The gum exudates from Chloroxylon swietenia,Sclerocarya caffra,Azadirachta indica and Moringa oleifera

Analytical data are presented for the polysaccharide and proteinaceous components of the gum exudates from Chloroxylon swietenia and Sclerocarya caffra, and for the amino acid compositions of the exudates from Azadirachta indica (two specimens) and Moringa oleifera. The gums from C. swietenia and S. caffra contain 4-O-methylglucuronic acid, glucuronic acid, galactose and arabinose; rhamnose is absent. Amino acid analysis shows that proteinaceous material is present in the gums from C. swietenia, S. caffra and M. oleifera despite their low nitrogen content. Hydroxyproline accounts for 28 % of the amino acid content of S. caffra gum. In contrast, A. indica gum has a high nitrogen content but contains very little hydroxyproline.     

The gum exudates from Brachystegia and Julbernardia species

Analytical data are presented for the water-soluble gum exudates from Brachystegia glaucescens, B. spiciformis, and Julbernardia globiflora. They are acidic polysaccharides containing glucuronic acid, 4-O-methylglucuronic acid and galacturonic acid, together with galactose, minor amounts of arabinose, and relatively high proportions of rhamnose. The exudate from B. glaucescens is of particular interest in having high molecular weight, high intrinsic viscosity, and a high methoxyl content. The nitrogen content of all three gums is low, but amino acid analysis shows that proteinaceous components are involved, as in the gum exudates from other genera.     

The amino acid composition of gum exudates from Prosopis species

The amino acid compositions of the proteinaceous components of the gum exudates from Prosopis alba, P. chilensis, P. glandulosa, P. laevigata, P. torreyana and P. velutina, and for a sample of commercial gum mesquite, are presented. In agreement with data published previously for the polysaccharide components of their gums, only minor differences in composition are shown by these species. The amino acid compositions are characterized by very high proportions of hydroxyproline and by high proportions of proline and serine; these three amino acids account for 62.5% of those present in the gum from Prosopis velutina. The amino acid compositions of these Prosopis gums are remarkably similar to that established recently for the gum from Acacia senegal (gum arabic).     

The proteinaceous components of the gum exudates from some phyllodinous Acacia species

Acacia gum exudates are proteinaceous polysaccharides; their protein content ranges from ca 0.2 to 45%.The data presented show that the amino acid compositions of the gums from 12 phyllodinous species (10 from Bentham's sub-series Uninerves racemosae, two from sub-series Juliflorae) also vary considerably, particularly in respect of their hydroxyproline content (55 residues per 1000 residues in A. aestivalis gum, 287 residues per 1000 in A. saliciformis gum). The proportions of some other amino acids, e.g. alanine, aspartic acid, proline and serine also vary considerably, but the proportions of others, e.g. cystine, methionine, histidine, threonine, tyrosine and valine, are remarkably constant. The amino acid composition of gums with a very low protein content (e.g. A. victoriae and A. mycrobotrya) is similar to that for a highly proteinaceous gum (A. tumida). There are, however, considerable differences between the amino acid compositions of the gums from A. saligna and A. pycnantha (South African and Western Australian specimens). This strengthens previous chemotaxonomic evidence, based on the polysaccharide parameters of their gums, that these two species are not as close taxonomically as was originally believed from morphological considerations.     

Amino acid composition of gum exudates from some african Combretum terminalia and anogeissus species

Amino acid compositions are presented for the proteinaceous components of the gum exudates from Combretum glutinosum (syn. apiculatum), C. zeyheri, C. molle (syn. guenzii), C. psidioides (syn. grandifolium), C. obovatum, C. collinum (syn. binderanum), C. hartmannianum, C. fragrans (syn. ternifolium), Teminalia sericea and T. superba; and for Anogeissus schimperi. The principal amino acids common to these species are aspartic acid, alanine and glycine, but there are considerable variations; glutamic acid, histidine, lysine, proline, serine, threonine and valine are also major components of some of the species studied. The Combretaceae are therefore similar to the Sterculiaceae in containing very low proportions of hydroxyproline, which is the major amino acid component of the gums studied so far from genera within the Mimosoideae.     

