芒果花药发育的细胞化学研究

芒果花药发育中,花药药壁体细胞中淀粉粒多糖和脂滴类物质一直很少,仅药室内壁细胞中有零星淀粉粒分布.到二胞花粉早期,花粉营养细胞中的大液泡消失,开始积累淀粉粒.芒果成熟花粉中储存营养物质主要是淀粉粒,而脂类物质一直很少.     

Interspecific somatic hybrids Solanum villosum (+) S. tuberosum, resistant to Phytophthora infestans

The interspecific somatic hybrids 4x S. villosum (+) 2x S. tuberosum clone DG 81-68 (VT hybrids) were obtained and characterized molecularly and cytogenetically.     

Biogenesis and function of the lipidic structures of pollen grains

 Pollen grains contain several lipidic structures, which play a key role in their development as male gametophytes. The elaborate extracellular pollen wall, the exine, is largely formed from acyl lipid and phenylpropanoid precursors, which together form the exceptionally stable biopolymer sporopollenin. An additional extracellular lipidic matrix, the pollen coat, which is particularly prominent in entomophilous plants, covers the interstices of the exine and has many important functions in pollen dispersal and pollen-stigma recognition. The sporopollenin and pollen coat precursors are both synthesised in the tapetum under the control of the sporophytic genome, but at different stages of development. Pollen grains also contain two major intracellular lipidic structures, namely storage oil bodies and an extensive membrane network. These intracellular lipids are synthesised in the vegetative cell of the pollen grain under the control of the gametophytic genome. Over the past few years there has been significant progress in elucidating the composition, biogenesis and function of these important pollen structures. The purpose of this review is to describe these recent advances within the historical context of research into pollen development. Received: 1 November 1997 / Revision accepted: 3 February 1998     

Ultrastructural aspects of storage lipid mobilization in the tapetum of Lilium hybrida var. enchantment

Stages in the formation and degradation of pollenkitt in the anther of Lilium have been investigated using the electron microscope. This material, which appears to be a complex of lipid and carotenoids, is formed during the autolysis of the tapetal cells by the fusion of lipidic inclusions with globules derived from plastids. Autolysis of the tapetal cells is progressive for it commences with the disintegration of many cytoplasmic components, followed by the breakdown of storage lipids. The plasma membrane maintains its integrity during these events apparently, by proliferation, aiding in the transfer of the products of hydrolysis into the loculus. During the course of lipid breakdown, a striking vacuolar system is formed in the tapetal cytoplasm, presumably containing the products of this hydrolysis. The source of membranes for this system is clearly the lipid globules themselves. The generation of the membrane apparently involves the participation of electronopaque material, possibly enzymic, contained within the lipid globules.     

Micropropagation of Albuca bracteata and A. nelsonii — Indigenous ornamentals with medicinal value

In this study, two species from the genus Albuca (Hyacinthaceae) with ornamental and medicinal properties were micropropagated. Adventitious bulblets of Albuca bracteata were cut into quarters and used as explants to examine the effect of temperature (10, 15, 20, 25, 30 or 35 °C), carbohydrates (glucose, fructose or sucrose at 0, 87.5, 175, 262.5 or 350 mM) and hormones (BA, mTR, NAA, IAA, GA₃, ABA or methyl jasmonate each at 0, 0.1, 1.0 or 5.0 mg/L) on the induction and growth of bulblets. Temperatures above 35 °C completely inhibited bulb formation, while induction at all other temperatures was high. Heaviest and largest bulbs formed at 20 °C. Low concentrations (87.5 mM) of all tested carbohydrates increased bulb induction compared to media without a carbohydrate source, while higher levels decreased bulblet induction. The cytokinins mTR and BA inhibited bulb induction, diameter and mass at moderate (1.0 mg/L) and high (5.0 mg/L) concentrations. GA₃, NAA and particularly IAA promoted bulblet induction, while ABA and methyl jasmonate had no significant effect on the induction or bulblet growth. Leaf material and young inflorescences of A. nelsonii were removed, decontaminated, and dissected into seven explant types: leaves, peduncles, pedicels, whole flowers, tepals, ovaries and anthers. These were placed on MS media without hormones, or containing 0.5 mg/L mTR, 0.5 mg/L NAA or 0.5 mg/L mTR + 0.5 mg/L NAA to establish which explant type and hormone combination promoted shoot formation. Some tepal and pedicel explants were capable of shoot production on media with both mTR and NAA, but peduncle explants produced the most shoots when mTR and NAA were both present in the culture medium. Flowers, leaves, ovaries and anthers were completely unresponsive, irrespective of medium composition. These techniques will aid the further horticultural development of these plants, and can be easily adjusted for other species within the genus to promote conservation.     

