The impact of mechanical impedance on the emergence of carrot and onion seedlings

The development of a method using wax layers to simulate the effect of strong soil crusts on seedling emergence is described. Wax layers of different strengths were prepared by melting together white soft paraffin and paraffin wax in different proportions. The wax discs were placed above seeds planted in wet, but well-aerated sand in controlled environments. The effect of adding charcoal to the wax discs to prevent transmission of light was also tested. When wax layer penetrometer pressure was 0.2–0.25 MPa, light transmission greatly decreased the final emergence of carrot, but not onion seedlings. Penetrometer pressures above 0.25 MPa greatly decreased emergence through black wax layers in both carrot and onion. The presence of 2–4 mm stones immediately below wax layers (to simulate aggregates) decreased the emergence of onion shoots through wax layers with penetrometer pressures of 0.25 MPa and above. The emergence of carrot and onion seedlings from wax layers was compared to emergence in the field from different soil types and aggregate sizes. In both laboratory and field experiments, carrot gave better emergence than onion when emergence was relatively poor. Results were consistent with the hypothesis that mechanical impedance is a major factor in poor crop emergence in temperate conditions.     

Convergent maternal provisioning and life-history evolution in echinoderms

In marine invertebrates, the frequent evolution of lecithotrophic nonfeeding development from a planktotrophic feeding ancestral developmental mode has involved the repeated, independent acquisition of a large, lipid-rich, usually buoyant egg. To investigate the mechanistic basis of egg-size evolution and the role of maternally provisioned lipids in lecithotrophic development, we identified and quantified the egg lipids in six sea urchin species and five sea star species encompassing four independent evolutionary transformations to lecithotrophy. The small eggs of species with planktotrophic development were dominated by triglycerides with low levels of wax esters, whereas the larger eggs of lecithotrophs contain measurable triglycerides but were dominated by wax ester lipids, a relatively minor egg component of planktotrophs. Comparative analysis by independent contrasts confirmed that after removing the influence of phylogeny, the evolution of a large egg by lecithotrophs was correlated with the conspicuous deposition of wax esters. Increases in wax ester abundance exceeded expectations based solely on changes in egg volume. Wax esters may have roles in providing buoyancy to the egg and for postmetamorphic provisioning. Experimentally reducing the amount of wax esters in blastula stage embryos of the lecithotroph Heliocidaris erythrogramma resulted in a viable but nonbuoyant larvae. During normal development for H. erythrogramma, wax ester biomass remained constant during development to metamorphosis (five days postfertilization), but decreased during juvenile development before complete mouth formation (12 days postfertilization) and was further reduced at 18 days postfertilization. The function of wax esters may be specific to the lecithotrophic developmental mode because there were negligible wax esters present in competent pluteus larvae of Strongylocentrotus drobachiensis, a planktotrophic species. These data suggest that this seminal evolutionary modification, the production of a large egg, has been accomplished in part by the elaboration of a preexisting oogenic component, wax esters. The modification of preexisting oogenic processes may facilitate the observed high frequency of transformations in larval mode in marine invertebrates.     

Mutants in Arabidopsis thaliana Altered in Epicuticular Wax and Leaf Morphology

We report eight new mutants in Arabidopsis thaliana possessing altered leaf morphology and epicuticular wax. These were isolated from a T-DNA-mutagenized population using a visual screen for altered leaf reflectance, i.e. increased glaucousness or glossiness. The mutants were placed into three distinct classes based on alterations in overall plant morphology: knobhead (knb), bicentifolia (bcf), and wax. The four knb mutants formed callus-like growths in the axillary region of the rosette leaves and apical meristem, the two bcf mutants produced hundreds of narrow leaves, and the two wax mutants had leaves and stems that were more glossy than wild type and organs that fused during early development. Leaves of knb and bcf were more glaucous and abnormally shaped than wild type. Epicuticular wax crystals over knb and bcf leaf surfaces (where none were present on wild type) likely contributed to their more glaucous appearance. In contrast, the glossy appearance of the wax mutants was associated with a reduced epicuticular wax load on both leaves and stems. One representative from each phenotypic class was selected for detailed analyses of epicuticular wax chemistry. All three lines, knb1, bcf1, and wax1, had dramatic alterations in the total amounts and relative proportions of their leaf epicuticular wax constituents.     