Gum polysaccharides from three Parkia species

Nigerian gum exudates from Parkia bicolor and P. biglobosa, and gum from the seed pods of P. pendula growing in Costa Rica have been analysed. The two gum exudates are proteinaceous and have closely similar physicochemical properties and compositions, with galactose, arabinose, glucuronic acid and 4-O-methylglucuronic acid as their constituent sugars; rhamnose is absent, and they are dextrorotatory. The gum from the seed pods of P. pendula contains the same constituent sugars in different proportions, and is laevorotatory. These data may be of interest in the continuing studies of plant-animal interactions and mechanisms of seed dispersal associated with the genus Parkia.     

Some highly proteinaceous Acacia gum exudates of the subseries Juliflorae

Analytical data for the gum exudates from Acacia difficilis, A. dimidiata, A. eriopoda, A. maidenii, A. stipuligera, A. torulosa and A. tumida are presented. Of these, five are highly proteinaceous; they also have high methoxyl contents and very low rhamnose contents. In contrast, A. dimidiata shows no unusual analytical parameters, and A. maidenii gum has alowarabinose content and a high rhamnose content, thus having a sugar composition of the type first observed in the gum from A. saligna. The gum from A. maidenii is also of interest as its analytical data are closely similar to those for A. longifolia, the only other tetramerous member of the subseries Juliflorae to have been studied. The data reported extend even further the unusual ranges of analytical parameters found within the Juliflorae, and confirm its great heterogeneity and chemotaxonomic interest.     

The composition and properties of the gum exudates from Terminalia sericea and T. Superba

The gum polysaccharides from Terminalia sericea and T. superba have been analysed. They have a complex sugar composition, containing galacturonic, glucuronic, and 4-O-methylglucuronic acids as well as galactose, arabinose, rhamnose, mannose and xylose. The exudates from T. sericea and T. superba are remarkably similar in composition, particularly with respect to their proportions of neutral sugars and total uronic acid content, although T. sericea gum contains considerably more 4-O-methylglucuronic acid than T. superba. Both gums are very viscous and dissolve readily to give solutions of good colour.!!     

The composition of the proteinaceous polysaccharides exuded by astragalus microcephalus,A. Gummifer and A. Kurdicus—The sources of turkish gum tragacanth

Gum tragacanth is a variable commodity because commercial samples may legitimately be admixtures, in any relative proportions, of the exudates from Asiatic Astragalus spp. Analytical data show that the exudates collected from the three major contributing Turkish spp., A. microcephalus, A. gummifer and A. kurdicus, differ extensively, particularly in terms of their fucose, xylose, galacturonic acid and methoxyl contents and in the relative proportions of their soluble (tragacanthin) and insoluble (bassorin) components. In addition, these three Astragalus exudates are shown to be proteinaceous polysaccharides; their amino acid compositions differ, particularly in terms of their hydroxyproline, histidine, aspartic acid and arginine content. In contrast, the amino acid compositions of the soluble and insoluble components of A. kurdicus do not differ extensively.     

Analytical comparison of gums from Acacia hebeclada and other gummiferae species

Analysis of the arabinogalactan-protein isolated from a specimen of Acacia hebeclada gum has shown major differences in composition between this and a specimen previously examined in another laboratory. In its much lower proportions of protein and uronic acid, and higher arabinose content, the present specimen of A. hebeclada gum resembles more closely gum from the taxonomically related species A. tortilis, this similarity extending to the modes of linkage of the constituent sugar and uronic acid residues. The hydroxyproline content of the protein moiety is also close to that in A. tortilis gum. The wide variation in composition between different specimens of A. hebeclada gum is comparable with that of the gums of A. karroo and A. erioloba, from the same series (Gummiferae Benth.).     

New sources of water-soluble seed gums

Seeds from 300 species representing 139 genera in 31 plant families have been surveyed for water-soluble gum (mucilage). Four families, Leguminosae, Plantaginaceae, Cruciferae, and Convolvulaceae, have species the seeds of which contain more than 18% gum. The legumes were studied most intensively. Of 163 legume species in 45 genera, 36 contained more than 18% gum, and 54 contained 10 to 18%. Gums from 20 legumes have been analyzed for component sugars; these are all galactomannans. Their specific optical rotation increases regularly as the mannose content decreases. In the legume seed, gum often comprises most of the endosperm. These galactomannan gums can be separated by a milling process to provide commercial-grade gums useful for paper additives and for sizing, thickening, or stabilizing agents.     

