The control of food mobilisation in seeds of Cucumis sativus L.

The development of maximal rates of lipid and protein hydrolysis in cucumber cotyledons depends upon the removal of the testa and the presence of the embryonic axis. The testa appears to exert at least part of its inhibitory influence by suppressing the development of enzyme activity associated with lipolysis and proteolysis. There is, however, no evidence to suggest that the presence of the embryonic axis is a pre-requisite for the development of optimal enzyme activity.Abbreviations TLC thin layer chromatography - GC-MS gas chromatography-mass spectrometry - GLC gas-liquid chromatography - TCA trichloroacetic acid     

No influence of the embryonic axis on the development of diamine oxidase in pea cotyledons

A reexamination has been made for the supposed regulation of pea (Pisum sativum cv Alaska) cotyledonary diamine oxidase (EC 1.4.3.6) activity by the embryonic axis. When dry cotyledons from which the embryo and testa have been removed surgically are imbibed by soaking in water, there is little increase of the enzyme activity during subsequent incubation on filter paper. However, if the dry cotyledons are imbibed and maintained on filter paper from the first, the increase of the enzyme activity is similar to that in the intact seedling. Thus, rapid imbibition of the isolated dry cotyledons is responsible for repression of enzyme development, and a role for the axis need not be invoked.     

Physical forces in dormancy and germination of xanthium seeds

The germination of seeds of Xanthium pensylvanicum Wallr. occurs in 2 phases, an initial passive phase of water uptake followed by an active phase of growth. These 2 phases have been separated experimentally, and shown to occur similarly in isolated cotyledons and embryonic axes. Measurements of the physical thrust generated by the entire seed and its separate components of cotyledon and axis reveal that non-dormant Xanthium seeds develop more than twice the thrust of dormant seeds, and that this difference develops principally in the second phase of enlargement of the axis. Measurement of the forces required for piercing the testa of these seeds establishes that whereas the thrust developed by non-dormant seed is adequate to cause testa rupture, that developed by dormant seeds is not. It is concluded that the dormancy of Xanthium involves an inadequacy in the embryo for rupture of the testa.     

Water Relations of Seed Development and Germination in Muskmelon (Cucumis melo L.) : IV. Characteristics of the Perisperm during Seed Development

We previously reported that an apparent water potential disequilibrium is maintained late in muskmelon (Cucumis melo L.) seed development between the embryo and the surrounding fruit tissue (mesocarp). To further investigate the basis of this phenomenon, the permeability characteristics of the tissues surrounding muskmelon embryos (the mucilaginous endocarp, the testa, a 2- to 4-cell-layered perisperm and a single cell layer of endosperm) were examined from 20 to 65 days after anthesis (DAA). Water passes readily through the perisperm envelope (endosperm + perisperm), testa, and endocarp at all stages of development. Electrolyte leakage (conductivity of imbibition solutions) of individual intact seeds, decoated seeds (testa removed), and embryos (testa and perisperm envelope removed) was measured during imbibition of freshly harvested seeds. The testa accounted for up to 80% of the total electrolyte leakage. Leakage from decoated seeds fell by 8- to 10-fold between 25 and 45 DAA. Presence of the perisperm envelope prior to 40 DAA had little effect on leakage, while in more mature seeds, it reduced leakage by 2- to 3-fold. In mature seeds, freezing, soaking in methanol, autoclaving, accelerated aging, and other treatments which killed the embryos had little effect on leakage of intact or decoated seeds, but caused osmotic swelling of the perisperm envelope due to the leakage of solutes from the embryo into the space between the embryo and perisperm. The semipermeability of the perisperm envelope of mature seeds did not depend upon cellular viability or lipid membrane integrity. After maximum seed dry weight is attained (35-40 DAA), the perisperm envelope prevents the diffusion of solutes, but not of water, between the embryo and the surrounding testa, endocarp, and mesocarp tissue.     

Taxonomic value of seed characters in the Erica tetralix L. group (Ericaceae)

A study of the seed morphology of Erica tetralix and the related species E. mackaiana and E. andevalensis was performed to evaluate the taxonomic importance of seed characters. Size and shape of seeds and surface cells were studied, and area, perimeter, main axis lengths, elongation and sinuosity were measured. Levels of intraspecific variation were considered by means of nested analysis of variance. The study of the intraspecific variation of the characters shows significant differences for lower levels, higher than variations between species for most characters. Levels of variation must be based upon the numerical analysis of seed characters for a correct approach to determining systematic value. E. mackaiana and E. andevalensis group together versus E. tetralix for sinuosity of testa cells. This is a good taxonomic character because it shows significant differences between species and no significant differences between populations. E. tetralix has strongly undulated testa cells while E. mackaiana and E. andevalensis have slightly undulated or curved testa cells. These two species can be discriminated by size of the seed, with seeds of 0.37-0.38 mm for E. andevalensis and 0.4 - 0.45 mm for E. mackaiana. Similarities are found in seed morphology for E. mackaiana and E. andevalensis, but we nevertheless consider the species status for the three taxa as the most natural taxonomic assignment. A key to the species is provided.     