大蜡螟防控技术研究进展

大蜡螟Galleria mellonella L.是蜂群中普遍存在的害虫,其幼虫蛀毁巢脾,造成封盖蛹不能孵化出房,使蜂群群势下降甚至飞逃.当前,大蜡螟作为试验昆虫受到越来越多的关注,而其防控技术的研究相对薄弱,蜡螟危害仍是限制养蜂发展的因素之一.本文对国内外大蜡螟的防控技术进行了梳理总结,为我国制定蜡螟综合防控措施提供...     

Development of the cuticular wax during growth of Kalanchoe daigremontiana (Hamet et Perr. de la Bathie) leaves

The goal of the present study was to monitor cuticular wax accumulation during leaf development of Kalanchoe daigremontiana . Leaves expanded linearly until they were 40–60 d old. Wax coverages of leaves on the third node increased steadily during initial leaf development, from 6.5  µ g·cm⁻² on day 22 to 15.3  µ g·cm⁻² on day 53, and then levelled off. Triterpenoids dominated the wax mixture throughout leaf development, but decreased from 74 to 40–45% in mature leaves, while very long-chain fatty acid (VLCFA) derivatives increased from 19 to 39–44%. The major VLCFA derivatives were alkanes, accompanied by fatty acids, primary alcohols, aldehydes and alkyl esters. In all compound classes, either C₃₄ or C₃₃ homologs predominated during leaf development. Eight different triterpenoids were identified, with glutinol constituting 70% of the fraction, and friedelin (20%) and germanicol (10%) as further major components of the young leaf wax. The glutinol percentage decreased, while the relative amounts of epifriedelanol and glutanol increased during development. Various leaf pairs upwards from the third node showed similar growth patterns and developmental time courses of cuticular wax amounts and composition. Based on these surface chemical analyses, the relative activities of biosynthetic pathways leading to various wax components can be assessed.     

“Natural” and NH3-induced variation in epicuticular needle wax morphology of Pseudotsuga menziesii (Mirb.) Franco

Summary Changes in epicuticular wax morphology of Pseudotsuga menziesii needles were studied with scanning electron microscopy throughout the growing season in current-year and older needles in 20 trees from two sites, Kootwijk and Garderen (The Netherlands). Fusion of crystalline wax rods leading to a reticulate structure and ultimately to degradation of the regular three-dimensional porous structure started several weeks after bud break and reached a high level at the end of the first growing season. The increase in amorphous (solid) wax showed a similar, but slightly slower development. In 1- and 2-year-old needles the degradation of crystalline wax and increase in amorphous wax had progressed only slightly further. The rates of change in crystalline wax morphology were very similar for sun-exposed and shaded needles, for the two sites, and for the two tree vitality classes included in the samples. The development of epiphyllous fungi also appeared to be largely needle age dependent. The effects of NH₃ on needle wax morphology were studied in young trees used in fumigation experiments. Short-term fumigation (approx. 5 weeks) did not affect wax morphology in current-year needles, but 1-year-old needles which had been exposed to different concentrations from bud break onwards showed a severe degradation of the crystalline wax, regardless of the NH₃ concentration used. In 2-yearold needles the effect of NH₃ could not be traced and was overshadowed by the natural ageing process. Ambient O₃, SO₂ and NO_x levels did not effect epicuticular wax morphology. It is suggested that the variation recorded for the two forest stands does not show effects of local pollution levels.     

