei exhibits many similarities to that of the egg apparatus but with a different cellular arrangement. Transfer cell wall ingrowths appear in cells at both poles of the megagametophyte. Such ingrowths appear in the two synergid cells, representing the filiform apparatus. They also develop in two of the original three antipodal cells where these cells are in contact with the megagametophyte wall. Either the micropylar or chalazal polar nucleus migrates to a position close to the other polar nucleus. Partial fusion of polar nuclei occurs later.

Ontogenèse des sacs embryonnaires non réduits chez Eragrostis curvula

The apomictic reproductive mode by diplospory is cytologically analysed in Eragrostis curvula (Schrad.) Nees, a tetraploid forage grass. The genesis of unreduced embryo sacs is followed; two kinds of sacs are then distinguished: (i) a monopolar one with a typical oogonial complex and a polar nucleus at the micropylar end; (ii) a bipolar one with an egg cell and two polar nuclei at the micropylar end, and some antipodial cells at the chalazal end. Monopolar sacs are 3 times more frequent than bipolar ones. Traces of sexuality are noted in E. curvula but with a low frequency. A chronology of female development is established according to stages of male development. This should make possible an early distinction and allow a useful comparison between diplospory and sexuality within the genus Eragrostis.