玉米原生质体超低温保存后芽和根的分化

植物细胞的超低温保存,已逐步发展成为一个有效的种质保存方法。近年来,随着原生质体再生植株种类的不断增多,禾谷类的主要农作物比如水稻、玉米、小麦等     

PHYTOREMEDIATION POTENTIAL OF MAIZE (ZEA MAYS L.) IN CO-CONTAMINATED SOILS WITH PENTACHLOROPHENOL AND CADMIUM

The ubiquitous coexistence of heavy metals and organic contaminants was increased in the polluted soil and phytoremediation as a remedial technology and management option is recommended to solve the problems of co-contamination. Growth of Zea mays L and pollutant removal ability may be influenced by interactions among mixed pollutants. Pot–culture experiments were conduced to investigate the single and interactive effect of cadmium (Cd) and pentachlorophenol (PCP) on growth of Zea mays L, PCP, and Cd removal from soil. Growth response of Zea mays L is considerably influenced by interaction of Cd and PCP, significantly declining with either Cd or PCP additions. The dissipation of PCP in soils was notably affected by interactions of Cd, PCP, and plant presence or absence. At the Pentachlorophenol in both planted and non-planted soil was greatly decreased at the end of the 10-week culture, accounting for 16–20% of initial extractable concentrations in non-planted soil and 9–14% in planted soil. With the increment of Cd level, residual pentachlorophenol in the planted soil tended to increase. The pentachlorophenol residual in the presence of high concentration of Cd was even higher in the planted soil than that in the non-planted soil.     

密度对玉米群体冠层内小气候的影响

 系统研究了两个玉米(Zea mays L.)品种不同密度群体冠层内光合有效辐射、CO2浓度、温度、风速、相对湿度等小气候因子垂直分布及其变化。指出,密度能显著影响小气候因子在群体中的分布,并最终反映在群体的有效贮积能量上。通过合理密植能调节群体结构、充分利用小气候资源,获得较高有效贮积能量。     

THE EFFECTS OF GENOTYPE AND PLOIDY LEVEL ON POLLEN SURFACE SCULPTURING IN MAIZE (ZEA MAYS L.)

Pollen exine sculpturing is a consistent feature of seed plant taxa, yet no mechanism for control of sculpturing pattern has been found. On grass pollen, exine sculpturing takes the form of closely packed spinules. Exine spinules on pollen grains from six maize populations representing all combinations of three genetic backgrounds (single cross hybrids W22 W23, N6 W23, R75 W23) and two ploidy levels (2x, 4x) were examined by scanning electron microscopy. Doubling ploidy levels from 2x to 4x increased pollen diameter (minor axis) with the magnitude of increase related to genetic background. For spinule density, only the effect of genetic background was statistically significant. Spinule density was altered by the genotype of the plant on which the pollen was produced but not by the ploidy level, including genome number and difference in surface area and cytoplasmic volume resulting from chromosome doubling.     

玉米原生质体的植株再生

以玉米花粉诱导产生的胚性愈伤组织,在 N6基本培养基附加激动素2 mg/l,6-苄基氨基嘌呤1mg/l,2,4-D 0.3 mg/l,水解酪蛋白500 mg*l 及谷酰胺250 mg/l 的培养基上进行转代培养。用转代培养一年半后的胚性愈伤组织分离原生质体,原生质体培养在附加激动素0.2 mg/l,6-苄基氨基嘌呤0.1 mg/l,2,4-D 0.5 mg/1,水解酪蛋白200 mg/l,谷酰胺100 mg/l及椰乳296的原生质体培养基 Z_2中。培养4—6天后,原生质体的再生细胞进行第一次分裂;培养3星期后发育成肉眼可见的小愈伤组织。此后,需添加降低糖浓度的同样原生质体培养基 Z_2共两次。待再生愈伤组织长到直径2—4 mm 大小时,把它们先后转经第一及第二(即Z_3及 Z_4)分化培养基上诱导器官分化。最后在 Z_4分化培养基上同时有胚状体的发生及植株的分化。     

PROLIFERATION AND PLANT REGENERATION FROM THE NODAL REGION OF ZEA MAYS L. (MAIZE,GRAMINEAE) EMBRYOS

Immature embryos of Zea mays L. (maize), cultured on Murashige and Skoog's medium containing 2,4-dichlorophenoxyacetic acid (2,4-D, 0.25–1.0 mg/l) and sucrose (3, 6 and 12%), produced a narrow ridge of tissue in the nodal region of the embryo axis, opposite the scutellum. Only those embryos which were placed with the scutellum in contact with medium showed such a response. The ridge of tissue further proliferated and formed a compact and opaque callus that appeared similar to the scutellar callus. Morphogenesis took place on media containing low concentrations of both 2,4-D and sucrose. Plant regeneration was achieved and is interpreted to take place by the precocious germination of somatic embryos. It is suggested that the ridge of tissue formed at the node may represent an evolutionarily extinct epiblast of the maize embryo and may be cotyledonary in nature.     

