Some observations on plant lectins and Rhizobium specificity

The ability of fluorescein isothiocyanate (FITC) labelled lectins extracted from the legumes Aspalathus linearis, Glycine max, Lotononis bainesii, Phaseolus vulgaris and Pisum sativum, respectively, to react with strains of various Rhizobium spp. was studied. With the exception of six out of ten strains of R. phaseoli and two out of ten strains of R. japonicum, none of the Rhizobium strains tested were able to bind lectin from their normal host plants. Many strains of R. leguminosarum, R. trifolii and R. phaseoli bound each of the plant lectins studied with the exception of the P. sativum lectin. This lectin was only bound by two strains of R. meliloti and a slow-growing strain isolated from Macroptilium atropurpureum. These results do not support suggestions by other workers that plant lectins play an important role in Rhizobium specificity.     

THE EFFECT OF PESTICIDES ON THE YIELD AND BOTANICAL COMPOSITION OF A NEWLY-SOWN RYEGRASS LEY AND OF AN OLD MIXED PASTURE

Newly-sown S24 perennial ryegrass at Hurley and old established ryegrass-dominant mixed pasture at Rothamsted were treated with several pesticides, singly and in combination, over the period 1969–73. Yields were either unaffected or increased by up to 30% in any one year, depending on the treatment, the newly-sown sward giving the more consistent response from year to year.     

Fucose-Rich Sulfated Polysaccharides from Two Vietnamese Sea Cucumbers Bohadschia argus and Holothuria (Theelothuria) spinifera: Structures and Anticoagulant Activity

Fucosylated chondroitin sulfates (FCSs) FCS-BA and FCS-HS, as well as fucan sulfates (FSs) FS-BA-AT and FS-HS-AT were isolated from the sea cucumbers Bohadschia argus and Holothuria (Theelothuria) spinifera, respectively. Purification of the polysaccharides was carried out by anion-exchange chromatography on DEAE-Sephacel column. Structural characterization of polysaccharides was performed in terms of monosaccharide and sulfate content, as well as using a series of non-destructive NMR spectroscopic methods. Both FCSs were shown to contain a chondroitin core [→3)-β-d-GalNAc-(1→4)-β-d-GlcA-(1→]_n bearing sulfated fucosyl branches at O-3 of every GlcA residue in the chain. These fucosyl residues were different in pattern of sulfation: FCS-BA contained Fuc2S4S, Fuc3S4S and Fuc4S at a ratio of 1:8:2, while FCS-HS contained these residues at a ratio of 2:2:1. Polysaccharides differed also in content of GalNAc4S6S and GalNAc4S units, the ratios being 14:1 for FCS-BA and 4:1 for FCS-HS. Both FCSs demonstrated significant anticoagulant activity in clotting time assay and potentiated inhibition of thrombin, but not of factor Xa. FS-BA-AT was shown to be a regular linear polymer of 4-linked α-L-fucopyranose 3-sulfate, the structure being confirmed by NMR spectra of desulfated polysaccharide. In spite of considerable sulfate content, FS-BA-AT was practically devoid of anticoagulant activity. FS-HS-AT cannot be purified completely from contamination of some FCS. Its structure was tentatively represented as a mixture of chains identical with FS-BA-AT and other chains built up of randomly sulfated alternating 4- and 3-linked α-L-fucopyranose residues.     

Factors affecting seed dormancy and germination of Johnsongrass, Sorghum halepense (L.) Pers.

Seeds of Johnsongrass [Sorghum halepense (L.) Pers.] germinated to higher percentages (20–30% higher) when incubated at 28 and 35° C than at 10 or 22° C. After-ripening was accelerated by dry storage of these seeds at 50°C. Seeds pre-chilled at 6°C for 2–4 weeks followed by incubation at 28°C germinated 40–60%. Light effects on germination were related to incubation temperatures; inhibitory at 22°C; no response at 28°C; and stimulatory at 35°C. Effects of gibberellin A₃ (GA₃) also varied depending on incubation temperature, sodium hypochlorite (NaOCl) immersion and light conditions. Immersion of dry seeds in either 700 mM NaOCl, 900 mM H₂O₂ or concentrated H₂SO₄ before incubation in water was effective in breaking dormancy. This result suggests the modes of action of H₂SO₄ in the termination of dormancy may be similar to those of NaOCl and H₂SO₄ as previously suggested by Hsiao & Quick (1984), that is by modification or scarification of the hull or seed coat membranes, and also by the supply of additional oxygen to the seed.     

Evaluation of non-chemical seed treatment methods for the control of Alternaria dauci and A. radicina on carrot seeds

The current study was initiated to evaluate the efficacy of physical methods (hot water, aerated steam, electron treatment) and agents of natural origin (resistance inducers, plant derived products, micro-organisms) as seed treatments of carrots for control of Alternaria dauci and A. radicina. Control of both Alternaria species by seed treatment with the resistance inducers was generally poor. Results were also not satisfactory with most of the formulated commercial micro-organism preparations. Based on the average of five field trials, one of these, BA 2552 (Pseudomonas chlororaphis), provided a low but significant increase in plant stand. Among the experimental micro-organisms, the best results were obtained with Pseudomonas sp. strain MF 416 and Clonostachys rosea strain IK726. A similar level of efficacy was provided by seed treatment with an emulsion (1%) of thyme oil in water. Good and consistent control was generally achieved with the physical methods aerated steam, hot water and electron treatment. Aerated steam treatment was, apart from the thiram-containing chemical standard, the best single treatment, and its performance may at least partially be due to extensive pre-testing, resulting in dosages optimally adapted to the respective seed lot. In some of the experiments the effect of the hot water treatment, which was tested at a fixed, not specifically adapted dosage, was significantly improved when combined with a Pseudomonas sp. MF 416 or C. rosea IK726 treatment. The results are discussed in relation to the outcome of experiments in which the same seed treatment methods and agents were tested in other seed-borne vegetable pathosystems.