Micropropagation of Romulea minutiflora, Sisyrinchium laxum and Tritonia gladiolaris — Iridaceae with ornamental potential

Three species of the Iridaceae with ornamental potential were micropropagated with the intention of producing propagules more rapidly for possible commercialization. Shoot induction from in vitro germinated seedlings of Romulea minutiflora was obtained with 5.4 μM α-naphthaleneacetic acid (NAA) and 23.2 μM kinetin. Shoot explants formed corms best with 3.4 or 17 μM paclobutrazol, and one incidence of in vitro flowering was observed. Sisyrinchium laxum shoot explants produced more and healthier multiple shoots with meta-topolin (mT) than with 6-benzyladenine (BA). Rooting was best in control (no hormone) cultures, and addition of NAA and indole-3-acetic acid (IAA) inhibited root formation and growth of shoot explants, and formed short, stunted roots. Roots produced by indole-3-butyric acid (IBA) were morphologically most similar to those produced in control cultures. Liquid-shake culture of shoots did not lead to meristemoid formation, despite supplementation with various growth regulators (mT, GA₃ or paclobutrazol). Low temperature (10-20 °C) induced corm formation in Tritonia gladiolaris shoot cultures, while corm formation was completely inhibited above 20 °C. Increasing temperature from 10 °C to 15 °C and from 15 °C to 20 °C increased corm mass significantly. Paclobutrazol (3.4 μM), GA₃ (2.9 μM), NAA (5.4 μM ) or methyl jasmonate (4.5 μM ) could not induce corm formation at 25 °C, while at 15 °C, NAA and methyl jasmonate inhibited corm formation. These experiments successfully demonstrate the ease with which different genera of the Iridaceae can be multiplied in in vitro systems.     

杂种卡特兰花粉萌发和花粉贮藏性研究

以杂种卡特兰品种‘绿世界’(Rhyncholaeliocattleya Sung Ya Green‘Green World’)的新鲜花粉为试材,采用正交试验比较了蔗糖、H3BO3、CaCl2对花粉萌发的影响。结果表明,适宜的花粉培养基为:蔗糖100 gL-1+H3BO3 40 mgL-1+CaCl2 150 mgL-1。不同贮藏方法对杂种卡特兰花粉萌发率的影响较大,4℃低温湿润贮藏30 d后,花粉萌发率仅为3.5%,而4℃低温干燥贮藏、-20℃冷冻湿润和干燥贮藏720 d后,花粉仍然具有较高的活力,花粉萌发率均达32.5%以上,且对授粉结实率没有明显影响。杂种卡特兰的授粉最佳时期为开花后0-8 d,花粉块在整个花期均保持较高的活性。     

Comparative Observation on Leaf Anatomy and Pollen of Vernicia Lour. and Aleurites J. R. et G. Forst.