THE INFLUENCE OF INDIVIDUAL EMBRYONIC TISSUES ON THE MORPHOLOGY AND DEVELOPMENT OF ZEA MAYS (POACEAE) GERMLINGS

Mature embryos of Zea mays L. (inbred A188) were used in this study, which was undertaken to investigate three questions: 1) do all embryonic tissues of Zea, viz., coleoptile, scutellum, epicotyl, mesocotyl, hypocotyl, and coleorhiza, influence germling morphology and growth; 2) if a given tissue does exert an influence, what is it, and 3) what effect does removal of one tissue have on that tissue and on the tissues remaining? Experimental results revealed growth of isolated epicotyls was greater than that of epicotyls still attached to the scutellum, but it was less than that of whole embryo controls. Isolated hypocotyls grew less than any other tissue except scutella, which seemed to have no growth response. Hypocotyls still attached to the scutellum had the greatest growth response of all tissues. Intact embryo axes had a response intermediate to whole embryo controls and isolated epicotyls. Growth of the epicotyl is influenced most strongly by the hypocotyl, and growth of the hypocotyl, by the scutellum. The mesocotyl does not appear to have a regulatory influence on other tissues. It is proposed that the scutellum synthesizes or otherwise provides a growth factor (nutrients, growth regulator, or combination thereof) which is the initial stimulus for hypocotyl and root growth during germination, and that the epicotyl has a regulating influence on this factor in germlings and young seedlings.     

ULTRASTRUCTURE OF THE LAMELLAE AND GRANA IN THE CHLOROPLASTS OF ZEA MAYS L

The fine structure of the chloroplasts of maize (Zea mays L.) has been investigated by electron microscopic examination of ultrathin sections of leaves fixed in buffered osmium tetroxide solutions. Both the parenchyma sheath and mesophyll chloroplasts contain a system of densely staining lamellae about 125 A thick immersed in a finely granular matrix material (the stroma), and are bounded by a thin limiting membrane which often appears as a double structure. In the parenchyma sheath chloroplasts, the lamellae usually extend the full width of the disc-shaped plastids, and grana are absent. The mesophyll chloroplasts, however, contain numerous grana of a fairly regular cylindrical form. These consist of highly ordered stacks of dense lamellae, the interlamellar spacing being ca. 125 A. The grana are interlinked by a system of lamellae (intergrana lamellae) which are on the average about one-half as numerous as the lamellae within the grana. In general, this appears to be due to a bifurcation of the lamellae at the periphery of the granum, but more complex interrelationships have been observed. The lamellae of the parenchyma sheath chloroplasts and those of both the grana and intergrana regions of the mesophyll chloroplasts exhibit a compound structure when oriented normally to the plane of the section. A central exceptionally dense line (ca. 35 A thick) designated the P zone is interposed between two less dense layers (the L zones, ca. 45 A thick), the outer borders of which are defined by thin dense lines (the C zones). Within the grana, the C zones, by virtue of their close apposition, give rise to thin dense intermediate lines (I zones) situated midway between adjacent P zones. A model of the lamellar structure is proposed in which mixed lipide layers (L zones) are linked to a protein layer (P zone) by non-polar interaction. Chlorophyll is distributed over the entire lamellar surface and held in the structure by van der Waals interaction of the phytol "tail" with the hydrocarbon moieties of the mixed lipide layers. The evidence in favour of the model is briefly discussed.     

钙提高玉米种子活力的作用研究

本文以玉米种子为材料,研究了钙对种子活力的影响．在０—４０ｍｍｏｌ／ＬＣａ（２＋）的浓度范围,低浓度的Ｃａ（２＋）提高种子的发芽率和活力,最适浓度为１０ｍｍｏｌ／Ｌ,超过此浓度Ｃａ（２＋）的促进作用减弱．Ｃａ（２＋）提高种子发芽率和活力的原因可能是Ｃａ（２＋）促进胚和胚乳中α－和β－淀粉酶的活性,加速胚乳中贮藏物质如淀粉和可溶性蛋白的动员．在种子萌发过程中,ＥＧＴＡ和ＥＤＴＡ能降低种子活力,２．５和１０ｍｍｏｌ／ＬＣａ（２＋）能部分解除ＥＧＴＡ和ＥＤＴＡ的抑制作用．