Contagious dispersal of seeds of synchronously fruiting species beneath invasive and native fleshy-fruited trees

In subtropical Australia, many native and invasive plant species rely on a shared suite of frugivores, largely birds, for seed dispersal. Many native plants fruit during summer in this region, whereas most invasive plants fruit during winter, thus providing the opportunity for contagious dispersal of seeds beneath synchronously fruiting species. We sampled invasive and native seed rain beneath the canopy of a native summer-fruiting tree Guioa semiglauca and an invasive winter-fruiting tree Cinnamomum camphora, in three study sites over the course of a year. In July, during peak fruiting season for C. camphora and other invasive species, seed rain of invasive species was higher beneath C. camphora than G. semiglauca. This was partly due to the invasive tree Ligustrum lucidum, whose seed rain was three times higher beneath C. camphora than beneath the native tree. In February, seed rain of native species was more abundant beneath the canopy of G. semiglauca than beneath C. camphora, despite the fact that C. camphora was also fruiting at this time. This was probably due to the larger fruit crop produced by G. semiglauca at this time of year. Our study provides evidence that the presence of invasive bird-dispersed plants may facilitate contagious seed dispersal of other invaders, and likewise native species may facilitate seed spread of other native plants.

NMR study of the oil build-up in sunflower seeds

THE use of NMR to investigate the quality of the oil as a function of maturity of the seeds is demonstrated for sunflower seeds. The percentages of the saturated and individual unsaturated aids are determined as a function of time after flowering of the seeds. The percentage of saturated fatty acids is found to decrease with maturity of seeds whereas the extent of the unsaturated acids increases.

Responses of tribolium castaneum to olfactory cues from cotton seeds, the fungi associated with cotton seeds, and cereals

We tested, in an olfactometer, whether or not Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) responds preferentially to the volatiles that emanate from the fungi associated with cotton [Gossypium hirsutum L. (Malvaceae)] seed over those that emanate from cereals, because cereals are usually portrayed as the primary resources of these beetles. Pairwise comparisons were conducted between cotton seed, wheat (Triticum aestivum L.), and sorghum [Sorghum bicolor (L.) Moench] (both Poaceae); volatiles were tested from intact seeds and from both water and ethanol extracts. The results demonstrate that T. castaneum is attracted more strongly to cotton seeds with its lint contaminated with fungi, than to the conventional resources of this species (i.e., wheat and sorghum). Further tests prove that it is the fungus on the lint that produces the active volatiles, because the beetles did not respond to sterilized cotton lint (i.e., without the fungi typically associated with it when cotton seed is stored). Tests with five fungal cultures (each representing an unidentified species that was isolated from the field-collected cotton lint) were variable across the cultures, with only one of them being significantly attractive to the beetles. The others were not attractive and one may even have repulsed the beetles. The results are consistent with the beetles having a strong ecological association with fungi and suggest it would be worth investigating the ecology of T. castaneum from this perspective. © 2012 The Netherlands Entomological Society.

Germinating the seeds of three species of Pimelea sect. Epallage (Thymelaeaceae)1

Pimelea trichostachya Lindl., P. simplex F.Muell. and P. elongata Threlfall frequently cause pimelea poisoning of cattle. Fresh seeds of these species, belonging to sect. Epallage (Endl.) Benth. of Pimelea Gaertn. (Thymelaeaceae) are strongly dormant for years when in laboratory storage. Common methods of stimulating germination, such as scarification, dry heat and cold stratification, did not remove much of the dormancy. ‘Smoke water’ stimulated some germination but its effect was unpredictable and many seedlings then grew aberrantly. Exposure of imbibed seeds to gibberellic acid greatly and reliably improved the germination of all three species. However, the manner of application and the concentration of gibberellic acid used had to be appropriate or many young seedlings grew abnormally or died suddenly, limiting successful plant establishment rates. The dormancy type involved is non-deep Type 2 physiological. Ten days of good moisture, in addition to gibberellic acid exposure, is required before appreciable laboratory germination occurs at optimal temperatures. Thus, the mechanism by which gibberellic acid stimulates good germination does not appear to be the same as that which primes seeds for the rapid and prolific germination often seen under natural conditions in arid Australia. Seeds of P. simplex subsp. continua (J.M.Black) Threlfall proved most difficult to germinate and those of P. elongata the easiest.

Carbohydrate binding specificity of the B-cell maturation mitogen from Artocarpus integrifolia seeds

Artocarpin, a mannose-specific lectin, is a homotetrameric protein (M(r) 65,000) devoid of covalently attached carbohydrates and consists of four isolectins with pI in the range 5-6.5. Investigations of its carbohydrate binding specificity reveal that among monosaccharides, mannose is preferred over glucose. Among mannooligosaccharides, mannotriose (Man alpha 1-3[Man alpha 1-6]Man) and mannopentaose are the strongest ligands followed by Man alpha 1-3Man. Extension of these ligands by GlcNAc at the reducing ends of mannooligosaccharides tested remarkably improves their inhibitory potencies, while substitution of both the alpha 1-3 and alpha 1-6 mannosyl residues of mannotriose and the core pentasaccharide of N-linked glycans (Man alpha 1-3[Man alpha 1-6]Man beta 1-4GlcNAc beta 1-4GlcNAc) by GlcNAc or N-acetyllactosamine in beta 1-2 linkage diminishes their inhibitory potencies. Sialylated oligosaccharides are non-inhibitory. Moreover, the substitution of either alpha 1-3 or alpha 1-6 linked mannosyl residues of M5Gn or both by mannose in alpha 1-2 linkage leads to a considerable reduction of their inhibitory power. Addition of a xylose residue in beta 1-2 linkage to the core pentasaccharide improves the inhibitory activity. Considering the fact that artocarpin has the strongest affinity for the xylose containing hepasaccharide from horseradish peroxidase, which differs significantly from all the mannose/glucose-specific lectins, it should prove a useful tool for the isolation and characterization of glycoproteins displaying such structure.