The folial anatomy and pollen of one species of Aleurites and two species of Vernicia were studied. The former genus is characterized by the presence of echinolophate sculpture of pollen and a single outer stomatal ledge, curved cuticular ridges of peristomatal rim as well as large nodular ornamentation on the surface of epidermis beneath which there is no hypodermis. The latter one is characterized by the verruca-murate sculpture of pollen and the cuticular striate ornamentation on leaf surface of epidermis beneath which there is one layer of hypodermis, although they both have paracytic stomata and the Crotonic type of pollen. The genus Vernicia has not been accepted for a long time, but these micromorphological characters show as additional evidence that recent separation of the two genera by Airy Shaw (1966)^[6] is reasonable. Both genera possess very similar xeromorphic feature designated here as orbicular lustrous spot.     

Physiological changes of a green alga (Micractinium sp.) involved in an early-stage of association with Tetrahymena thermophila during 5-year microcosm culture

Endosymbioses between phototrophic algae and heterotrophic organisms are an important symbiotic association in that this association connects photo- and heterotrophic metabolism, and therefore, affects energy/matter pathways and cycling in the ecosystem. However, little is known about the early processes of evolution of an endosymbiotic association between previously non-associated organisms. In previous studies, we analyzed an early process of the evolution of an endosymbiotic association between an alga and a ciliate by using a long-term culture of an experimental model ecosystem (CET microcosm) composed of a green alga (Micractinium sp.), a bacterium (Escherichia coli), and a ciliate (Tetrahymena thermophila). The results revealed that an algal type, isolated from 5-year cultures of the microcosm, prolonged the longevity of the ancestral and derived clones of T. thermophila in the absence of bacteria, suggesting that a cooperative algal phenotype that benefited the ciliate had evolved in the microcosm. Here, we investigated the physiological changes of the derived Micractinium clones that benefited Tetrahymena, focusing on the release of carbohydrates by and abundance of photopigments in the ancestral and 2 derived algal clones (SC10-2 and SC9-1) isolated from inside Tetrahymena cells. Analyses using HPLC revealed that the algal isolates released glycerol and sucrose at higher concentrations per cell and also contained higher levels of photopigments per cell at pH 7.2, in comparison with the ancestral strain. These phenotypic characters were considered responsible for the increased longevity of Tetrahymena cells, and thus supported the cooperator alga hypothesis.     

将安龙花转移至马蓝属(爵床科)的形态特征依据

比较了安龙花(Dyschoriste sinica H. S. Lo)的模式标本与距药花属(Dyschoriste Nees)和马蓝属(Strobilanthes Bl.)部分种类的花粉和花的特征后,支持将安龙花转移到马蓝属,组合为Strobilanthes sinica (H. S. Lo) Y. F. Deng。安龙花隶属于马蓝属黄猄草群,它与日本马蓝(Strobilanthes japonica (Thunb.) Miq.)近似,但区别在于它的匍匐习性,叶矩圆状椭圆形,近无柄,花单生叶腋。因此,距药花属(Dyschoriste Nees)在中国并没有分布。     

Characterization of a Plasmopara species on Ambrosia artemisiifolia, and notes on P. halstedii, based on morphology and multiple gene phylogenies

Common ragweed (Ambrosia artemisiifolia) is an invasive and highly allergenic plant species, on which two species, Plasmopara halstedii and Plasmopara angustiterminalis, have been recognized to cause downy mildew disease. In this study, morphological and molecular patterns of seven Plasmopara specimens collected from A. artemisiifolia in Canada, Hungary, and USA were compared with those of P. halstedii and P. angustiterminalis from Helianthus and Xanthium, respectively. Analyses of partial sequences of three genes, namely those for the large subunit (28S) of rDNA, cytochrome c oxidase subunit II (COX2), and NADH dehydrogenase subunit I (ND1) of mtDNA, were carried out to examine the phylogenetic relationships among these specimens using both Bayesian and maximum parsimony methods. All the phylogenetic analyses revealed that the downy mildew pathogens infecting A. artemisiifolia in Hungary and North America clearly represent a lineage distinct from other Plasmopara taxa investigated. The shape of sporangia and the width of trunks and branches also allowed the separation of the specimens parasitic to A. artemisiifolia from P. halstedii on Helianthus annuus and P. angustiterminalis on Xanthium strumarium. Surprisingly, the Hungarian and the Canadian specimens were more closely related to each other than to those from the USA based on COX2 and ND1 mtDNA data, although the D1/D2/D3 sequences of 28S rDNA were identical in all these Plasmopara specimens. The regional distribution of the mtDNA haplotypes seen in this study suggests a transatlantic migration has occurred and would be interesting to follow up with a more detailed sampling. To investigate the diversity within P. halstedii sensu lato, infecting different host plant species, specimens from six asteraceous genera, Ambrosia, Flaveria, Helianthus, Siegesbeckia, Solidago, and Xanthium, were also included in molecular analyses. These represented six distinct lineages according to the host plant genera. These findings might serve as a basis for a taxonomical reassessment of the P. halstedii complex and also for the delimitation of several well-defined species within this complex.     

