Solid Endosperm Research Articles

Study on Fatty Acid Composition and Amino Acid Content of Coconut Endosperm of Selected Coconut Cultivars in Thailand

The nutritive values of tropical fruits like coconut are of interest to consumers and useful for the breeding program. The two experiments were carried out in Completely Randomized Design with 3 replications. The first experiment aimed to determine the essential and non-essential amino acid content of liquid and solid endosperm of potential market varieties of coconut such as young tender nut of Aromatic Green Dwarf (Nam Hom) and mature nut of hybrid Nam Hom x Kathi (NHK). Among the 18 kinds of amino acids, the significant differences were found on Aspatic acid, Cystine, Serine, Isoleucine, and Phenylalanine content while highly significant differences were found on Histidine and Methionine content. The second experiment aimed to determine the fatty acid composition of virgin coconut oil of 20 coconut accessions from the coconut field gene bank of Thailand at Chumphon Horticultural Research Centre. The result showed that there were significant differences on the eight fatty acid compositions. Among the eight fatty acids, lauric acid is the most noted one by consumers and it was found that lauric acid content in virgin coconut oil (VCO) was excellent (lauric acid > 48.8%) and the mean of lauric aicd content among the eight varieties had no significant difference at 5% level by DMRT. These varieties include including Renell Tall, Chumphon Hybrid No. 2, Malayan Yellow Dwarf, Sawi Hybrid No.1 (MAWA), Hybrid Chumphon 60, Thai Red Dwarf, Sri Lanka Tall, and Hybrid Nam Hom x Kathi (NHK) with the lauric acid content at 51.0, 50.1, 49.3, 49.0, 49.0, 49.0, 48.9, and 48.8%, respectively. These varieties, therefore, were suitable for VCO processing since they have high lauric content.

EFFECT OF PHYSIOLOGICAL AGE AND GROWTH REGULATORS ON CALLUS BROWNING OF COCONUT ENDOSPERM CULTURE IN VITRO

The possibility of physiological age and growth regulators affecting callus browning of coconut endosperm was investigated. Solid endosperm explants of four coconut fruits from same brunches of two coconut cultivars “Samoan Dwarf” were grown on modified Murashige and Skoog (MS) formula with addition of 10 mg l-1 putresine, 2.50 g l-1 activated charcoal (AC), 1.70 g l-1 phytagel, 0, 10-6, 10-5, 10-4, 10-3 M 2,4-dichlorophenoxyacetic acid (2,4-D) or 4-amino-3,5,6-trichloropicolinic acid (Picloram)  combined with 10-5M 6-benzylaminopurine (BA). Callogenesis occurred on 98.83% of explants.  Callus browning between different physiological ages (antipodal and micropylar tissues) of coconut endosperm at  9, 26 and 31 weeks of culture (WOC) was significantly different, but not at 16 and 21 WOC. Auxins of 2,4-D and Picloram did not affect significantly callus browning of endosperm cultures. Auxin doses at 10-6, 10-5, and 10-4M decreased significantly callus browning at 9 and 16 WOC, respectively,  but at 10-6M  browning was less significant compared to  other doses at  21 WOC. Auxin dose at 10-3 M caused  less significant  browning compared to  other doses at  31 WOC. The addition of BA decreased significantly callus browning at  9 WOC , but did not affect callus browning thereafter. Key words: Coconut, in vitro, Picloram, 2,4-D, BA Â

Differentially expressed microRNAs during solid endosperm development in coconut ( Cocos nucifera L.)

