Influences of Cross Pollination on Pollen Tube Growth and Fruit Set in Zuili Plums （Prunus salicina）

Zuili plum （Prunus salicina L.） trees usually set fruit poorly, although they produce high quality fruit. To elucidate the causes of the poor fruit set, pollen tube growth into pistils and fruit set percentage were investigated after cross-, self- and open-pollination. Ovule development in Zuili pistils was also investigated. Pollen tube penetration into the ovules via the obturator and micropyle was best when Zuili pistils were pollinated by cv. Black Amber （P. domestica） pollen grains, although cross-pollinations with Hongxinli and Miili （P. salicina） pollen were more effective than self- and open-pollination. The fruit set percentage was also highest in pistils pollinated with Black Amber pollen grains. Morphological observation of Zuili pistils revealed that the trees produce ＂double pistils＂, developing two ovaries from a basal pistil, at a rate as high as 28%. In such abnormal pistils, most ovules were lacking an embryo sac or were entirely degenerated. The percentage of normally developed ovules was 24.3% and 8.9% in normal and double pistils, respectively. From these results, we conclude that the main causes of poor fruit set of Zuili plums are a lack of effective cross-pollination and the production of high percentages of double pistils in which normally developed ovules are scarcely formed.     

Volatiles from the epicuticular wax of watercress (Rorippa nasturtium-aquaticum)

Volatiles from the epicuticular wax of watercress were collected by ether washing and examined using gas chromatographic and mass spectrometric analysi     

Alkane distribution in epicuticular wax of epacridaceae

Alkane distribution pattern was determined in the epicuticular wax of leaves of 39 species and in the flower wax of three species of Epacridaceae. Uniform patterns were observed within some genera (Monotoca, Styphelia) whereas in others no common pattern was apparent. There was no difference between the alkane patterns of the two subfamilies Epacrideae and Styphelieae. The pattern was not affected by the presence of new growth, and there was no correlation with the season, habitat, climate, nature of soil, or the presence or absence of flowers.     

Chemical composition of the epicuticular and intracuticular wax layers on the adaxial side of Ligustrum vulgare leaves

Previous research has shown that cuticular triterpenoids are exclusively found in the intracuticular wax layer of Prunus laurocerasus. To investigate whether this partitioning was species-specific, the intra- and epicuticular waxes were identified and quantified for the glossy leaves of Ligustrum vulgare, an unrelated shrub with similar wax morphology. Epicuticular wax was mechanically stripped from the adaxial leaf surface using the adhesive gum arabic. Subsequently, the organic solvent chloroform was used to extract the intracuticular wax from within the cutin matrix. The isolated waxes were quantified using gas chromatography with flame ionization detection and identified by mass spectrometry. The results were visually confirmed by scanning electron microscopy. The outer wax layer consisted entirely of homologous series of very-long-chain aliphatic compound classes. By contrast, the inner wax layer was dominated (80%) by two cyclic triterpenoids, ursolic and oleanolic acid. The accumulation of triterpenoids in the intracuticular leaf wax of a second, unrelated species suggests that this localization may be a more general phenomenon in smooth cuticles lacking epicuticular wax crystals. The mechanism and possible ecological or physiological reasons for this separation are currently being investigated.     

Chemistry and micromorphology of compound epicuticular wax crystalloids (Strelitzia type)

Certain non-liliiflorous taxa within the monocotyledons (e.g.,Strelitzia, Heliconia, Typha) are characterized by compound epicuticular wax rodlets (Strelitzia type). Similar rodlets are also encountered on the surface of the dicotyledonous plantBenincasa hispida (Thunb.)Cogn. Chemical analysis of the surface wax from both sources showed that the rodlets are chemically distinct. The rodlets of the monocotyledons consist exclusively of aliphatic wax lipids, mainly wax esters. In contrast, the rodlets ofBenincasa are cheifly composed of triterpenol acetates and triterpenols. Formation of rodlets is therefore interpreted as ultrastructural convergency. It is concluded that taxonomical studies on wax crystalloids can be misleading when interpreted in terms of micromorphology of crystalloids only.     

Seed epicuticular wax of avena sativa

The main fractions in oat seed wax are β-diketones (15.5%), alkanols (14.4%), hydroxy-β-diketones (12.2%), esters (11.1%) and fatty esters (7.2%).     

p-Hydroxybenzaldehyde as a major constituent of the epicuticular wax of seedling Sorghum bicolor

p-Hydroxybenzaldehyde is present in concentrations up to 30% in the wax of Sorghum bicolor seedlings. It is highly deterrent to locusts, reducing their normal feeding by 90%.     

Effect of leaf age on epicuticular wax alkanes in Rhododendron

Alkane distribution pattern in epicuticular wax of Rhododendron fortunei cv Admiral Piet Hein leaves remains unchanged from the age of 6 weeks to abscission.     