Food intake and absorption are affected by dietary lipid level and lipid source in seabream (Sparus aurata L.) larvae

Marine larval nutrition studies have classically focused on essential fatty acid (EFA) requirements and very little is known regarding the effect of total lipid level or lipid source on food ingestion and absorption, which are important factors determining growth. In the present work two experiments analysed food intake and nutrient absorption in seabream larvae in response to two dietary lipid levels (17-18% and 25-28%). The first experiment tested Artemia enriched on two levels of a fish oil emulsion (higher and lower—HF and LF, respectively), while in the second experiment larvae were co-fed Artemia enriched on one of two levels of a soybean oil emulsion and a microdiet (MD) containing one of two levels of soybean oil as the main lipid source (higher and lower—HS and LS, respectively). Food intake and nutrient absorption were determined by performing radioactive trials using Artemia radiolabelled with [1-¹⁴C] oleic acid in the first experiment (at 26 and 33 days after hatching—DAH) and MD labelled with [1-¹⁴C] oleic acid or glycerol tri[1-¹⁴C] oleate (31 and 32 DAH) in the second experiment. The dietary treatments did not induce significant differences in larval dry weight in the first experiment, while food intake was significantly higher and nutrient absorption significantly lower in larvae fed the HF diet, compared to the LF treatment. In the second experiment, a significantly higher dry weight was achieved by larvae fed on the LS diet, which was also significantly more ingested and absorbed. The fish oil experiment supports the hypothesis that a higher food intake may cause a decrease in nutrient absorption efficiency, possibly through a faster gut transit, but in the soybean oil experiment total absorption appears to have simply reflected food intake. The results show that dietary lipid level significantly affects larval food intake and absorption efficiency but the effect was dependent on lipid source, suggesting that dietary fatty acid (FA) composition might be a more determinant factor than total lipid level. Food intake was apparently not regulated to meet a requirement for EFA. Lipid source or FA composition may regulate food intake through pre- or post-absorptive mechanisms, such as through effects on palatability, digestibility and stimulation of neuroendocrine pathways.     

In vitro and in vivo characterization of alkyl hydroperoxide reductase mutant strains of Helicobacter hepaticus

Mutant strains in the tsaA gene encoding alkyl hydroperoxide reductase were more sensitive to O₂ and to oxidizing agents (paraquat, cumene hydroperoxide and t-butylhydroperoxide) than the wild type, but were markedly more resistant to hydrogen peroxide. The mutant strains resistance phenotype could be attributed to a 4-fold and 3-fold increase in the catalase protein amount and activity, respectively compared to the parent strain. The wild type did not show an increase in catalase expression in response to sequential increases in O₂ exposure or to oxidative stress reagents, so an adaptive compensatory mutation has probably occurred in the mutants. In support of this, chromosomal complementation of tsaA mutants restored alkyl hydroperoxide reductase, but catalase was still up-expressed in all complemented strains. The katA promoter sequence was the same in all mutant strains and the wild type. Like its Helicobacter pylori counterpart strain, a H. hepaticus tsaA mutant contained more lipid hydroperoxides than the wild type strain. Hepatic tissue from mice inoculated with a tsaA mutant had lesions similar to those inoculated with the wild type, and included coagulative necrosis of hepatocytes. The liver and cecum colonizing abilities of the wild type and tsaA mutant were comparable. Up-expression of catalase in the tsaA mutants likely permits the bacterium to compensate (in colonization and virulence attributes) for the loss of an otherwise important oxidative stress-combating enzyme, alkyl hydroperoxide reductase. The use of erythromycin resistance insertion as a facile way to screen for gene-targeted mutants, and the chromosomal complementation of those mutants are new genetic procedures for studying H. hepaticus.     