MicroRNAs (miRNAs) are a class of 20–24 nt, endogenously expressed, non-coding RNAs that play important regulatory roles in plants and animals. To identify miRNAs potentially involved in tissue development and compound anabolism, we studied miRNA expression profiles in endosperm of coconut at different developmental stages. Based on the annotation in miRBase (release 10.1), we measured a total of 179 miRNAs in immature (95 expressed miRNAs) and mature tissues (176 expressed miRNAs) using microarrays, respectively. The comparative analyses on miRNA expression profiles between these two groups of tissues showed that 23 miRNAs were up-regulated and nine miRNAs were down-regulated in matured endosperm. We further confirmed the increased expression of four miRNAs and decreased expression of a miRNA in immature endosperm using real-time PCR. Moreover, we computationally predicted the target genes of 32 miRNAs with differential expression ( p < 0.01), and identified the lowest-score targets of six miRNAs. Finally, we discussed the potential functional relevance of several differentially expressed miRNAs.

SEASONAL VARIATIONS IN FATTY ACID COMPOSITION OF OIL IN DEVELOPING COCONUT

ABSTRACT Studies on seasonal variation in oil and fatty acid profile of developing solid endosperm of two cultivars, West Coast Tall (WCT) and Chowghat Orange Dwarf (COD), and their hybrids indicated that oil percentage increased from 30% in 6‐month‐old nuts to 63% in matured nuts (12 months old). Nuts sampled during July from different levels of maturity had high oil percentage and followed by those sampled during April, October and January. During nut development to maturity, the percentages and contents of medium and long chain saturated fatty acids increased except that of palmitic and myristic acids. Concentration of long chain unsaturated fatty acids (LCUFAs) in developing coconut kernel were high at 5 and 6 months after fertilization and then decreased toward maturity. The LCUFAs were high in nuts developing during October; consequently, saturated to unsaturated fatty acid ratios were low during October. Results indicated that nuts matured during October had better nutritional quality for human consumption and those matured during January are more suitable for industrial purpose due to higher medium chain fatty acid concentrations. PRACTICAL APPLICATIONSCoconut is consumed either as the tender nut (5–6 months after fertilization) or as the kernel from mature nut (12 months after fertilization). Recent technologies of making snowball tender nut use the nuts aged 7–8 months old. Kernel also is consumed in this product. Apart from this, the coconut is being increasingly used for making different kernel‐based value‐added products. This information is useful, as the value‐added products are being developed using different maturities of coconut. Hence, it is of paramount importance that the fatty acid profile of coconut kernel is known in detail for assessing the safety of food consumption from the human health point of view. Apart from this, information on the seasonal variation in fatty acid profile of developing endosperm gives an integrated knowledge so as to optimize the usage of coconut kernel for both human consumption and industrial exploitation.

Conservation value of an exotic species: the case of coconuts on the Kayapo indigenous lands, south-eastern Amazonia

In a meeting between FUNAI (the Brazilian Indian National Foundation) and the Kayapo in the Kayapo village of Aukre, in October 2005, the Kayapo Indians requested support to increase the culture of coconuts (Cocos nucifera) in their lands. The introduction of exotic species is a cause of biological diversity loss throughout the world. However, this is by no means applicable to all kinds of exotic species. We argue that the culture of coconuts may actually be a useful tool for the conservation of this country’s indigenous lands, despite criticism to the contrary. It may also be useful as source for raw material for the indigenous people who are presently experiencing a population boom. For the Kayapo of south-eastern Amazonia, such a demographic explosion, coupled with their increasing dependence on money to purchase industrialized goods, tend to substantially increase the pressure on their lands, which still contain a substantial amount of well-preserved seasonally-dry Amazonian forests. We investigated the actual economic relevance of coconuts for the Kayapo by measuring human and coconut populations and found that this exotic palm is not important for the subsistence of these Indians, due to coconut scarcity, and that such importance is not forthcoming. In the Amazon, coconuts may be particularly useful for the Indians’ nutrition due to the high energetic value of the solid endosperm of the mature fruit. Therefore, given the importance of indigenous lands for the conservation of the Amazonian forests, the encouragement of subsistence coconut cultures in indigenous lands is defensible as a measure for the conservation of biodiversity.

Extraction of genomic DNA from the lipid-, polysaccharide-, and polyphenol-rich coconut (Cocos nucifera L.)