Gum exudates from the genus Grevillea (Proteaceae)

Analytical data are presented for gum specimens from Grevillea agrifolia, G. candelabroides, G. robusta, G. striata, and G. wickhamii (two specimens), and brief botanical details of this large, complex genus are given. The gum exudates, which are of high molecular weight, show good solubility and give solutions that are much more viscous than any of the Acacia exudates studied so far; they may therefore be of industrial interest.     

The gum exudates from some acacia subspecies of the series botryocephalae

Gum specimens from A. deanei subsp. paucijuga (two samples), A. irrorata subsp. irrorata, and A. dealbata subsp. subalpina have been analysed. There are minor differences between the two specimens from A. deanei subsp. paucijuga, but they, and the gum from A. irrorata subsp. irrorata, have analytical parameters that correspond well with those for species in the proposed Group A within the Botryocephalae. In contrast, the gum from A. dealbata subsp. subalpina conforms well with the analytical parameters established for A. dealbata gum, and the slight analytical differences lead to it being assigned with greater confidence to the proposed Group B. Now that the gum exudates from approximately 40% of the species within the Botryocephalae have been studied and shown to fall into two different types, it is hoped that the chemical data may be meaningful taxonomically.     

The gum exudates from some closely related Acacia species of the subseries Uninerves racemosae (section phyllodineae)

Australian gum specimens from Acacia aestivalis, A. chrysella, A. jennerae and A. microbotrya (five specimens differing slightly in some morphological characters) have been studied. These species, placed within Bentham's Series 1, subseries 6F (Uninerves racemosae) are closely related, forming part of the recognized A. microbotrya group. The five specimens from A. microbotrya show minor variations, similar in extent to those established previously for gums from other species. The gums from A. chrysella and A. jennerae are similar to those from A. microbotrya in chemical composition. The gum from A. aestivalis differs from those from A. microbotrya, A. chrysella and A. jennerae in two main respects: it is more acidic and has a much higher methoxyl content. Thus significant differences in gum composition can be shown by some species that differ only slightly in morphological characters. Data for the amino acid compositions of the proteinaceous components of the gums from A. aestivalis, A. jennerae and A. microbotrya, differ considerably from those for the gums from other species belonging to the Uninerves racemosae, e.g. A. saliciformis and A. xanthina, which are much more viscous and have higher proteinaceous contents containing much higher proportions of the amino acids commonly involved in linkages with sugars. Of the closely related species studied, A. aestivalis is closer to A. microbotrya than A.jennerae in terms of the amino acid compositions of their gums, a reversal in the relative affinities shown by their polysaccharide parameters. Thus amino acid compositions are of interest chemotaxonomically and also in terms of the tertiary structures of Acacia gum exudates.     

Performance of vesicular-arbuscular mycorrhizae in saline-alkali soil in relation to various amendments

The present study shows that vesicular-arbuscular mycorrhizal colonization in plants grown in saline-alkali soil is host dependent and it is significantly affected by various amendments given to reclaim such soils. Maximum reduction in vesicular-arbuscular mycorrhizal colonization was observed in the plants raised in saline-alkali soil amended with gypsum and maximum colonization was observed after plant-growth promoting rhizobacterium or farm yard manure amendments. Plants possessing high level of vesicular-arbuscular mycorrhizal colonization (50–70%) included Acacia nilotica, Albizia lebbeck and Dalbergia sissoo. Casuarina equisetifolia possessed moderate level of vesicular-arbuscular mycorrhizae colonization (30–50%) and Azadirachta indica possessed low level of colonization (20–40%).     

The composition of the gum exudates from some combretum species; the botanical nomenclature and systematics of the combretaceae

An analytical study has been made of gum specimens from Combretum collinum, C. collinum subsp. hypopilinum, C. erythrophyllum, C. nigricans, C. fragrans, and C. glutinosum. In comparison with the genus Acacia, both the botanical classification and synonymy, and the chemistry, are more complex. Glucuronic acid, galacturonic acid, 4-O-methylglucuronic acid, galactose, arabinose, and rhamnose are present in all the specimens studied. In addition, mannose and xylose are present in the gum from C. collinum, which is therefore similar to C. hartmannianum. The data now available suggest that, as a group, the genus Combretum produces gum exudates that are more viscous, of higher molecular weight, and more acidic than those of the Acacia group.     