The Isolation and Characterization of β-N-Oxalyl-L-α,β-Diaminopropionic Acid: A Neurotoxin from the Seeds of Lathyrus sativus

A neurotoxic compound has been isolated from the seeds of Lathyrus sativus in 0.5% yield and characterized as β-N-oxalyl-L-α,β-diaminopropionic acid. The compound is highly acidic in character and forms oxalic acid and diaminopropionic acid on acid hydrolysis. The compound has a specific rotation of -36.9° and has apparent pK values in the order of 1.95, 2.95, and 9.25, corresponding to the two carboxyl and one amino functions, respectively. The compound has been synthesized by reacting an aqueous methanolic solution of the copper complex of L-α,β-diaminopropionic acid prepared at pH 4.5-5.0 with dimethyl oxalate under controlled pH conditions and isolating the compound by chromatography on a Dowex 50-H+ column after precipitating the copper. The compound induced severe neurological symptoms in day-old chicks at the level of 20 mg/chick, but not in rats or mice. It also inhibited the growth of several microorganisms and of the insect larva Corcyra cephalonica Staint. L-Homoarginine had no neural action in chicks. It is suggested that the neurotoxic compound is species specific in its action and may be related to "neurolathyrism" associated with the human consumption of L. sativus seeds.

Crystallization and preliminary X-ray studies of a galactose-specific lectin from the seeds of bitter gourd (Momordica charantia)

A galactose-specific lectin from the seeds of bitter gourd (Momordica charantia) is a four-chain type II ribosome-inactivating protein (RIP) resulting from covalent association through a disulfide bridge between two identical copies of a two-chain unit. The available structural information on such four-chain RIPs is meagre. The bitter gourd lectin was therefore crystallized for structural investigation and the crystals have been characterized. It is anticipated that the structure of the orthorhombic crystals will be analysed using molecular replacement by taking advantage of its sequence, and presumably structural, homology to normal two-chain type II RIPs.

Triacylglycerol synthesis in developing seeds of groundnut (Arachis hypogaea): Pathway and properties of enzymes of sn-Glycerol 3-phosphate formation

The enzymatic pathway for the synthesis of sn-glycerol 3-phosphate was investigated in developing groundnut seeds (Arachis hypogaea). Glycerol-3-phosphate dehydrogenase was not detected in this tissue but an active glycerokinase was demonstrated in the cytosolic fraction. It showed an optimum pH at 8.6 and positive cooperative interactions with both glycerol and ATP. Triosephosphate isomerase and glyceraldehyde-3-phosphate phosphatase were observed mainly in the cytosolic fraction while an active glyceraldehyde reductase was found mainly in the mitochondrial and microsomal fractions. The glyceraldehyde 3-phosphate phosphatase showed specificity and positive cooperativity with respect to glyceraldehyde 3-phosphate. The glyceraldehyde reductase was active toward glucose and fructose but not toward formaldehyde and showed absolute specificity toward NADPH. It is concluded that in the developing groundnut seed, sn-glycerol 3-phosphate is synthesized essentially by the pathway dihydroxyacetone phosphate ? glyceraldehyde 3-phosphate ?Pi glyceraldehyde ?NADPH glycerol ?ATP glycerol 3-phosphate. All the enyzmes of this pathway showed activity profiles commensurate with their participation in triacylglycerol synthesis which is maximal during the period 15�35 days after fertilization. Glycerokinase appears to be the rate-limiting enzyme in this pathway.

Charred seeds in Mikkeli Orijärvi : A study of subsistence strategies of an Iron Age settlement in East Finland

In this study the over 350 macrofossil samples, containing over 2300 charred plant remains from an Iron Age settlement containing fossil fields in Mikkeli Orijärvi Kihlinpelto, were studied archaeobotanically. The aim was to get more information about subsistence strategies, especially agriculture and study differences in the plant combinations in the different structures and use the archaeobotanical theory to interpret these structures. The methodological question was to study the taphonomy of the charred plant material. The results gave a diverse impression of the agriculture and subsistence strategies of the settlement in Orijärvi, where barley was the most important cereal with rye, wheat and oat cultivated as minor crops. The arable weed assemblage indicates that the fields were situated in different kinds of soils and the crops were cultivated when different kind of weather conditions were prevailing. Ergot was found with the cereals, and it was growing on some of the arable crops and it also indicates wet climate. Hemp and flax were cultivated and wild plants were collected. The meadow and wetland plants found in the material derive most probably from animal fodder. Tubers of bulbous oat-grass were interesting, because they are usually found in graves. Comparison with other Iron Age settlements and graves indicates that the plant material found from the ancient field layers derives most probably from dwellings and graves, which were taken into cultivation.