One prerequisite to reliable molecular biology work is that the genomic DNA of a sample be of good quality. Coconut is quite difficult to work on because of the high lipid and polysaccharide content of its endosperm and the high polyphenol content of its leaves. This study aimed to determine which protocol to use and which part of the coconut tree is most appropriate to extract good-quality genomic DNA. Genomic DNA from the solid endosperm was found to be of poor quality because of high levels of lipid and galactomannan contaminants. By using a modified protocol by Cheung et al. (1993) as modified by Rogers et al. (1996) and by Dellaporta et al. (1983) as modified by Datta et al. (1997), genomic DNA extracted from the young leaves of the first emergent frond provided enzyme-digestible, good-quality DNA. The modification involved the use of a higher salt concentration (2 M instead of 0.5 M) in the extraction buffer and the use of polyvinylpolypyrrolidone. Moreover, this modified protocol did not involve the use of organic solvents.

Larval competition in weevils Revena rubiginosa (Coleoptera: Curculionidae) preying on seeds of the palm Syagrus romanzoffiana (Arecaceae)

Inter- and intraspecific local resource competition may lead to the selection of specific adaptive individual characteristics to overcome interference competition. A highly selective scenario is predictable for interference competition among seed preying weevil larvae that live in and feed upon a single host seed. This scenario is found in Syagrus romanzoffiana palm seeds which are predated by Revena rubiginosa (Curculionidae) larvae. Although multiple infestation of one seed by weevil larvae can occur, invariably only one individual survives and develops in each host seed. A strong competition between the first instar larvae in a restricted window of host fruit development stages leads to physical interactions of conspecifics by ovicide or direct fighting using falcate mandibles. The occurrence of this type of mandible is synchronized with fruit development and restricted to instars with probable competition, as infestation occurs only while the endocarp is soft. Only after lignification of the endocarp the larva changes into the next instar. Mandibles of subsequent instars differ markedly from those of the first instar. The new mandibles can scrape the solid endosperm but are unable to perforate and kill conspecifics. These findings give strong evidence for the selective pressure of intraspecific competition, where special behaviour, mandible morphology and synchronization of its changes with the seed development contribute to individual benefit that involves the killing of conspecifics, since one host seed can only maintain a single larva throughout its complete development.

Variability in fatty acid and triacylglycerol composition of the oil of coconut (Cocos nucifera L.) hybrids and their parentals.

The fatty acid profiles and triacylglycerol (TAG) compositions of oils from the solid endosperm of different Philippine coconut hybrids and their parentals were determined by using gas chromatography (GC) and high-performance liquid chromatography (HPLC). In general, varietal differences in fatty acid composition were observed. Lauric acid (C12) content was significantly higher in the hybrids PCA 15-8 (50.45%) and PCA 15-9 (50.26%) by about 3.16% points as compared to other hybrids, and higher in Tacunan Green Dwarf (50.50%) among the parentals. Among the fatty acids, lauric acid exhibited the least variation. In general, none of the hybrids had higher fatty acid content than their parentals. The HPLC chromatogram of triacylglycerols (TAG) showed 8 major peaks which differ in carbon number (CN) by two: identified as TAG CN 30, 32, 34, 36, 38, 40, 42, and 44. TAGs CN 30 (4.08%) and CN 34 (19.20%) were found to be significantly higher in PCA 15-9 than in the other hybrids. CN 36 was highest (21.94-23.66%) in all hybrids and parentals. The TAG CNs varied significantly among hybrids and parents, i.e., in CN 30, 32, and 34, which are high in medium chain triacylglycerols (MCTs), and in CN 30 (for parentals only), 40, 42, and 44 (the latter two for parentals only), and none in CN 36. MCTs calculated for two hybrids and their parents ranged from 13.81% to 20.55%.

Changes in fatty acid composition during development of tissues of coconut (Cocos nucifera L.) embryos in the intact nut and in vitro.