Different isoforms of starch-synthesizing enzymes controlling amylose and amylopectin content in rice (Oryza sativa L.)

Starch, composed of amylose and amylopectin, greatly influences rice cooking and textural quality, which in turn is controlled by various isoforms of several enzymes. Activity of one or more isoforms of starch‐synthesizing enzymes results in various forms of starch structure based on the amylopectin chain length and average external, internal and core chain length distribution and hence results in varying physicochemical and cooking quality. Since the synthesis of starch is highly complex, it is crucial but essential to understand its biosynthetic pathway, starch structure and effects on the physicochemical properties that control eating and cooking quality, and alongside conduct research on gene/QTL mapping for use in marker-assisted selection (MAS) with a view to improve and select cultivars with most desirable range and class of rice starch properties. This article presents the updates on current understanding of the coordination among various enzymes/isoforms towards rice starch synthesis in endosperm and their effect on rice grain physicochemical, cooking and eating qualities. The efforts in identifying regions responsible for these enzymes by mapping the gene/QTLs have provided a glimpse on their association with physicochemical and cooking properties of rice and, hence, improvement is possible by modifying the allelic pattern, resulting in down or nil regulation of a particular enzyme. The clear understanding of the tissue specific coordination between enzyme isoforms and their subsequent effect in controlling eating and cooking properties will enhance the chances to manipulate them for getting desired range of amylose content (AC) and gelatinization temperature (GT) in improved cultivars through combining desired alleles through MAS.     

Pollen morphology of Chinese Curcuma L. and Boesenbergia Kuntz (Zingiberaceae): Taxonomic implications

In order to find new non-molecular evidence to support the phylogenetic and taxonomic position, pollen grains of 20 populations of 16 species of Chinese Curcuma L. and Boesenbergia Kuntz (Zingiberaceae) were investigated under SEM and TEM. The pollen grains are spherical and ovoid, nonaperturate. The pollen wall is composed of a very thin exine and a thick intine. The exine is psilate or echinate. The intine consists of two layers, i.e., a thick, channeled layer (exintine) and an inner homogenous layer (endintine). The results reveal morphological congruence between the pollen grains of species of Curcuma, which according to DNA sequence data appears to be a polyphyletic genus. However the uniform pollen morphology in Curcuma provides no evidence to divide this genus into separate taxonomic entities. Our results on pollen morphology also do not provide any additional evidence to either unite or segregate Boesenbergia albomaculata and Curcumorpha longiflora in the same genus and demonstrate that more taxonomic data on the genus Boesenbergia and its relatives are needed before a final decision can be made.     

An ultrastructural,cytochemical and immunofluorescence study of postmeiotic development of plasmodial tapetum inTradescantia virginiana L. and its relevance to the pathway of sporopollenin secretion