Leaf wax n-alkane δD values are determined early in the ontogeny of Populus trichocarpa leaves when grown under controlled environmental conditions

The stable hydrogen isotope ratios (δD) of leaf wax n-alkanes record valuable information on plant and ecosystem water relations. It remains, however, unknown if leaf wax n-alkane δD values record only environmental variation during the brief period of time of leaf growth or if leaf wax n-alkane δD values are affected by environmental variability throughout the entire lifespan of a leaf. To resolve these uncertainties, we irrigated Populus trichocarpa trees with a pulse of deuterium-enriched water and used compound-specific stable hydrogen isotope analyses to test if the applied tracer could be recovered from leaf wax n-alkanes of leaves that were at different stages of their development during the tracer application. Our experiment revealed that only leaf wax n-alkanes from leaves that had developed during the time of the tracer application were affected, while leaves that were already fully matured at the time of the tracer application were not. We conclude from our study that under controlled environmental conditions, leaf wax n-alkanes are synthesized only early in the ontogeny of a leaf. Our experiment has implications for the interpretation of leaf wax n-alkane δD values in an environmental context, as it suggests that these compounds record only a brief period of the environmental variability that a leaf experiences throughout its life.     

Screening the ability of rice roots to overcome the mechanical impedance of wax layers: importance of test conditions and measurement criteria

The development of a wax layer method for screening the ability of rice (Oryza sativa L.) roots to overcome mechanical impedance is described. Wax layers (3 mm thick) made of mixtures of white soft paraffin and paraffin wax were installed 50 mm deep in tubes of sand. The sand was watered with nutrient solution and planted with 3-d old rice seedlings. The numbers of root axes per plant that had penetrated the wax layers 24 d after planting were counted. The ratio of penetrated to total root axes per plant gave a misleading measure of root penetration ability, as rice varieties differed in the ratio of penetrated to total axes in a low impedance (3% wax) control. In non-flooded conditions, a 60% wax layer decreased root penetration (number of roots penetrating the wax layer per plant) to a mean of 74% of the low impedance control, whereas an 80% wax layer decreased mean root penetration to 31% of the control. The best measure of root penetration in non-flooded conditions was the number of axes penetrating an 80% wax layer. Flooding decreased root penetration of a 60% wax layer to a mean of 26% of the low impedance control. The best measure of root penetration in flooded conditions was the number of axes penetrating a 60% wax layer.     

南洋臀纹粉蚧雌成虫主要器官及其蜡泌物的扫描电镜观察

为明确南洋臀纹粉蚧Planococcus lilacinus(Cockerell)雌成虫及其蜡泌物的结构特征,利用扫描电镜观察该虫体表主要器官、蜡质及泌蜡腺体的超微结构.结果表明:南洋臀纹粉蚧雌成虫外覆白色粉状厚蜡被,体缘具18对蜡棒,触角8节、口器和足发达且分布有不同长度的毛形和刺形感受器,眼为单眼,腹脐和背孔唇形、...     

Light-independent and dependent phases of proplastid development in Euglena gracilis W3BUL

Cells of Euglena gracilis Klebs var. bacillaris Cori mutant W3BUL grown in darkness on Hutner's pH 3.5 medium without agitation accumulate wax ester. These cells have undeveloped proplastid remnants characteristic of this mutant. If these cells are transferred to an inorganic medium and bubbled with 2-3% CO2 in air, the wax disappears and the proplastid expands and develops in darkness to form prolamellar bodies and membrane vessicles within 96 h. No further development takes place in darkness, but if these cultures are illuminated at 96 h formation of prothylakoids is observed. Thus the wax ester accumulated during growth can be used subsequently to support proplastid development up to the prolamellar body stage, but the formation of prothylakoids is strictly light-dependent. Development in this system takes place at a slower rate than in cells grown with shaking and lacking wax which are transferred to resting medium. As previously shown, all of proplastid development requires light under these conditions. It is suggested that the oxygen-requiring utilization of wax in darkness can provide energy and metabolites for a part of proplastid development but the later steps in these cells, or the entire development in cells lacking wax is supported by paramylum degradation which is strictly light-dependent. However, a specific light reaction required for prothylakoid organization is not ruled out.     