Intact coconuts were germinated in situ and compared with excised zygotic embryos germinated in vitro. The growth of the embryonic tissue and their fatty acid compositions were measured. Haustoria, plumules and radicles of coconuts germinated in situ grew continuously and proportionately throughout the 120 d experiment with haustauria increasing to 45 g x nut(-1) and weighing 4-5-fold more than the other two tissues. The plumules and radicles of the seedlings cultured in vitro also grew continuously but the haustoria grew sporadically between 15 d and 75 d in culture and, at 250 mg x nut(-1) after 75 d, were smaller than the other two tissues. All the tissues of the nuts grown in situ contained significant amounts of lauric acid, the acid characteristic of coconut oil, as well as longer chain saturated and unsaturated fatty acids. The content of medium and long chain fatty acids increased in all growing tissues as the experiment proceeded, especially the haustorium which contained 24-35% of its fatty acid as lauric acid; the fat content of solid endosperm reduced during this period. Seedlings grown in vitro, on the other hand, failed to accumulate lauric acid in any of their tissues (haustorium contained 6-11% of its fatty acid as lauric acid). The results may have implications for the design of growth media for growing zygotic and somatic cultures of coconut and may provide a marker for successful germination.

Reliability of the Kernel Milkline Method for Timing Corn Silage Harvest in Ohio

The position of the kernel milkline (ML) has been recommended as a reliable guide for determining the optimal time to harvest corn (Zea mays L.) for silage. This method has not been tested adequately in the central and eastern Corn Belt, and the effect of planting date on variation in whole plant dry matter (DM) content at different ML stages is unknown. The objective of this research was to determine the variation in whole plant DM content at different kernel ML stages of corn grown in Ohio. Three hybrids representing early, mid, and full season maturities for central Ohio were planted on or about 1 May, 21 May, and 10 June 1992 and 1993. Kernel ML stage and whole plant DM content were determined every 3 to 7 d beginning at full dent (FD) stage until ML disappearance. Kernel ML stage and whole plant DM content were positively correlated (r = 0.89). On average, the kernel ML would have been an excellent indicator of when to harvest corn for silage; however, we found considerable variation in plant DM content within a given ML stage for individual sampling dates from all hybrids and environments. Variation in DM content was present regardless of year, planting date, or hybrid. Although corn was more likely to be at an ensilable DM content at certain stages than others, the variation in plant DM content within a stage was sufficient to raise concern over the reliability of the kernel ML method for determining when to harvest a particular field for silage in Ohio. Gravimetric determinations of plant DM content should be used to confirm when corn is at the optimal DM content for ensiling. Corn silage growers in Ohio should begin making gravimetric determinations of plant DM content at FD for conventional tower or bunker silos, and 1/4 ML for sealed (oxygen-limited) tower silos.

Galactomannan degrading enzymes in maturing normal and makapuno and germinating normal coconut endosperm

β-Mannosidase activity in the maturing normal endosperm of coconut decreased from 1.40 milliunit/mg protein at 7–8 months to 0.29 milliunit/mg protein at 11–12 months. It was 6–10 times lower at 7–8 and 8–9 months and was not detected at the more mature stages of makapuno. In contrast, the liquid endosperm from normal nuts increased in α- d-galactosidase, β-mannanase and β-mannosidase activity as development progressed. In makapuno liquid endosperm, the values for all the enzymes were consistently low during endosperm maturation. During germination, α- d-galactosidase activity in the solid endosperm increased from 0.51–0.84 unit/mg protein. β-Mannanase and β-mannosidase activity increased from 33.12 to 67.76 milliunit/mg protein and 5,13 to 43.05 milliunit/mg protein, respectively. In the haustorium, α- d-galactosidase activity remained at 0.25–0.27 unit/mg protein while β-mannanase increased from 55.34 to 138.12 milliunit/mg protein. β-Mannosidase decreased from 371.79 to 165.17 milliunit/mg protein. The implications of enzyme levels of α- d-galactosidase, β- d-mannanase and β- d-mannosidase on the mode of galactomannan degradation in the developing and germinating nut and phenotype determination of both normal and makapuno nuts are discussed.