Summary Establishment of a tapetal plasmodium in postmeiotic stages in anther locules ofTradescantia virginiana encloses the tetrads in membrane-limited compartments. The perispore membrane (PSM), around each tetrad, is derived from composite tapetal cell plasma membranes. The tapetum acquires an abundance of ER and ribosomes and by the late tetrad stage the PSM and its underlying cytoplasm exhibit specialized features, studied here by ZnIO impregnation, osmium maceration, application of indirect immunofluorescence employing antitubulin, conventional thin sectioning and the Thiéry reaction. These features include: labyrinthine convolutions of the PSM resulting from migration of membranous sacs and their partial fusion to the PSM, an intimate relationship of tubular ER with the convoluted PSM, and microtubules underlying the PSM and among the membranous sacs. At the same time membrane-bound granules, comparable to but smaller and simpler than tapetal orbicules of secretory tapeta, form in the convolutions. It is postulated that the ER supplies precursors of sporopollenincontaining parts of the spore wall, that the PSM-associated microtubules stabilise the whole secretory apparatus at the tapetum-spore interface, and that the precursors are expelled into the lumen bounded by the PSM and then accreted upon the orbicule-like granules or the developing spore wall. With dissolution of the callosic wall, the plasmodium invades the intermicrosporal spaces of late tetrads, the PSM unfolding its elaborations and becoming closely appressed to the exinous surfaces of individual spores. Microtubules, although present during this phase of invasion, do not seem to propel the invasion processes and may have roles in shape maintenance. During pollen mitosis and enlargement the tapetal cytoplasm accumulates lipidic globules. A late phase of Golgi activity precedes accumulation of vesicles or vacuoles near the spores, these being bounded by single or multiple tripartite membranes. With anther desiccation, portions of plasmodium are deposited on the pollen surface in the form of tryphine, the deposits containing stacked membrane-like bilayers.     

Leishmania tropica: Biochemical aspects of promastigotes' attachment to macrophages in vitro

The in vitro attachment of promastigotes of Leishmania tropica to mouse peritoneal macrophages was studied under experimental conditions. Parasite binding by macrophages required an intact intracellular physiology as suggested by the action of several metabolic inhibitors. Parasite attachment was inhibited in the presence of azide, fluoride, iodoacetamide, and 2-deoxyglucose, but was affected very little by inhibitors of oxidative phosphorylation, by 2,4,-dinitrophenol and by cyanide. Parasite attachment was not prevented by cycloheximide, an inhibitor of protein synthesis. Successful parasite attachment required the simultaneous presence of magnesium, glucose, and a macromolecular component of fetal calf serum in the extracellular medium. Furthermore, glucose and serum supported parasite binding synergistically. The requirement for extracellular glucose could be replaced by mannose, suggesting that such a requirement is structural rather than metabolic. The active fraction of serum was nondialyzable, heat labile, and precipitable by ammonium sulfate. These various chemical ingredients of the culture medium were required mainly during the interaction of parasites with macrophages. The extracellular and metabolic requirements of successful parasite binding suggest that attachment of parasites to macrophages possess the characteristics of a biochemical reaction which is probably mediated by one or more enzymatic reactions.     

Extraction and chemical characterization of starch from S. lycocarpum fruits

In this study the pulp from Solanum lycocarpum fruits was used as raw material for extraction of starch, resulting in a yield of 51%. The starch granules were heterogeneous in size, presenting a conical appearance, very similar to a high-amylose cassava starch. The elemental analysis (CHNS) revealed 64.33% carbon, 7.16% hydrogen and 0.80% nitrogen. FT-IR spectroscopy showed characteristic peaks of polysaccharides and NMR analysis confirmed the presence of the α-anomer of d-glucose. The S. lycocarpum starch was characterized by high value of intrinsic viscosity (3515 mPa s) and estimated molecular weight around 645.69 kDa. Furthermore, this starch was classified as a B-type and high amylose content starch, presenting 34.66% of amylose and 38% crystallinity. Endothermic transition temperatures (T_o = 61.25 °C, T_p = 64.5 °C, T_c = 67.5 °C), gelatinization temperature (ΔT = 6.3 °C) ranges and enthalpy changes (ΔH = 13.21 J g⁻¹) were accessed by DCS analysis. These results make the S. lycocarpum fruit a very promising source of starch for biotechnological applications.