Antimicrobial activity in the egg wax of the African cattle tick Amblyomma hebraeum (Acari: Ixodidae)

Eggs of the tick Amblyomma hebraeum Koch (Acari: Ixodidae) inhibited the growth of Escherichia coli and Serratia marcescens (Gram-negative bacteria) in solid culture, but not the growth of Staphylococcus epidermidis, and only marginally the growth of Bacillus subtilis (Gram-positive bacteria). When egg wax was extracted with chloroform/methanol (2:1), the extract contained antibacterial activity, but the denuded eggs did not. When assayed against bacteria in liquid culture, the aqueous phase inhibited the growth of S. epidermidis. However, the activity against E. coli was lost during extraction. The antimicrobial component of the aqueous phase was heat stable (100°C for 10 min), resistant to proteinase K (15 min at 55°C) and to pronase (30 min at 37°C). The antibacterial activity in the aqueous phase increased the permeability of the cell membrane of susceptible bacterial cells within 30 min. However, lysis of the cells was detected by optical density measurements (OD_{600 nm}) only after 1.5 h. The most evident cytological changes observed by transmission electron microscopy were a thickening of the cell wall and the appearance of numerous electron lucent areas within the cytoplasm of treated bacteria. Gené’s organ, the egg-waxing organ in ticks, grew enormously during the first 16 days post-engorgement, and gained antimicrobial activity by day 10 (when oviposition began). This suggests that Gené’s organ is the major source of the antibacterial substance in the egg wax. The vitellogenic hormone in A. hebraeum, 20-hydroxyecdysone, when injected into recently engorged females, did not stimulate growth of Gené’s organ or precocious secretion of antimicrobial activity.     

UV-B辐射增强对拟南芥表皮蜡质的影响

以野生型拟南芥、蜡质不同程度缺失突变体CER1、CER3、CER4、CER6、CER10、CER20及KCS1为试验材料,通过施加50μW/cm2、长达10 d的UV-B辐射,研究了拟南芥表皮蜡质晶体结构、组分及蜡质基因对UV-B辐射的响应机制。结果表明:UVB辐射增强改变了拟南芥表皮蜡质晶体结构,表皮蜡质松针状(CER1)、柱状、杆状(CER3、CER10与KCS1)晶体结构显著减少,球状蜡质晶体类型出现在CER6表面,无规则片状、膜状结构覆盖在KCS1与CER10茎表面。野生型拟南芥蜡质晶体结构类型无明显变化,但在部分区域积累了大量水平杆状、管状结构,增加了蜡质层厚度。UV-B辐射增强也改变了拟南芥表皮蜡质组分的分泌量。野生型在UV-B处理后一级醇、酸、醛含量显著上升,烷、次级醇及酮含量显著下降,蜡质总量增加不显著。一级醇含量的增加及酮和次级醇含量的减少在拟南芥各材料响应UV-B辐射中具有普遍性。UV-B辐射增强诱导了野生型CER3、CER4、KCS1基因表达的上调,其中CER4大量表达,促进了蜡质组分中一级醇、酸和醛含量的积累;CER1在UV-B处理后表达量下调,可能导致烷合成下游分支途径相关产物(烷类、次级醇及酮类)的减少。WIN1表达量的下调对蜡质总量没有显著影响。UV-B辐射增强使蜡质前体从烷合成分支途径更多地转向一级醇分支途径。     

Effects of light and temperature on the composition of epicuticular wax of barley leaves

The amount of wax/cm² on expanding primary leaves of Bonus barley depends on both the photo- and thermoperiods in which the seedlings are grown. With a temperature cycle of 15–10°, transfer of dark grown leaves to the light stopped leaf expansion and after 24 hr yielded 2·5 times more wax/cm² than is characteristic for light grown leaves. This demonstrates that wax synthesis and extrusion is not directly correlated with leaf expansion. The relative amounts of the wax classes formed by the decarboxylation pathways (< 1%), the reductive pathways (89%) or only by elongation (10%) are the same in light and dark. Within the reductive pathways, however, light stimulates aldehyde formation. Both environmental parameters can strongly influence the chain length composition of the wax classes. In the light one chain length or one group of chain lengths dominates a given wax class. In the dark two prominent chain lengths or groups thereof are found. The major chain length in these two groups differs by two or more carbons.     

Effects of foliar sprays containing calcium, magnesium and titanium on plum (Prunus domestica L.) fruit quality

An experiment was performed in which Ti⁴⁺-ascorbate was sprayed onto plum trees in several combinations with other commercial compounds containing Ca²⁺ and Mg²⁺ to study the effects on the commercial quality of fruits, with special focus on improving their resistance against postharvest handling damage.

All the treatments containing titanium increased the tree performance (branch elongation, flowering and fruit setting intensities) and fruit size. At harvest fruits from the Ti-treated trees showed improved resistance to compression and penetration, as well as a decrease in weight-loss during postharvest storage. A similar response was obtained for the external colour, though all the treatments seemed to delay somewhat the apparent ripening status. Nevertheless, the fruits from Ti-treated trees showed a better behaviour in the evolution of the colour parameters during storage than did the control fruits.

Titanium application significantly increased the calcium, iron, copper and zinc concentrations in peel and flesh. This improvement in the calcium absorption is explained as a consequence of the beneficial effect of titanium on the absorption, translocation and assimilation processes.     