In vitro growth of embryos and callus of coconut palm.

A medium for optimal growth of embryos of Jamaican Tall and Green Malayan Dwarf varieties of coconut palm was developed. The Liquid basal Murashige and Skoog medium was supplemented with coconut milk, IAA and 2IP. Activated charcoal improved embryo growth on agar medium. A single callus line was initiated from solid endosperm and subcultured on basal Schenk and Hildebrandt medium supplemented with 2 mg per 1 NAA. Attempts at inducing organogenesis in the callus were unsuccessful. No vascular tissue was present. The callus was aneuploid with the chromosome number = 8 (normal 2n = 32).

A cytoembryological study of Agrostis pilosula

A detailed investigation of microsporogenesis, megasporogenesis, female gametophyte development, and embryogeny in Agrostis pilosula Trin. has been made. The chromosome number of 2n = 44 is the first record for this species. Pollen mother cell meiosis reveals normal chromosome behaviour. Microspore tetrads are mostly isobilateral. The bitegmic ovule is initially anatropous and becomes hemianatropous. The inner integument delimits the micropyle. A single archesporial cell, which is hypodermal or, more rarely, deeply seated in origin, directly functions as the megaspore mother cell. Meiosis usually results in the formation of a T-shaped tetrad of megaspores, but occasionally a linear triad of megaspores is seen instead. After three mitotic divisions, the chalazal megaspore gives rise to an eight-nucleate embryo sac. The mature female gametophyte is atypical because of the lateral displacement of antipodals and its triangular shape. It consists of two synergids, a pear-shaped egg slightly pushed aside, fused polar nuclei in close approximation to the egg cell, and three large ballooned laterally displaced coenocytic antipodal cells with hypertrophied nuclei. This antipodal condition might be associated with hormonal imbalance. The endosperm is free nuclear at first and leads to the formation of solid endosperm. Starch grains are observed in older cells of endosperm. The embryo development is regular and conforms to Pooid type.

Decarboxylases in the immature solid endosperm of the coconut ( Cocos nucifera)

The glutamic acid decarboxylase activity of the solid endosperm of the immature coconut, 6–8 months after opening of the spathe, was studied manometrically. The activity was found to be small and to decrease with increasing maturity of the endosperm. A very active pyruvic acid decarboxylase was found. Aspartic acid decarboxylase and α-ketoglutaric acid decarboxylase activities were negligible. Figures are given for the volume of liquid endosperm, weight, and moisture content of solid endosperm of the drupes used in the study.

Purine-Like Substances from Coconut Endosperm and Their Effect on Senescence in Excised Cereal Leaves

The endosperm of young nuts of Cocos nucifera L. consists of a thin gelatinous layer of jelly and a liquid known as coconut water or milk. As the nuts ripen the jelly develops into a thick, firm, white meat. Steward and his collaborators consider that the specific growth-promoting activity of coconut water results from a synergistic interaction between an inactive neutral fraction, containing hexitols, and an active fraction (8, 11, 17). The latter contains several active substances, one of which is 1,3-diphenylurea (13) and some of which are purine-like (11, 12) though they do not resemble any known purines or pyrimidines. Although Mauney *et al. (4) concentrated a growth-promoting fraction from coconut meat, pure substances were not isolated nor have kinetin or kinetin-like substances been isolated from coconut water (18). In this paper we report the occurrence in extracts from the solid endosperm of young coconuts of purine-like substances which delay senescence in detached cereal leaves as do kinetin (7, 10) and benzimidazole (9). Our interest in this problem stems partly from our interest in the possible role of similar naturally-occurring substances in the formation of green islands at rust and mildew infections.