Development and properties of a wax ester hydrolase in the cotyledons of jojoba seedlings

The activity of a wax ester hydrolase in the cotyledons of jojoba (Simmondsia chinensis) seedlings increased drastically during germination, parallel to the development of the gluconeogenic process. The enzyme at its peak of development was obtained in association with the wax body membrane, and its properties were studied. It had an optimal activity at alkaline pH (8.5-9). The apparent K_m value for N-methylindoxylmyristate was 93 μM. It was stable at 40 C for 30 min but was inactivated at higher temperature. Various divalent cations and ethylenediaminetetraacetate had little effect on the activity. p-Chloromercuribenzoate was a strong inhibitor of the enzyme activity, and its effect was reversed by subsequent addition of dithiothreitol. It had a broad substrate specificity with highest activities on monoglycerides, wax esters, and the native substrate (jojoba wax).     

角倍蚜各虫态蜡腺的分布与结构

[目的]角倍蚜Schlechtendalia chinensis是五倍子的主要生产种,具有复杂的生活史,需要经历干母、干雌、秋迁蚜、越冬若蚜、春迁蚜和性蚜6种虫态,在盐肤木Rhus chinensis和藓类植物上转主寄生,经历有性和无性生殖、瘿内和瘿外世代的交替才能完成生活史.通过对角倍蚜蜡腺的研究,有助于深入了解角倍...     

Internal and external photoprotection in developing leaves of the CAM plant Cotyledon orbiculata

Leaves of the CAM plant Cotyledon orbiculata produced a dense epidermal wax which decreased the absorption of light, possibly functioning as an external photoprotective mechanism (Robinson et al. 1993). However, developing leaves did not accumulate wax until after 21 d with full wax coating not achieved until at least 35 d. In addition, young leaves had lower rates of electron transport than mature leaves. Leaf development therefore occurs at higher incident PFD than that experienced by the mature leaves, and, for young leaves, can lead to an increase in the proportion of light energy which is excess to requirements and must be dissipated non-photochemically. Changes in the photosynthetic capacity, PSII efficiency, rate of energy dissipation, and the content of chlorophyll (Chi), carotenoids, wax and anthocyanins were followed in developing leaves of C. orbiculata in an attempt to elucidate the relative importance of the various photoprotective mechanisms during leaf ontogeny. The largest pools of xanthophyll cycle pigments (on a Chi basis) were found in the waxless, young leaves and were correlated with greater levels of energy dissipation activity. The importance of xanthophyll cycle-dependent energy dissipation in young C. orbiculata leaves prior to development of a reflective wax covering, and full photosynthetic capacity which for CAM plants includes appreciable nocturnal acid accumulation, is discussed. Also, we consider the possibility that anthocyanin pigments in the upper and lower epidermis may increase reflectivity and act as external photoprotectants.     

Ontogenetic and seasonal development of wax composition and cuticular transpiration of ivy (Hedera helix L.) sun and shade leaves

