Cell Separation and Anatomy of Abscission in the Oil Palm, Elaeis guineensis Jacq.

Shedding of the fruit of the oil palm takes place in two co-ordinatedstages. The first, a cell separation event at a pre-defined,positionally differentiated abscission zone at the base of thefruit, is followed by further cell separation in peripheraltissue at the junction with the rudimentary androecial ringand the tepals. The position of the second separation is determinedby the age and ripeness of the fruit and the degree of pressureto which it is subjected; it is also dependent upon completionof the first stage. Implications of this unusual two stage separationprocess are discussed. Key words: Abscission, cell separation, anatomy, oil palm, Elaeis guineensis     

Fat Metabolism in the West African Oil Palm (Elaeis guineensis)

During germination in the light, the endosperm, containing ahigh proportion of reserve fat (composed largely of shorter-chain(C₈ to C₁₄ saturated fatty acids), is slowly invaded by theexpanding haustorium (cotyledon). Free fatty acids accumulatein the endosperm, preferential hydrolysis of longer-chain saturatedacids (C₁₄ to C₁₈ occurring under conditions of slow growth.Lipids are absorbed by the haustorium, the process being superficiallysimilar in certain respects to intestinal fat absorption. Whencomplicating factors are removed, absorption is found to beunselective during disappearance of 75 per cent, of the endospermlipids. Amounts of lipid in the haustorium are low compared with thehigh concentration in the surrounding endosperm and, beforephotosynthesis starts, losses through respiration account fora large part of the reserves which disappear. No free fattyacids are present in the haustorium. Breakdown of fatty acids is relatively unspecific, althoughthe acids characteristic of the haustorium (C₁₆ C₁₈, oleic andlinoleic acids) are metabolized some what less rapidly thanthe shorter-chain saturated acids (C₈ to C₁₄ characteristicof the endosperm fat. Both root and shoot have a low fat content. The fatty-acid compositionof the former changes little during growth, but in the shootlinolenic acid increases proportionately during leaf expansionin the light.     

Chilling-induced Lipid Hydrolysis in the Oil Palm (Elaeis guineensis) Mesocarp

Oil palm fruits exposed to temperatures of 15 °C and belowshowed a significant increase in free fatty acid (FFA) contentin the mesocarp. This effect was most pronounced in fruits exposedto 5 °C when FFA levels exceeding 70% of the total oil wereobserved. The increase in FFA was accompanied by an increasein lipid-soluble phosphorus levels and a decrease in carotenecontent. Chilling did not have an effect on palm kernel oil.The results suggest the activation of a lipase in the mesocarpby low temperature stress. Key words: Lipase, oil palm, free fatty acid     

The Distribution and Mobility of Boron within the Oil Palm, Elaeis guineensis L.: I. Natural Distribution

Leaf boron concentration is important in determining applicationof this element in oil-palm plantations. Older leaves of oilpalm contain more boron than younger leaves while tips and marginsof leaflets contain the highest levels of boron. Upper rankleaflets contain more boron than lower rank leaflets and upward-pointingleaflets contain more boron than downward-pointing leaflets.Boron concentration in leaves varies diurnally, and also overlonger periods; boron accumulates with time but at times ispunctuated with loss of boron. The significance of these observationsis discussed.     

Identification of p.Methoxyallybenzene in the Pollen of the Oil Palm Elaeis guineensis Jacq.

The lipid extract prepared from the pollen of the West African,oil palm, Elaeis guineensis, was found to contain p-methoxyallylbenzenein substantial amount. The pure substance after isolation bymeans of preparative gas-liquid chromatography and steam distillationwas characterized by using a combination of g.l.c.-mass spectrometry,infrared spectrometry, and chemical reactions. Mass spectrometrygave a spectrum with a parent ion at m/e 148 corresponding tothe molecular weight and fragmentation ions at m/e 133, 121,117, 105, 91, and 77. The structure was further confirmed bymeans of the infrared spectrum which showed major peaks at 1250,920, and 815 cm^–1 corresponding to a CH₃O group, a 1,4-substitutedaromatic ring, and a RCH=CH₂ group respectively. Its chemicaland physical properties (hydrogenation, oxidation, etc.) werefound to be similar to those of its positional isomer, p-methoxy--phenylpropene.The physiological and economic importance of the compound arediscussed.     