Acacia gum exudates from species of the series gummiferae

An analytical study of the gum exudates from the African species Acacia ehrenbergiana (three specimens), A.xanthophloea (two specimens), A.hockii and A.sieberana var.villosa, and of the Australian species A.calcigera, has been made. There are now 19 species within the series Gummiferae Benth. for which gum parameters are available; of these, only A. ehrenbergiana gum displays a slightly negative optical rotation. The data for the three gum specimens from A. ehrenbergiana give a further example of the extent to which the gum from different trees of one particular species can vary in composition. The data for A.sieberana var. villosa gum are compared with the values established previously for subsp. sieberana; the differences between varieties of one species are similar in extent to those established for some subspecies. Although A. xanthophloea, A. hockii, A. ehrenbergiana, A. seyal and A. karroo are regarded as being very closely related botanically, the values for some of their analytical parameters differ considerably and strongly support the view that it is correct to retain them as distinct species.     

Composition of gum exudates from Anacardium occidentale

The composition and solution properties of Indian and Papuan specimens of the gum from Anacardium occidentale have been studied and found to be closely similar. Contrary to earlier reports by Indian workers, this gum does not contain galacturonic acid. It does, however, contain glucose; this appears to be the first report of the presence of this sugar in a plant gum exudate. A freeze-dried sample of the gum was examined at intervals over a period of 2 months; its weight-average MW increased by a factor of three in that time, and molecular-sieve chromatography showed that self-association occurred with the formation of a small proportion of a very high MW component.     

Differential Inactivation of Seed Exudate Stimulation of Pythium ultimum Sporangium Germination by Enterobacter cloacae Influences Biological Control Efficacy on Different Plant Species

This study was initiated to understand whether differential biological control efficacy of Enterobacter cloacae on various plant species is due to differences in the ability of E. cloacae to inactivate the stimulatory activity of seed exudates to Pythium ultimum sporangium germination. In biological control assays, E. cloacae was effective in controlling Pythium damping-off when placed on the seeds of carrot, cotton, cucumber, lettuce, radish, tomato, and wheat but failed to protect corn and pea from damping-off. Seeds from plants such as corn and pea had high rates of exudation, whereas cotton and cucumber seeds had much lower rates of exudation. Patterns of seed exudation and the release of P. ultimum sporangium germination stimulants varied among the plants tested. Seed exudates of plants such as carrot, corn, lettuce, pea, radish, and wheat were generally more stimulatory to P. ultimum than were the exudates of cotton, cucumber, sunflower, and tomato. However, this was not directly related to the ability of E. cloacae to inactivate the stimulatory activity of the exudate and reduce P. ultimum sporangium germination. In the spermosphere, E. cloacae readily reduced the stimulatory activity of seed exudates from all plant species except corn and pea. Our data have shown that the inability of E. cloacae to protect corn and pea seeds from Pythium damping-off is directly related to its ability to inactivate the stimulatory activity of seed exudates. On all other plants tested, E. cloacae was effective in suppressing damping-off and inactivating the stimulatory activity of seed exudates.     

Nematode Genera in Forest Soil Respond Differentially to Elevated CO2

Previous reports suggest that fungivorous nematodes are the only trophic group in forest soils affected by elevated CO₂. However, there can be ambiguity within trophic groups, and we examined data at a genus level to determine whether the conclusion remains similar. Nematodes were extracted from roots and soil of loblolly pine (Pinus taeda) and sweet gum (Liquidambar styraciflua) forests fumigated with either ambient air or CO₂-enriched air. Root length and nematode biomass were estimated using video image analysis. Most common genera included Acrobeloides, Aphelenchoides, Cephalobus, Ditylenchus, Ecphyadorphora, Filenchus, Plectus, Prismatolaimus, and Tylencholaimus. Maturity Index values and diversity increased with elevated CO₂ in loblolly pine but decreased with elevated CO₂ in sweet gum forests. Elevated CO₂ treatment affected the occurrence of more nematode genera in sweet gum than loblolly pine forests. Numbers were similar but size of Xiphinema decreased in elevated CO₂. Abundance, but not biomass, of Aphelenchoides was reduced by elevated CO₂. Treatment effects were apparent at the genus levels that were masked at the trophic level. For example, bacterivores were unaffected by elevated CO₂, but abundance of Cephalobus was affected by CO₂ treatment in both forests.