红葱种群地上和地下构件的密度制约调节

虽然个体大小和密度的关系是植物生态学研究的中心问题, 但是大多数基础研究只观测植株地上部分的生物量, 即地上部分大小-密度关系, 而对于地下构件大小-密度关系的研究十分薄弱。因为植物个体的生长是构件变化的过程, 所以个体大小和密度的关系不仅表现为种群水平和个体水平, 也表现为构件水平。该文研究了5个密度(36、49、64、121和225株·m^-2)的红葱(Allium cepa var. proliferum)种群地下构件密度制约调节规律及其与地上构件密度制约调节规律的关系, 地下部分和全株(包括地上部分和地下部分)的密度制约调节规律, 及二者与地上部分密度制约调节规律的关系。结果表明: (1)不同密度环境下, 植物的表型可以通过各器官形态的可塑性反应发生调整; 植株地下构件和地上构件的各个特征(株高、叶片长、叶片数、鳞茎直径、分蘖重)均与密度呈显著的线性相关关系; (2)平均根、鳞茎、叶片和鞘生物量均与密度呈显著的幂函数负相关关系, 但异速指数不同: 鳞茎(-1.14)<叶片(-1.03)<根(-0.78)<鞘(-0.49), 表明地下构件的大小和地上构件的大小随密度的变化不一致; (3)平均地下、地上和个体生物量均与种群密度呈显著的幂函数负相关关系, 但异速指数不同, 分别为: -1.13、-0.95和-0.98, 表明地上部分大小和全株大小随种群密度的变化基本一致, 但与地下部分大小的变化不一致。总之, 密度制约对植株地下构件的调节作用大于地上构件, 对地下部分的调节作用大于地上部分, 红葱种群对地下资源的竞争占主导地位。     

Improved Growth of Tissue Cultures of the Onion, Allium cepa

A forty-fold increase in tissue fresh weight has been achieved for Allium cepa stem tissue callus grown on a modified B5 medium with increased ammonium, phosphate and nitrogen levels; and decreased level of 2,4-dichlorophenoxyacetic acid. Growth was examined on several standard media, using fresh weight, dry weight and cell number as parameters over an 8-week growth period. Further, tissue grown upon this medium is more friable than on other media. The value of such friable callus for suspension culture initiation and for single cell cloning experiments is discussed.     

Clonal Variation in Growth and Flavour Production in Tissue Cultures of Allium cepa L.

Callus cultures of onion were initiated from seedling root tissueof three varieties, Rijnsburger, White Lisbon and Red Italian.Twenty separate clones of each variety were sub-cultured fornine passages and estimates made of growth, friability, sliminessand pigmentation at each sub-culture; measurement of alliinaseactivity and precursor level was made at the ninth sub-culture.A number of clones showing a uniformity in one or more charactersappeared but clonal characteristics could not be correlatedwith alliinase activity or flavour precursor levels. The alliinaseactivity was comparable to the normal plant but the precursorlevel was 2–10 per cent of that in the plant. The workshows that despite the large number of separate cultures establishedand the development of stable clonal lines, it was not possibleto select out a clone able to produce a high level of the onionflavour compounds.     

珍稀濒危植物毛柄小勾儿茶的离体培养

以珍稀濒危植物毛柄小勾儿茶（Berchemiella wilsonii（Schneid．）Nakai var．pubipetiolata H．Qian）嫩梢为外植体进行组织培养实验,结果表明：以1／2 MS＋6-BA0．5mg／L＋NAA 0．05mg／L为芽诱导培养基、MS＋6-BA0．5mg／L＋NAA 0．05mg／L为增殖培养基,可以得到大量的毛柄小勾儿茶试管苗。     

Callus, Organogenesis and Plantlet Formation in Tissue Cultures of Clitoria ternatea