Some Enzymic Activities in the Germinating Oil Palm (Elaeis guineensis) Seedling

In germinating oil palm (Elaeis guineensis var D × P) seedling, an active lipase was present in the shoot but absent from both the kernel and the haustorium. It has an optimum pH of 6.2 and a smaller peak at pH 8.6. The shoot lipase was active against a number of mono-, di-, and triacylglycerols as well as the endogenous lipids present in the shoot, haustorium, and kernel. Activity against related substrates were in the order: trilaurin > dilaurin > monolaurin but monopalmitin > dipalmitin > tripalmitin. The level of the enzyme in the seedling was highest at a relatively early stage of growth (18-21 days) and also higher in dark-grown seedlings. Glyoxylate bypass enzymes (malate synthetase and isocitrate lyase), glutamate-oxaloacetate transaminase, phosphoenolpyruvate carboxykinase and lauroyl-coenzyme A oxidase were located in the haustorium. The levels of the enzymes paralleled seedling development and were slightly higher in light-grown seedlings. Fatty acyl-coenzyme A synthetase activity was very low and was found in both the shoot and haustorium.     

Origin of Initial Microflora of Palm Wine from Oil Palm Trees (Elaeis guineensis)

S ummary . In a study of the origin of the initial microflora of palm wine from the oil palm ( Elaeis guineensis ), micro-organisms from parts of the immature spadix, the plant tissues around the point of tapping the tree, the palm leaves and the atmosphere around the palm trees, were isolated and examined. It was shown that the yeasts in fresh palm wine might have originated from those that colonize those parts of the palm which are covered with fluffy hairy outgrowths. These materials which surround the tapping hole are the stalk of the male inflorescence, the leaf petiole, the felt (a fabric-like outgrowth of the frond petiole used to cover the tapping hole) and the cross strips. Another possible source of the yeasts was the xylem stream.     

Histology of Somatic Embryogenesis from Leaf Explants of the Oil Palm Elaeis guineensis

Histological analysis was carried out during the sequence ofevents which lead to the obtaining of somatic embryos of oilpalm. Calluses from the division of perivascular cells formedat the veins of young leaf explants. Subsequent proliferationof histologically similar nodules was by means of a cambium-likezone. Under certain conditions these calluses consisted almostentirely of meristematic cells. They then differentiated rapidly:the cambium-like zone fragmented, leading to protuberance inwhich the cells divide rapidly; epidermal structures were formed,with a network of procambial strands, and synthesis of storagelipids accompanied the formation of these embryo-like structureswhich developed into clumps of true somatic embryos, each witha shoot apex and a root apex. Other structures frequently observedduring in vitro culture are also described and show that alternatepathways do exist. The structure and evolution of somatic embryosare compared to those of zygotic embryos. Storage lipids emergeas an early tracer of the satisfactory development of tissuetowards somatic embryogenesis. Oil palm, Elaeis guineensis, histology, somatic embryogenesis, callogenesis, storage lipids     

The Distribution and Mobility of Boron Within the Oil Palm, Elaeis guineensis L.: II. The Fate of Applied Boron

The distribution of boron following application of the elementto the palm was studied. Results indicate that boron moves inone direction from the roots to the leaflet and from the leafletssome boron can be lost by guttation. The practical implicationsof the results with regard to methods of boron application anduse of leaf analysis as a diagnostic tool are discussed.     

High-temperature Pre-treatment and the Germination of Seed of the Oil Palm, Elaeis guineensis (Jacq.)

Germination experiments have shown that oil palm seeds requireheattreatment before they germinate. The heat-treatment is insome ways analogous to low-temperature stratification of temperateseed, as it may be applied as a pretreatment, even at a moisturecontent too low for germination to occur. Following the heatpre-treatment, seed brought to the optimum moisture contentgerminates rapidly, after an initial lag period, at ambienttemperature. Below a critical seed moisture content, heat-treatmentis ineffective although seed viability is largely unimpaired.The high-temperature reaction has a Q₁₀ between 3.5 and 5.0and is apparently irreversible. Heat-treatment may be effectivelyapplied to stored, as well as fresh, seed. A reinvestigationof the optimum temperature for the high-temperature reactionshowed that dry heat-treatment is effective at 42.0°C.,the duration of the treatment necessary being only 60 days comparedwith the previously accepted value of 80 days at 39.5°C.necessary for seed heat-treated at optimum moisture content.A temperature of 44.5°C. is rapidly fatal. These resultsare discussed in relation to the alternation of dry and wetseasons in West Africa, and in relation to practical aspectsof oil palm cultivation.     