Characterization,purification, and temperature/pressure stability of polyphenol oxidase extracted from plums (Prunus domestica)

In this study, polyphenol oxidase (PPO) was extracted from Prunus domestica and partially purified by ammonium sulfate precipitation, hydrophobic interaction chromatography, and ion exchange chromatography. The final purification step revealed a 32.81-fold purification, and the molecular mass was estimated to be 65 kDa by SDS-PAGE. The purified PPO showed enzymatic activity mainly toward five substrates, namely catechol, catechin, 4-methyl catechol, chlorogenic acid, and L-3,4-dihydroxyphenylalanine, whereas it showed no activity toward caffeic acid, ferulic acid, p-coumaric acid, p-cresol, and l-tyrosine. The optimum pH and temperature values were 6.0 and 25 °C, respectively. The enzyme showed high stability in the pH range of 5.0–7.0 and in the temperature range of 25–65 °C. The most effective inhibitors of this enzyme were found to be ascorbic acid and l-cysteine. The thermal inactivation followed a first-order kinetic model, with activation energy of E_a 150.46 ± 1.29 kJ/mol. PPO extracted from plum showed stability at high pressure, with enzyme activation at 500 MPa.     

Characterization of an alkylresorcinol synthase that forms phenolics accumulating in the cuticular wax on various organs of rye (Secale cereale)

Alkylresorcinols are bioactive compounds produced in diverse plant species, with chemical structures combining an aliphatic hydrocarbon chain and an aromatic ring with characteristic hydroxyl substituents. Here, we aimed to isolate and characterize the enzyme that forms the alkylresorcinols accumulating in the cuticular wax on the surface of all above‐ground organs of rye. Based on sequence homology with other type‐III polyketide synthases, a candidate alkylresorcinol synthase was cloned. Yeast heterologous expression showed that the enzyme, ScARS, is highly specific for the formation of the aromatic resorcinol ring structure, through aldol condensation analogous to stilbene synthases. The enzyme accepts long‐chain and very‐long‐chain acyl‐CoA starter substrates, preferring saturated over unsaturated chains. It typically carries out three rounds of condensation with malonyl‐CoA prior to cyclization, with only very minor activity for a fourth round of malonyl‐CoA condensation and cyclization to 5‐(2′‐oxo)‐alkylresorcinols or 5‐(2′‐hydroxy)‐alkylresorcinols. Like other enzymes involved in cuticle formation, ScARS is localized to the endoplasmic reticulum. ScARS expression patterns were found correlated with alkylresorcinol accumulation during leaf development and across different rye organs. Overall, our results thus suggest that ScARS synthesizes the cuticular alkylresorcinols found on diverse rye organ surfaces.     

Volatile emission of different plant parts and fruit development from Italian cherry plums (Prunus cerasifera and P. cerasifera ‘Pissardii’)

The chemical composition of volatiles emitted in vivo from different plant parts of P. cerasifera and P. cerasifera ‘Pissardii’ were collected during the entire biological cycle of the plant growth and analyzed by gas chromatography mass spectrometry (GC-MS) after solid phase micro-extraction (SPME). All the data were submitted to multivariate statistical analysis evidencing many differences amongst the selected plant parts and growth stages. A total of 136 compounds were identified corresponding to 90.1–99.6% of the whole aroma profile of cherry plum samples. Non-terpenes were the most abundant class of constituents present in the volatile emission of all analyzed samples. In particular, the aroma of both fruit stages was mainly characterized by alcohols and esters in different amounts.     

Slippery ant-plants and skilful climbers: selection and protection of specific ant partners by epicuticular wax blooms in Macaranga (Euphorbiaceae)

 In many ant-plant species of the genus Macaranga in South-East Asia, conspicuous blooms of epicuticular wax crystals cover the stem surface. We found that many ant species were unable to walk on these surfaces. Only the specific ant partners of glaucous Macaranga host plants were capable of moving on the slippery stems without difficulty. Therefore, the epicuticular coatings of Macaranga myrmecophytes appear to have a selective function and protect the associated ants against competitors. The epicuticular aggregates function as a physical barrier; no evidence of chemical repellence was found. The extent to which ”foreign” ant species are excluded from a tree strongly depends on inclination, diameter and length of the glaucous stem sections. The particular growth form of some glaucous Macaranga ant-plants enhances the influence of the wax barriers. The ant associates of glaucous and glossy Macaranga ant-plants (genera Crematogaster and Camponotus) differ strongly in their capacity to adhere to the glaucous stems. For this reason, the wax blooms in Macaranga can act as an ecological isolation mechanism for the sympiotic ants. Within the genus Macaranga, we find a high correspondence between the occurrence of glaucousness and obligatory ant association (50% in ant-plants; 6.7% in non-myrmecophytes). The genus Macaranga thus represents one of the few cases known so far where epicuticular wax crystals are likely to have evolved in relation to insects. Received: 2 January 1997 / Accepted: 9 June 1997