Decoated seeds of Clitoria ternatea L. germinated on Murashigeand Skoog (Physiologia Plantarum 1962, 15, 473–97) basalmedium (BM) and differentiated callus and bipolar embryoids(two-step method) in low frequency. Calluses developed on lateralroots [BM+KN(0.1 mg 1^–1)], on roots and hypocotyls [BM+KN(0.5mg 1^–1)], and on roots [BM+KN+IAA (0.5 mg 1^–1 ofeach)]. On basal medium with KN (0.5 mg 1^–1) and withKN+IAA (0.5 mg1^–1 of each), multiple shoot buds and embryoids(one-step method) were differentiated directly on split hypocotylsand roots. In the former, shoot buds developed even on unsplithypocotyls. Rhizogenesis on isolated shoot buds occurred efficientlyin BM+indole butyric acid (IBA 0.1 mg 1^–1) and BM+IAA(0.1 mg 1^–1 and 0.5 mg 1^–1). Profuse direct embryoidsand shoot buds developing on root systems are interesting morphogeneticphenomena rarely reported. Clitoria ternatea L., callus, embryoids, multiple shoot buds, regeneration     

BAC FISH analysis in Allium cepa.

Onion (Allium cepa L.; 1C=15,000 Mb) is an agriculturally important plant. The genome of onion has been extensively studied at the conventional cytogenetic level, but molecular analyses have lagged behind due to its large genome size. To overcome this bottleneck, a partial bacterial artificial chromosome (BAC) library of onion was constructed. The average insert size of the BAC library was about 100 kb. A total of 48,000 clones, corresponding to 0.32 genome equivalent, were obtained. Fluorescent in situ hybridization (FISH) screening resulted in identification of BAC clones localized on centromeric, telomeric, or several limited interstitial chromosomal regions, although most of the clones hybridized with entire chromosomes. The partial BAC library proved to be a useful resource for molecular cytogenetic studies of onion, and should be useful for further mapping and sequencing studies of important genes of this plant. BAC FISH screening is a powerful method for identification of molecular cytogenetic markers in large-genome plants.     

A Comparison of Pectinases from Ditylenchus dipsaci and Allium cepa Callus Tissue

Ground and whole Ditylenchus dipsaci maintained on onion callus contain no culturable micro-organisms when tested with five check media. Healthy onion callus does not produce pectolytic enzymes. Pectolytic enzymes are present in infected callus. These enzymes are, however, associated with resident nematodes and not host tissues. These results suggest that D. dipsaci is the actual source of the endo-polygalacturonase and endo-pectinmethyltrans-eliminase extracted from them.     

A Field and Storage Rot of Onion (Allium cepa L. var. cepa) Caused by Pseudomonas cepacia in Lowland Papua New Guinea

A bacterium consistently isolated from rotting onions in the field and in storage was shown by biochemical and pathogenicity tests to be Pseudomonas cepacia. In experiments to determine the mode of entry of the pathogen only injured bulbs developed a soft rot after a 10 min soak in a suspension of P. cepacia (approx. 10⁸ cfu/ml).     

Interspecific hybrid between Allium cepa and Allium sativum

Summary Interspecific hybrids between Allium cepa and Allium sativum were obtained using the fertile clone A. sativum as the male parent. The nascent embryos which formed shortly in interspecific hybridization between A. cepa and A. sativum were rescued by ovule culture at an early stage. The zygotes or proembryos developed in Murashige and Skoog medium containing 5.7×10^-8 M indole-3-butyric acid (IBA). Once developed, the embryos were taken out of the ovule and cultured on embryo culture medium where they regenerated into whole plants. The hybridity of the plants obtained was examined by morphological observation, chromosome analysis, and ribosomal RNA gene analysis. The analyses proved that the plants were mature sexual hybrids between A. cepa and A. sativum. Each hybrid plant had keeled but fistulose leaves and formed a bulb resembling that of A. cepa. The hybrids produced not only S-propenyl-l-cysteine sulfoxide, which is the major flavor precursor in A. cepa, but also S-allyl-l-cysteine sulfoxide (alliin), which is characteristic of A. sativum.     