Composition, Degradation and Utilization of Endosperm During Germination in the Oil Palm (Elaeis guineensis Jacq.)

The insoluble carbohydrate and lipid fractions, and -D-galactosidase,ß-D-mannosidase and isocitrate lyase activities werestudied in the various tissues of oil palm (Elaeis guineensisJacq.) kernels prior to and during germination. In ungerminatedkernels insoluble carbohydrate and lipid constituted 36 and47% of endosperm dry weight respectively. During germinationthe thick endosperm cell walls became markedly thinner, concurrentwith a significant decrease in the percentage of insoluble carbohydrateand an increase in -galactosidase and ß-mannosidaseactivity in both degraded and residual endosperm. The proportionof lipid in degraded endosperm also increased significantly.The insoluble carbohydrate appears to be a galactomannan locatedin the secondary walls of the endosperm. No galactomannan wasdetected in oil palm embryos or haustoria. Isocitrate lyasewas present in, and confined to, tissues of the haustorium ofgerminating kernels. The enzyme was not active in endospermat any stage of germination, nor was it active in embryos beforeor at the end of imbibition. The results suggest that galactomannan is the second largestcomponent of oil palm endosperm and that it is utilized morerapidly than lipid during the early stages of germination. Thefact that isocitrate lyase activity is confined to the haustoriumsuggests that in Elaeis gluconeogenesis, the conversion of triglycerideto carbohydrate, takes place entirely within the cotyledon ofthe seed. Elaeis guineensis, galactomannan, galactosidase, germination, isocitrate lyase, mannosidase, oil palm     

Lipid Composition and the Role of the Haustorium in the Young Seedling of the West African Oil Palm, Elaeis guineensis Jacq.

The lipid and fatty acid composition of the haustorium of thedeveloping seedling of the West African oil palm, Elaeis guineensisJacq. has been studied using the combined techniques of thin-layerand gas-liquid chromatography. In addition to triglycerides,which represented over 75 per cent of the total lipids, therewere present small quantities of free fatty acids, diglyceridesand polar lipids. The two glycolipids, monogalactosyl and digalactosyldiglycerides, formed the bulk of the polar lipids with smallamounts of phosphatidyl choline and phosphatidyl inositol. In general, the fatty acid pattern of the haustorium was intermediatebetween that of the palm kernel oil and the palm fruit mesocarp,and resembled to a great extent the fatty acids of the kerneltesta. It is suggested, from the presence of the biological membranelipids and lipolytic enzymes, that the main function of thehaustorium is that of food mobilization and transport for theyoung plant.     

Prospects for Biotechnology in Oil Palm (Elaeis guineensis) and Coconut (Cocos nucifera) Improvement

Abstract

Research into human metabolism is expanding rapidly due to the emergence of metabolism as a key factor in common diseases. Mathematical modeling of human cellular metabolism has traditionally been performed via kinetic approaches whose applicability for large-scale systems is limited by lack of kinetic constants data. An alternative computational approach bypassing this hurdle called constraint-based modeling (CBM) serves to analyze the function of large-scale metabolic networks by solely relying on simple physical-chemical constraints. However, while extensive research has been performed on constraint-based modeling of microbial metabolism, large-scale modeling of human metabolism is still in its infancy. Utilizing constraint-based modeling to model human cellular metabolism is significantly more complicated than modeling microbial metabolism as in multi-cellular organisms the metabolic behavior varies across cell-types and tissues. It is further complicated due to lack of data on cell type- and tissue-specific metabolite uptake from the surrounding microenvironments and tissue-specific metabolic objective functions. To overcome these problems, several studies suggested CBM methods that integrate metabolic networks with gene expression data that is easily measurable under various conditions. This specific objective functions are expected to improve the prediction accuracy of the presented methods. Such objective functions may be derived based on computational learning that would give optimal correspondence between predicted and measured metabolic phenotypes (Burgard, 2003).