The Role of ABA in the Control of Apple Seed Dormancy Re-appraised by Combined Gas Chromatography-Mass Spectrometry

Measured by GC—MS²—SIR³, endogenous ABA⁴ in embryonicaxes of seeds of Malus pumila L. cv. Golden Delicious decreased8-fold and cotyledon ABA by only 60%, during 10–50 d ofstratification at 5 ?C, after ABA leaching during an initial24 h soaking. During stratification, the percentage germinationof embryos transferred to 17?C showed a significant linear dependenceon log_e of ABA levels in the axes at transfer. Between 50 and70 d, ABA levels increased markedly in axes and testa both ofstratified seeds and seeds allowed to re-dry at 17 ?C afterinitial soaking. The ability of fully stratified axes with elevatedendogenous ABA to germinate indicated that stratification haddecreased their ABA sensitivity. Changes in cotyledon ABA couldnot account for the promotory effect of cotyledons on germinationduring the first 30 d of stratification. Loss of testa inhibitionof germination during stratification was not linked with changesin testa ABA. Stratification markedly increased the sequestrationin the axes of exogenous ABA supplied via the cotyledons. Changesboth in axis ABA levels and sensitivity were thus correlatedwith dormancy release, but subject to modifying control by thecotyledons and testa not involving ABA. Rehydration of driedseeds affected axis ABA later during storage via mechanismsunconnected with dormancy. Key words: ABA, seed dormancy, stratification     

Orientation of gramicidin A transmembrane channel. Infrared dichroism study of gramicidin in vesicles.

Polarized infrared spectroscopy has been used to investigate the orientation of gramicidin A incorporated in dimyristoylphosphatidylcholine liposomes. Dichroism measurements of the major lipid (C = O ester, PO2-, CH2) and peptide (amide A, I, II) bands were performed on liposomes (with or without gramicidin) oriented by air-drying. The mean orientation of the lipid groups and of the pi LD helix chain in the gramicidin has been determined. It can be inferred from infrared frequencies of gramicidin that the dominant conformation of the peptide in liposomes cannot be identified to the antiparallel double-helical dimer found in organic solution. No shift in lipid frequencies was observed upon incorporation of gramicidin in the liposomes. However, a slight reorganization of the lipid hydrocarbon chains which become oriented more closely to the normal to the bilayer is evidenced by a change in the dichroism of the CH2 vibrations. The infrared dichroism results of gramicidin imply a perpendicular orientation of the gramicidin transmembrane channel with the pi LD helix axis at less than 15 degrees with respect to the normal to the bilayer.     

The occurrence ofFusarium andAlternaria on faba bean seed

The studies on the occurrence ofFusarium andAlternaria in faba bean seed have been conducted for three years. The fungal flora in seed lots from healthy plant and from plant inoculated withAscochyta fabae were determined. In addition the occurrence ofFusarium andAlternaria in three parts of seed: testa, cotyledones, and embryo axis were investigated. It was found thatFusarium andAlternaria were present in faba bean seed, but the frequency of occurrence varied depending upon cultivar and experimental year.     

离体发育和萌发中花生种子不同部份内源ABA含量的变化

离体发育和萌发中花生种子不同部份的内源ＡＢＡ含量变化存在明显的差异．种皮和子叶内存在ＡＢＡ的Ｃ（４０）生物合成途径,胚轴内恻为Ｃ（１５）生物合成途径．种子内源ＡＢＡ含量变化和种子活力有密切关系．     

Light-Sensitivity of Hazel Seeds with Respect to the Breaking of Dormancy

Light breaks the dormancy of hazel (Corylus avellana L.) seedswhen the testa is removed. Light, acting via phytochrome, alsopromotes the germination of hazel seeds when the embryonic axisis surgically uncovered. In such seeds with the axis uncoveredremoval of the testa is antagonistic to the light promotionof germination. (Received January 17, 1982; Accepted April 25, 1983)     

Variability in Prosopis farcata in Israel: anatomical features of the seed

Anatomical features of seeds of Prosopis farcata (Banks & Solander) Eig, collected at nine localities from various geographical regions and habitats in Israel, were studied. The seeds differ in size, shape and colour, and also in the cracking ability of the surface layer and whether the palisade layer peels off from the rest of the testa upon imbibition or not.
The gum extruded during imbibition is formed in gum cavities extending from the endosperm throughout the testa up to the palisades.
Water penetration is apparently barred by the outermost wall layers of the external cells of the testa (palisade caps).     