The ontogenetic and seasonal development of wax composition and cuticular transpiration of sun and shade leaves of ivy (Hedera helix L.) was analysed by investigating leaves varying in age between 4 and 202 d. It was discovered that the total amount of solvent-extractable wax was composed of two distinct fractions, separable by column chromatography: (i) a less polar or apolar monomeric wax fraction consisting of the typical linear, long-chain aliphatics usually described as cuticular wax components and (ii) a polar, oligomeric wax fraction consisting of primary alcohols and acids mostly esterified to C₁₂-, C₁₄- and C₁₆-ω-hydroxyfatty acids. The apolar wax fraction, which could be analysed directly by gas chromatography coupled with mass spectrometry (GC-MS), exhibited pronounced seasonal changes in composition. Wax amounts in the apolar fraction reached a maximum after about 30 d and gradually decreased again during the remaining period of the season investigated. In contrast, the polar wax fraction, which was analysable by GC-MS only after transesterification, rapidly increased early in the season, reaching a plateau after 40 d, and then remained constant during the rest of the season. Thus, total amounts of solvent-extractable cuticular waxes, which can be determined gravimetrically, will only be detected by GC-MS after fractionation and transesterification, a methodological approach rarely applied in the past in cuticular wax analysis. Additionally, investigation of the cutin polymer matrix after depolymerisation through transesterification, revealed that only those primary alcohols and acids forming an essential part of the apolar and the polar wax fractions were esterified during the investigated season and incorporated in increasing amounts into the cutin polymer matrix (matrix-bound wax fraction). Thus, it can be concluded that a complete analysis of cuticular wax of ivy and its seasonal development can only be achieved if all the relevant fractions (i) the less polar or apolar, (ii) the polar and (iii) the wax fraction bound to the cutin polymer matrix are investigated. Cuticular transpiration rapidly decreased within the first 30 d and essentially remained constant during the rest of the season. Thus, changes in cuticular water permeability were closely correlated with the most prominent changes in wax amounts and composition occurring during the first 30 d of ontogenetic leaf development. However, during the remainder of the year, up to 202 d, cuticular transport properties remained constant, although significant quantitative and qualitative changes in cuticular wax composition continued to occur. Thus, our study clearly demonstrated that there will be no simple relationship between chemical composition of cuticular waxes and transport properties of isolated ivy leaf cuticles. Received: 2 March 1998 / Accepted: 26 June 1998     

绞股蓝果实的发育解剖学研究

应用石蜡切片和扫描电镜的方法,观察了绞股蓝果实与种子的发育过程,结果表明:花后12 d左右,绞股蓝合子开始进行第一次分裂,极核分裂在花后6～7 d,核型胚乳在胚的发育中被吸收,胚的发育为茄型,外珠被呈网格状花纹。假果,表面有蜡质,果壁可明显分为3层,内侧细胞后期解体,种子倒三角形,表面瘤状突起。脱落花果的结构表现为珠被萎缩和胚发育受阻。     

角蜡蚧和日本龟蜡蚧蜡泌物的超微结构及化学成分分析

采用扫描电镜和气相色谱/质谱联用技术研究了角蜡Ceroplastes ceriferus (Fabricius) 和日本龟蜡蚧C. japonicus Green蜡泌物的超微结构及化学成分。结果表明,这2种蜡蚧分泌蜡质和形成蜡壳的过程基本相似。在1、2龄期分泌的蜡质为“干蜡”,蜡壳为星芒状,虫体周缘的蜡芒均为2大节,与其2个龄期发育相对应,每一个大节又分为若干小节。同时,虫体背面中央蜡质堆积成帽状,也分为均匀的多层。由此说明泌蜡过程具有节律性。虫体周缘与蜡芒对应的突起区上分布着密集的刻点状腺孔,每一个腺孔分泌1根蜡丝,这在以往玻片标本中是观察不到的。雌性第3龄幼虫和成虫期,虫体分泌“湿蜡”,形成龟背状蜡壳,泌蜡腺孔主要为三格腺和四格腺。在肛突区发现了密集的泌蜡腺孔,排列为纵条纹状。从角蜡蚧蜡泌物甲酯化处理样品中检测到14个组分,从直接测试 (未经甲酯化处理) 样品中检测到14个组分;而从日本龟蜡蚧则分别检测到10个组分和25个组分。它们的主要成分是一系列高级的长链饱和与不饱和的烃、脂肪酸、脂肪醇、酯类、醛类以及杂环、多环或大环状化合物。对它们可能的生物生态学功能进行了讨论。     

应用Steedman's wax 切片法观察植物细胞微管骨架

微管骨架在植物发育过程中起重要作用。由于植物细胞的特殊性,与动物细胞相比植物微管骨 架的研究遇到更多的困难。简略地介绍了曾被国内外学者应用的植物微管骨架的各种研究方法及其局限 性。Steedman's wax是一种多脂蜡。它熔点低(35~37℃),具有与石蜡相同的切片性质,能够切成不同厚 度的连续切片,适合深埋于器官内部的组织或细胞的免疫细胞化学研究。介绍了应用Steedman's wax 切 片法观察植物细胞微管骨架的一般程序和方法以及经过作者检验且切实可行的一些技术改进。     