The CBM methods presented here open the way for future computational investigations of metabolic disorders given the relevant expression data. A first attempt to visualize and interpret changes in gene expression data measured following gastric bypass surgery via a genome-scale metabolic network was done by Duarte et al (Duarte, 2007). Another potential application would be the prediction of diagnostic biomarkers for metabolic diseases that could be identified via biofluid metabolomics (Kell, 2007). Towards this goal, we have recently developed a CBM method for predicting metabolic biomarkers for in-born errors of metabolism by searching for changes in metabolite uptake and secretion rate due to genetic alterations (Shlomi, 2009). Incorporating cell type- and tissue-specific gene expression data within this framework can potentially improve the identification of diagnostic biomarkers. Overall, the methods presented here lay the foundation for studying normal and abnormal human cellular metabolism in tissue-specific manner based on commonly measured gene expression data.     

An Analysis of the Factors Controlling the Germination of the Seed of the Oil Palm, Elaeis guineensis (Jacq.)

Under natural conditions in West Africa at the average groundtemperatures of 25-30° C, oil-palm seed germinates sporadicallyover a period of years, but with continuous heat treatment (38-40°C.) 50 per cent, germination of either nuts or extracted kernelsoccurs within a few months. The kernel comprises a small cylindrical embryo embedded ina mass of oily endosperm which in turn is surrounded by a thicktesta. At germination the testa and layer of endosperm coveringthe distal part of the embryo are forced out as a disc-likeoperculum which is already demarcated in the ungerminated kernelby a circular abscission zone in the endosperm cells. The excised embryo is non-dormant and at 30° C. starts toelongate within 24 hours, either on moist filter paper or whilestill in contact with the endosperm. At 30° C. removal of the operculum is followed by sluggishemergence of the embryo in air; emergence at the normal rateoccurs in pure oxygen, or in air if a long period at high temperatureprecedes de-operculation. Fresh intact kernels remain ungerminatedfor at least 6 months at 30° C, either in air or in pureoxygen. At high temperature (40° C.) intact kernels germinate fasterin pure oxygen than in air; at 30° C. the same applies onlyafter previous treatment at high temperature. This acceleratingeffect of oxygen is shown to be dependent upon the progressof slow processes stimulated by high temperature. It is postulated that germination of oil-palm seed is dependentupon a minimal threshold concentration of oxygen in the embryoand that during dormancy this minimal level progressively decreasesat a rate depending on the temperature.     

Oil Palm (Elaeis guineensis Jacq.) Clonal Fidelity: Endogenous Cytokinins and Indoleacetic Acid in Embryogenic CallusCultures

Endogenous levels of indole-3-acetic acid (I AA) and cytokininswere measured in the two types of callus of oil palm (ElaeisguineensisJacq.) by an HPLC-ELISA methodology. The Nodular Compact Callus(NCC) is commonly used to establish stableembryoid strains ensuringclonal fidelity(     

Sex Differentiation in Oil Palm: Effects of Growth Regulators

Gibberellic acid is shown to increase the production of maleinflorescences, and reduce production of females, in the oilpalm, Elaeis guineensis Jacq. Ethephon and -naphthyleneaceticacid also have effects on sex ratio, but it is suggested thatthese may be indirect effects, in contrast to that of gibberefficacid which is considered to be a direct effect on the processof sex differentiation. 2-Chioroethyl trimethylammonium chloridehad no effect on sex ratio.     

Cytokinin Differences in In Vitro Cultures and Inflorescences from Normal and Mantled Oil Palm (Elaeis guineensis Jacq.)

The mantled abnormality phenotype of the oil palm affects fruit development and thus jeopardizes oil yield. Cytokinins have been implicated in the development of the mantled phenotype. Endogenous cytokinin levels in the normal and mantled phenotypes were compared to determine whether levels of specific cytokinins are associated with mantling. Endogenous cytokinins were identified and quantified in in vitro cultures and inflorescences from normal and mantled oil palms. Twenty-two isoprenoid cytokinins, comprising the zeatin, dihydrozeatin, and isopentenyladenine types, were quantified. Total cytokinin levels, particularly of trans-zeatin and isopentenyladenine types, increased during the in vitro culture process, with the highest levels detected at the proliferating polyembryoid stages. The cytokinins were present mainly in their inactive 9-glucoside forms during in vitro culture. On the other hand, the predominant trans-zeatin cytokinins in inflorescences were present mainly in their ribotide forms, suggesting a metabolic pool of cytokinins for conversion to biologically active free bases or ribosides. Levels of specific cytokinins were significantly different in tissues at different stages. Mantled developed inflorescences contained higher levels of isopentenyladenine 9-glucoside compared with normal inflorescences. Mantled-derived callus tissues had higher isopentenyladenine levels but significantly lower levels of trans-zeatin 9-glucoside, dihydrozeatin riboside, and dihydrozeatin riboside 5′-monophosphate cytokinins compared with normal-derived callus. It would be of considerable interest to verify these specific cytokinin differences in more callus cultures and clones.     