Chemical Regulation of Callus Growth, Organogenesis, Plant Regeneration, and Somatic Embryogenesis in Antirrhinum majus Tissue and Cell Cultures

Excised stem explants of Antirrhinum majus L. var. ‘Kymosyblanc’ were grown in a denned medium to investigate factorsinfluencing bud and root development, callus induction, andsomatic embryogenesis. Auxins such as indoleacetic acid (IAA)and naphthaleneacetie acid (NAA) caused limited callus developmentand abundant root formation, whereas 2,4-dichlorophenoxyaceticacid (2,4-D) promoted soft friable callus with embryos and occasionaldevelopment of thick abnormal roots. 2-Naphthoxyacetic acid(NOA) and coconut milk (CM) used together induced friable greencallus growth and differentiation of small globular embryoswhich eventually developed into plantlets after transfer toauxin-free agar mineral medium containing sucrose. Cytokininssuch as benzyladenine (BA), zeatin, and kinetin induced compactgreen callus but in the absence of auxin failed to promote organogenesis.The interaction of IAA and kinetin resulted in the regenerationof the whole plant from stem explants. When NAA was used withkinetin, shoot development was totally inhibited and abundantroots were formed. Thus, the alternative morphogenetic eventsprobably reflect the biochemical subtleties occurring withinthe callus as a result of differences of actual endogenous levelsof growth substances in the tissues studied. These experimentshave been performed and interpreted on a histological basis.     

Synaptonemal complex spreading in Allium cepa and A. fistulosum

The general features and fine structure of homologous chromosome alignment and pairing have been investigated in two species of Allium (A. fistulosum and A. cepa), which have similar karyotypes but very different patterns of chiasma distribution. Although there is no support for the occurrence of a general pre-meiotic alignment of homologous chromosomes, both species show some alignment of homologues as an immediate prelude to synaptonemal complex (SC) formation. In both species pairing usually commences at sub-terminal sites and is succeeded by numerous separate intercalary initiations of pairing in interstitial and distal regions and then in proximal regions. The last parts to pair, in both species, are pericentromeric and telomeric regions. There is, therefore, no evident relationship between the sequence of pairing and chiasma distribution in these species. Regularly alternating convergences and divergences of aligned axial cores (ACs), termed multiple association sites, are frequently observed. It is proposed that these represent potential pairing initiation sites and from observations on their spatial distribution it is argued that they may be evenly distributed through most of the genome. Small spherical or ellipsoid nodules are found at association sites and between closely aligned ACs which persist in the SC segments present during zygotene, but most of them disappear abruptly at the end of zygotene. These are termed zygotene nodules (ZN) and it is proposed that they are involved in matching corresponding sites on homologous chromosomes as well as possibly having a recombinational role. Their composition, structure, mode of action and relationship to pachytene recombination nodules are at present unknown.     

Nucleolar Organizer ultrastructure in Allium cepa

The Nuoleolar Organizer Region (NOR) was studied in Allium cepa. The cells analyzed were: meristematic root tip cells, cells from the layers of the anther (exothecium, intermediate layer cells, endothecium and tapetum) and meiocytes from preleptotene to diptotene. Conventional electron microscope techniques and serial section were used in the study. Ultracytochemical tests, using preferential techniques for nucleic acids were also applied. The results show that: a) Although the NOR may have a very variable form in the different cells analyzed, in each case its fine structure is similar, being constituted of chromatin differentiated in high and low density zones. b) In each case, its cytochemical characteristics are similar; highly positively to EDTA (preferential stain for RNP) being observed in the low density zones. As scattered chromatin these would constitute the active regions of the NOR. c) In certain cases a clear relationship is seen between NOR volume and the size of the nucleolus. d) The chromatin associated to the NOR always appears as very dense zones. e) The NOR-Nucleolus relationships are established exclusively with the latter's fibrillar pars. f) The nucleolar segregation phenomenon takes place sometimes as a result of a NOR contraction and in other cases depends on the position of the NOR in relation to the nucleolus. g) In preleptotene, the NOR shows its characteristic morphology and is positive to EDTA, while from zygotene to diplotene the structure of the NOR presents no differences from the rest of the chromatin and only the lateral elements of the synaptonemal complex or its remnants are positive to EDTA. h) The synaptonemal complex runs through the NOR with no differentiation and on occasions its lateral elements show associations with the nucleolus.     