Relationship Between Cuticular Waxes and Storage Quality Parameters of Korla Pear Under Different Storage Methods

Cuticular wax is an important factor that affects storage quality of fruits and vegetables. Previous studies have shown that cuticular wax of pears changes significantly during storage, whereas there are few studies on the effects of different storage methods on the wax changes and the relationship with storage quality. Cuticular wax of Korla pear stored using different methods, was measured to analyze its total wax content, chemical compositions and their relationship with storage quality. At the end of storage, the highest cuticular wax content was observed in controlled atmosphere (CA) storage and the lowest in room temperature storage. The substances of the primary components with higher contents were nonacosane, (E, E)-ɑ-farnesene, dodecan-1-ol, 1,1-dimethoxynonane, nonanal, palmitic acid, and oleic acid. Total wax content, olefins and fatty acids were most significantly with the storage quality, followed by alkanes and esters. Moreover, total wax content, wax composition and weight loss were closely related to postharvest senescence. Overall, an understanding of variations in the cuticular wax under different storage methods could provide theoretical basis for further study on the storage and preservation technology of pears.

     

Changes in leaf cuticular waxes of sesame (Sesamum indicum L.) plants exposed to water deficit

Sesame (Sesamum indicum L.) is one of the most important oilseed crops, having seeds and oil that are highly valued as a traditional health food. The objective of this study was to evaluate leaf cuticular wax constituents across a diverse selection of sesame cultivars, and the responses of these waxes to drought-induced wilting. Water-deficit was imposed on 18 sesame cultivars by withholding irrigation for 15d during the post-flowering stage, and the effect on seed yield and leaf waxes compared with a well-watered control. Leaf cuticular waxes were dominated by alkanes (59% of total wax), with aldehydes being the next-most abundant class. Compared to well-irrigated plants, drought treatment caused an increase in wax amount on most cultivars, with only three cultivars having a notable reduction. When expressed as an average across all cultivars, drought treatment caused a 30% increase in total wax amount, with a 34% increase in total alkanes, a 13% increase in aldehydes, and a 28% increase in the total of unknowns. In all cultivars, the major alkane constituents were the C27, C29, C31, C33, and C35 homologs, whereas the major aldehydes were the C30, C32, and C34 homologs, and drought exposure had only minor effects on the chain length distribution within these and other wax classes. Drought treatments caused a large decrease in seed yield per plant, but did not affect the mean weight of individual seeds, showing that sesame responds to post-flowering drought by reducing seed numbers, but not seed size. Seed yield was inversely correlated with the total wax amount (-0.466*), indicating that drought induction of leaf wax deposition does not contribute directly to seed set. Further studies are needed to elucidate the ecological role for induction of the alkane metabolic pathway by drought in regulating sesame plant survival and seed development in water-limiting environments.     

Submersed Culture Production of Extracellular Wax Esters by the Marine Bacterium <Emphasis Type="Italic">Fundibacter jadensis</Emphasis>

Fundibacter jadensis strain T9, a marine gram-negative bacterium, was isolated from the intertidal sediment of the German North Sea coast by our group. The cells were able to produce considerable amounts of extracellular wax esters when cultivated with n-alkanes (hexadecane or tetradecane) as a carbon source. The dependence of wax ester production and the composition of the purified wax on different culture conditions (C:N:P ratio and dissolved oxygen tension) were tested. Our results show that wax ester production was not directly growth-linked. The C:N:P ratio had no significant influence on the yield of alkane-free purified wax. The dissolved oxygen tension affected the produced amount of the alkane-free purified wax and the composition of the purified wax; when lower than 2% it decreased the yield of purified wax and led to an altered wax ester composition. Tetradecane as a carbon source enhanced the spectrum of the wax ester composition.