Fat Metabolism in the West 4frican Oil Palm (Elaeis guineensis): PART III. FATTY ACID FORMATION IN THE MATURING EXOCARP

Accumulation of fat in the oil-palm exocarp is delayed untilthe kernel has almost finished developing (at about 19 weeksafter pollination) and is then extremely rapid, a major partof the lipid being formed within a single week. Throughout theperiod studied (8 to 20 weeks after pollination) the fat-freedry weight remains approximately constant and carbohydrates(starch, sucrose, and reducing sugars) do not accumulate eitherprior to or during fat formation. Immature exocarps contain only a low proportion of fat (about1 per cent, of the dry weight) and this ‘protoplasmic’lipid has a different fatty acid composition (major componentspalmitic and linoleic acids accompanied by smaller amounts ofstearic and linolenic acids) from the later-formed oil (majorcomponents palmitic and oleic acids with smaller amounts ofstearic and linoleic acids). There is no evidence of fatty acidinterconversions at any stage of development.     

Fruit Ripening in the Oil-palm Elaeis guineensis

Some gross morphological, biochemical, and quantitative sizechanges of the fruit which occur during the 150 or 80 days fromfertilization to ripeness for this species are described. Threemain phases of development are discernible. For the first 15days little activity may be noted. This is followed by a differentiationperiod of 60 to 70 days during which the fruit develops to almostmaximum size and the embryo, endosperm, mesocarp, and epicarpare virtually completely differentiated. The last period ofripening is considered a maturation period during which timethe embryo becomes viable, the tissues become consolidated intofinal forms, and oil formation in the endosperm and mesocarptakes place. These processes are described quantitatively withgrowth curves.     

Metabolism of Cytokinins by Tissue Culture Lines of Oil Palm (Elaeis guineensis Jacq.) Producing Normal and Abnormal Flowering Palms

The metabolism of cytokinins in tissue cultures of two oil palm clones previously known to regenerate palms ultimately manifesting normal and abnormal flowering was studied using radiolabeled benzyladenine and isopentenyladenosine, with particular regard to the kinetics of formation of the cytokinin 9-glucoside. Labeled products were separated by high performance liquid chromatography and identified by comparison of retention times with authentic cytokinin standards run immediately before or after the experimental sample. Using benzyladenine, which is insensitive to cytokinin oxidase, ribotide appeared rapidly and then declined. 6-Benzylaminopurine (BA) 9-glucoside quickly became the major soluble product with some formation of riboside. No other ethanol-soluble products were found. Over an incubation period of 24 h up to 30% of label appeared in the ethanol-insoluble fraction. The uptake of label was consistently faster in the normal than the abnormal clone. Dose-rate and time course experiments produced an in vivo asymptotic dose-response curve for the accumulation of BA 9-glucoside analogous to a Michaelis-Menten first-order reaction with a ~~``V <sub>max</sub>' of 3.5 nmol·g<sup>−1</sup>·h<sup>−1</sup> (on a fresh weight basis) and a ``K _m ' of 0.12 mm. There were no differences between clones in the rate of synthesis. Using isopentenyladenosine, which is susceptible to cytokinin oxidase and cannot be glucosylated without prior deribosylation, a complex pattern of metabolism was seen, with much slower production of 9-glucoside. A number of transient unidentified compounds were seen, together with adenosine and adenine. Comparison of normal and abnormal flowering clones showed striking differences in the kinetics of production of a compound thought to be [9R]Z and in a transient compound eluting at 22 min which accounted for 42% of the radioactivity after a 7-h incubation in the abnormal line. By 17 h there was no difference between normal and abnormal lines in the radioactivity in this compound. Cytokinin uptake was slower in the abnormal than in the normal flowering clone. Received December 17, 1997; accepted August 24, 1998