Nutrient resupplementation arrests bio-oil accumulation in Phaeodactylum tricornutum

Phaeodactylum tricornutum is a marine diatom in the class Bacillariophyceae and is important ecologically and industrially with regards to ocean primary production and lipid accumulation for biofuel production, respectively. Triacylglyceride (TAG) accumulation has been reported in P. tricornutum under different nutrient stresses, and our results show that lipid accumulation can occur with nitrate or phosphate depletion. However, greater lipid accumulation was observed when both nutrients were depleted as observed using a Nile Red assay and fatty acid methyl ester (FAME) profiles. Nitrate depletion had a greater effect on lipid accumulation than phosphate depletion. Lipid accumulation in P. tricornutum was arrested upon resupplementation with the depleted nutrient. Cells depleted of nitrogen showed a distinct shift from a lipid accumulation mode to cellular growth post-resupplementation with nitrate, as observed through increased cell numbers and consumption of accumulated lipid. Phosphate depletion caused lipid accumulation that was arrested upon phosphate resupplementation. The cessation of lipid accumulation was followed by lipid consumption without an increase in cell numbers. Cells depleted in both nitrate and phosphate displayed cell growth upon the addition of both nitrate and phosphate and had the largest observed lipid consumption upon resupplementation. These results indicate that phosphate resupplementation can shut down lipid accumulation but does not cause cells to shift into cellular growth, unlike nitrate resupplementation. These data suggest that nutrient resupplementation will arrest lipid accumulation and that switching between cellular growth and lipid accumulation can be regulated upon the availability of nitrogen and phosphorus.     

栝楼属种皮的扫描电镜观察及其分类学意义

栝楼属３１种和３变种皮的扫描电镜观察和比较显示了种皮表面特征的高度多样性,它们可分为长方网型,波浪型,蜂窝型和不规则型等,这些类型的划分能为方子组,柔毛亚组的建立及一些种的归属提供依据。     

Testa and seed appendage morphology in Aeschynanthus (Gesneriaceae): phytogeographical patterns and taxonomic implications

The current sectional classification of the genus Aeschynanthus Jack, essentially based on seed morphology, presents some problems of species placement. A comparative SEM survey of seed and seed appendages was undertaken in order to assess the value of this classification. Seeds of 99 taxa (that is about two‐thirds of the estimated total) were examined and found to fall into two types, A and B. Type A has spiral testa cell orientation, papillae formed from a single cell and short smooth appendages. Type B is recognized by the straight orientation of the testa cells, combined with the presence of papillae formed from the raised ends of two adjacent cells on the long hair‐like appendages and usually on the testa. Only six of the investigated species did not fall into either category. Three have straight testa cell orientation combined with single‐cell papillae and short smooth appendages; the papillae and appendage characters place them in type A. Three have spiral testa cell orientation and short smooth appendages but the testa cells have slightly raised ends; these are also placed in Type A. The three subtypes in Type A are equivalent to the sections Haplotrichium s.s., Microtrichium and Aeschynanthus, but the divisions are less clear than those within Type B. However, other morphological characters support sectional separation. Type B subdivides into three: two subtypes equivalent to sections Polytrichium and Diplotrichium, and a third encompassing section Xanthanthos together with part of the current sect. Haplotrichium, and here referred to as sect. X. There is sufficient morphological correlation with seed type to make the sectional position of many species clear without recourse to seed, particularly in sects Polytrichium, Diplotrichium, Haplotrichium S.S. and Aeschynanthus. There is strong correlation between seed type and geographical distribution. Sects. Microtrichium and Aeschynanthus, with Type A seed, are essentially Malesian. Groups with Type B seed are largely confined to mainland south and south‐east Asia, except for sect. Polytrichium which is more widespread, possibly due to the greater effectiveness of a coma of hairs in wind dispersal. It is suggested that Type A seed, probably sect. Microtrichium, is the least determined and Type B sect. Polytrichium the most derived seed type. Based on these findings a revised key to the sections is provided.     

Electrical stability of artificial membranes

The electrical breakdown potential of the planar lipid membranes has been shown to decrease following UV-induced lipid peroxidation, action of phospholipase A2, adsorption of protamine sulphate and expansion of the membrane by hydrostatic pressure. Membrane potential generated upon the addition of potassium acetate (or ammonium sulphate) and protonophore CCCP to liposomes, when large enough, was also able to break membranes; this was suggested by liposome swelling and a rapid decrease in suspension turbidity. UV-irradiation decreased liposomal membrane breakdown potential, while cholesterol increased it. Detergents and water-soluble products of lipid peroxidation decreased the breakdown potential. The possible role of the membrane electrical breakdown phenomenon in cell pathology is discussed.     