Synaptonemal-like complexes in Allium cepa Microspores

The paper describes the synaptonemal-like complexes found in the course of microsporogenesis in Allium cepa, during the young microspore stage. In longitudinal sections these structures are morphologically more or less like the synaptonemal complexes, which appear during the pachytene stage of meiosis, and consist of two regions resembling the lateral elements, separated from one another by a space measuring about 1000 Å, in which a central element is occasionally observed. When observed in transverse or oblique sections, their shape indicates that they are tubular structures with a central axis; they are generally observed as independent units inside the nucleus, sometimes associated with the chromatin masses.By using the uranyl-EDTA-lead staining method, which picks out the RNA the synaptonemal-like complexes, show up at the level of their lateral elements and a similar result can be achieved by using the alcoholic PTA technique, which is believed to be a selective staining method for histones. We suppose that the synaptonemal-like complexes consist, at least partially, of RNP material.     

Introgression of Allium fistulosum L. into Allium cepa L.: cytogenetic evidence

Summary A diploid Allium cepa plant was recovered from the backcross of an interspecific triploid (2 x A. cepa + 1 x A. fistulosum) to an A. cepa diploid which exhibited both A. cepa and A. fistulosum Adh-1 alleles. Cytogenetic analyses revealed a recombinant sub-telocentric chromosome. The ADH-1 locus is believed to be on the long arm of the sub-telocentric A. fistulosum chromosome 5. Meiosis of the triploid progenitor gives strong evidence that recombination occurred. A. fistulosum chromosome 8 has been substituted for A. cepa chromosome 1.Contribution of the College of Agricultural Sciences, Texas Tech University, Journal No. T-4-275     

Sister chromatid exchanges in Allium cepa

Differential staining of sister chromatids with Giemsa after BrdU incorporation into DNA was performed in Allium cepa L. chromosomes. A treatment solution containing 10^–7 M FdU, 10^–4 M BrdU and 10^–6 M Urd was found to ensure BrdU incorporation without affecting cell cycle duration. After several procedures before staining the slides with Giemsa had been tested, treatment with the fluorochrome compound 33258 Hoechst, exposure to UV light and heating at 55° C in 0.5×SSC, were found to be essential for good differentiation. The distribution of SCEs per chromosome agrees with the expected Poisson distribution. The mean value of SCEs per chromosome occurring when cells were exposed to the treatment solution for two consecutive rounds of replication (=5.5) was double the mean value observed when cells were exposed to the same treatment for only one round of replication (=2.8). SCEs were found to occur more frequently in those chromosome regions corresponding neither to C-bands nor to late replicating DNA-rich regions. Finally, the occurrence of SCEs involving less than the width of a chromatid is discussed.     

Nuclear matrix network in Allium cepa

The presence of a nuclear matrix network in animal cells has been claimed by many workers in the last decade. The purpose of our study was to see whether a similar structure could be identified in the cells of higher plants. Our work revealed the presence of a fibrillar nonchromatinic network in Allium cepa nuclei. This could be impregnated with AgNO₃ in intact cells as well as in isolated matrices at the light microscope level. It was seen to be associated with the chromosomes from early to late prophase and also in telophase. Ultrastructurally a fibrillar network comparable to that reported earlier from animal cells was observed. This network remained associated with metaphase and anaphase chromosomes and could be digested with pepsin. Biochemical estimation of the isolated matrix revealed it to be made up mainly of proteins (more than 90%), traces of DNA (less than 1%) and a small quantity of RNA. SDS PAGE showed three polypeptide bands in the molecular weight range of 55,000–63,000 daltons.