Free Amino-acids in the Endosperm of the Developing Coconut (Cocos nucifera)

The free amino-acids in the sap flowing from the incised inflorescence of the coconut palm (Cocos nucifera) and in the liquid and solid endosperm of the coconut at various stages of development (4-12 months from the time of opening of the spathe) have been studied by paper and ion-exchange chromatography. The chief amino-acids in the sap were in decreasing order of magnitude: glutamic acid, aspartic acid, glutamine, serine, and asparagine. Smaller amounts of threonine, alanine, y-aminobutyric acid, proline, valine, arginine, and trypto phan were found, along with traces of tyrosine, /9-alanine, lysine, histidine, leucine, isoleucine, and methionine. The chief amino-acids in the liquid endosperm of the nut until 6 months of age were alanine, glutamic acid, serine, valine, and proline with smaller amounts of asparagine, aspartic acid, glycine, threonine, leucine, isoleucine, and glutamine. The alanine, glutamic acid, proline, and y-aminobutyric acid contents of the liquid endosperm increased greatly as the solid endosperm was laid down, ultimately forming about 75 per cent, of the total free amino-acids. Nineteen amino-acids were detected at the 8-io-month stage. y-Aminobutyric acid appears in the liquid endosperm soon after the solid endosperm commences to form, and increases strikingly thereafter. It was also found in the free amino-acids of the solid endosperm at all stages of development. This amino-acid was not found in the acid hydrolysate of coconut globulin. The free amino-acids in the solid endosperm were found to reflect qualitatively the free amino-acid composition of the corresponding liquid endosperm. In addition, /3-alanine, a-aminobutyric acid, phenylalanine, and tryptophan were present in small amounts. Alanine, serine, glutamic acid, and y-aminobutyric acid increased with age of the nut while the others increased up to 6 months and then decreased, only traces being found at maturity except in the case of aspartic acid, proline, and threonine. Twenty-one amino-acids were detected in the free amino-acids of the solid endosperm. The source of the free amino-acids in the liquid endosperm and the possible use of these amino-acids for protein synthesis in the coconut are briefly discussed.

Gamma-amino-butyric acid and other free amino-acids in the coconut.

γ-AMINO-BUTYRIC acid has been described as present in the aqueous and alcoholic extracts of a number of plant and animal tissues1–7. In the course of studies on the nitrogenous constituents of coconut (Cocos nucifera) endosperm using paper chromatography, I have found this amino-acid to be present in amounts apparently larger than any other amino-acid except alanine in the watery liquid inside the mature fruit. Further investigations at three consecutive stages of development, namely, 4–5 months, 5–6 months and 6–7 months after setting of the fruit revealed that γ-amino-butyric acid is not present in the liquid endosperm at 4–5 months after setting of the fruit, but makes its appearance in the liquid when the solid endosperm has been deposited as a thin gelatinous layer on the nucellus in the fifth to sixth month after setting.

Effect of Coconut Endosperm and Other Growth Stimulants upon the Development In vitro of Embryos of Cocos nucifera

1. The best growth in vitro of coconut embryos was obtained in sterile filtered liquid endosperm (milk) from green coconuts. Heating the young depressed its growth-promoting activity. 2. Milk from mature coconuts was markedly inhibitory to the growth of excised embryos; the inhibitory factor was heat-stable. 3. Mature cellular endosperm was also inhibitory to embryo growth. This inhibition was greater in the dark than in the light. The inhibitory activity of mature milk was accentuated by the addition of mature cellular endosperm. Young cellular endosperm did not inhibit embryo growth. 4. These experiments suggest that factors inhibitory to the growth of coconut embryos may develop in the milk and solid endosperm of coconut as the fruit matures and may function in initiating and maintaining the dormancy of the embryo.

Investigations on Growth and Metabolism of Plant Cells

By the carrot-assay method it has been shown that the watery endosperm of coconut contains the growth-promoting coconut-milk factor at all stages of development. Some activity is shown by the parts of the immature embryo but not by the solid endosperm. Sources of analogous activity are in the endosperm of Zea mays in the milk stage, the gelatinous content of immature fruits of Fuglans regia, and the young gametophyte of Ginkgo biloba. The data for other cases examined suggest that the material develops best in nutritive tissues associated with delayed embryo development.