EMBRYO STRUCTURE AND STORAGE RESERVE HISTOCHEMISTRY IN THE PALM WASHINGTONIA FILIFERA

The seed of Washingtonia filifera (Lindl.) Wendl. is hemispherical and has a smooth testa. The embryo is located on the rounded side of the seed near the raphe. The embryo consists of a prominent single cotyledon, an epicotyl, and a small root apex. The shoot apex is oriented at a right angle to the long axis of the embryo and possesses 2 to 3 leaf primordia. The cotyledon functions as a storage organ and is composed of three cell types with similar ultrastructure. These three types—the parenchyma, protoderm, and procambium—can be distinguished on the basis of position, size, and shape. The procambial strands in the cotyledon consist of a ring of bundles grouped into two distinct sympodia and extend from beneath the shoot apical meristem to the tip of the cotyledon where they are situated very close to the surface. The most prominent organelles within all cell types are protein bodies, lipid bodies, and crystalline protein fibers. The protein bodies contain small crystalline inclusions which are presumed to be phytin. Protein bodies in the protoderm were smaller, denser-staining, and contained fewer crystalline inclusions than those in the parenchyma or procambium. On a volume basis, the parenchyma was shown to be 43% protein bodies, 25% lipid bodies, 15% cytoplasm, 7% cell wall, 4% intercellular space, 2% nuclei, and 4% other organelles (mitochondria and plastids).     

Histolocalisation of the oil and pigments in the pumpkin seed

Pumpkin seed oil has a distinct taste and a characteristic green‐red colour. A green layer (chlorenchyma) can be observed in the cross section of the seed on the inner side of the testa. This layer is considered to be a source of protochlorophyll pigment that gives colour to the pumpkin seed oil. However, the histolocalisation of the pigment by selective method was not yet studied. In this study, we localised the oil to the small lipid droplets in the cotyledon cells by Rhodamine 6G lipophilic stain. Furthermore, we localised protochlorophyll to chlorenchyma by microscopic fluorimetry. Emission maximum of protochlorophyll was 700 nm when measured in the seed, but it shifted to 630 and 655 nm (two peaks) when measured in pumpkin seed oil or in the extract.     

Mitochondrial function, content and ROS production in rat skeletal muscle: effect of high-fat feeding

A high intake of dietary fat has been suggested to diminish mitochondrial functioning in skeletal muscle, possibly attributing to muscular fat accumulation. Here we show however, that an 8-week high-fat dietary intervention did not affect intrinsic functioning of rat skeletal muscle mitochondria assessed by respirometry, neither on a carbohydrate- nor on a lipid-substrate. Interestingly, PPARGC1A protein increased by approximately 2-fold upon high-fat feeding and we observed inconsistent results on different markers of mitochondrial density. Mitochondrial ROS production, assessed by electron spin resonance spectroscopy remained unaffected. Intramyocellular lipid levels increased significantly illustrating that a reduced innate mitochondrial function is not a prerequisite for intra-muscular fat accumulation.     

Cholesterol accumulation in Niemann Pick type C (NPC) model cells causes a shift in APP localization to lipid rafts

It has been suggested that cholesterol may modulate amyloid-β (Aβ) formation, a causative factor of Alzheimer’s disease (AD), by regulating distribution of the three key proteins in the pathogenesis of AD (β-amyloid precursor protein (APP), β-secretase (BACE1) and/or presenilin 1 (PS1)) within lipid rafts. In this work we tested whether cholesterol accumulation upon NPC1 dysfunction, which causes Niemann Pick type C disease (NPC), causes increased partitioning of APP into lipid rafts leading to increased CTF/Aβ formation in these cholesterol-rich membrane microdomains. To test this we used CHO NPC1^−/− cells (NPC cells) and parental CHOwt cells. By sucrose density gradient centrifugation we observed a shift in fl-APP/CTF compartmentalization into lipid raft fractions upon cholesterol accumulation in NPC vs. wt cells. Furthermore, γ-secretase inhibitor treatment significantly increased fl-APP/CTF distribution in raft fractions in NPC vs. wt cells, suggesting that upon cholesterol accumulation in NPC1-null cells increased formation of APP-CTF and its increased processing towards Aβ occurs in lipid rafts. Our results support that cholesterol overload, such as in NPC disease, leads to increased partitioning of APP/CTF into lipid rafts resulting in increased amyloidogenic processing of APP in these cholesterol-rich membranes. This work adds to the mechanism of the cholesterol-effect on APP processing and the pathogenesis of Alzheimer’s disease and supports the role of lipid rafts in these processes.