Identification of mono-, oligo-, and polysaccharides secreted from soybean roots

The mist culture system was conducted to study secreted polysaccharides from soybean (Glycine max) roots grown for 15 days. Roots were rinsed with distilled water (DW) for 15 min, then with 30 mM oxalic acid (OXA) for 15 min to remove ionically bound sugar. Released sugars were further fractionated into low (L) and high (H) molecular weight fractions with Sephadex G-10. DW rinsing released 190 μg neutral sugar (NS) and 62 μg uronic acid (UA) per plant, while 374 μg NS and 70 μg UA per plant were released by OXA rinsing. Acetylation analysis revealed that the L fraction by DW and OXA mainly consisted of glucose (Glc), pinitol, and UA, whereas the H fraction mainly consisted of arabinose (Ara), galactose (Gal), Glc, and UA. The presence of rhamnose (2%–6%) in both fractions suggests secretion of rhamnogalacturonans. Methylation analysis revealed that the H fraction by DW and OXA contained T-Ara, 3-, 6-, and 3,6-Gal, suggesting the presence of type II arabinogalactan and arabinogalactan proteins. HPLC analysis detected mono-, di-, and tri-GalA in the L fraction by DW and OXA. Substances corresponding to sucrose, kojibiose, cello- and laminari-oligosaccharides were also found in root exudates. Received: August 14, 2001 / Accepted: October 29, 2001     

Some soil-plant and root-shoot relationships of copper,zinc and manganese in white clover and perennial ryegrass

Summary White clover and perennial ryegrass were grown separately, in pots maintained under controlled environment conditions, for a period of 7 months on ten soils. The proportion of the total soil content of each element taken up by the ryegrass, including that in roots, ranged from 0.88 to 2.18% for Cu, from 0.82 to 2.80% for Zn and from 0.25 to 3.15% for Mn. Uptake by the clover was within these ranges for Cu and Zn, but ranged from 0.10 to 1.71% for Mn.After adjustment for the effects of soil contamination, the ratio of root concentration: shoot concentration was always greater than 1 for both Cu and Zn, and for Cu, though not for Zn, it was considerably greater with ryegrass than with clover. For Mn, the ratio of root:shoot concentration was often greater than 1, and differences between clover and grass were not consistent.Concentrations of Cu and Zn in the shoots were always greater in the clover than in the grass, but concentrations of Mn were generally greater in the grass than the clover.     

Development of a model system to assess the impact of genetically modified corn and aubergine plants on arbuscular mycorrhizal fungi

We developed an experimental model system to monitor the impact of generically modified (GM) plants on arbuscular mycorrhizal (AM) fungi, a group of non-target soil microorganisms, fundamental for soil fertility and plant nutrition. The system allowed us to study the effects of root exudates of both commercial Bt corn and aubergine plants expressing Dm-AMP1 defensin on different stages of the life cycle of the AM fungal species G. mosseae. Root exudates of Bt 176 corn significantly reduced pre-symbiotic hyphal growth, compared to Bt 11 and non-transgenic plants. No differences were found in mycelial growth in the presence of Dm-AMP1 and control plant root exudates. Differential hyphal morphogenesis occurred irrespective of the plant line, suggesting that both exuded Bt toxin and defensin do not interfere with fungal host recognition mechanisms. Bt 176 affected the regular development of appressoria, 36% of which failed to produce viable infection pegs. Our experimental model system represents an easy assay for testing the impact of GM plants on non-target soil-borne AM fungi.     

Invasion of naturally senescing root cortices of cereal and grass seedlings byMicrodochium bolleyi

Summary In glasshouse experiments, invasion of wheat and grass (Dactylis glomerata) seedling roots byMicrodochium bolleyi was strongly correlated with the pattern and rate of natural senescence of the root cortex. The fungus did not enhance cortical senescence and did not damage roots except in a few instances when it invaded and killed their tips.M. bolleyi behaved as a weak parasite, largely restricted to invasion of naturally senescing cortices of cereal and grass roots.     

Smash ridge tillage strongly influence soil functionality,physiology and rice yield

The practice of smash-ridging on dry land crop cultivation has shown much promise. However, the mechanism how does soil functionality and root traits can affect rice yield under smash ridge tillage with reduced nitrogen fertilization have not yet been explored. To fill this knowledge gap, we used three tillage methods—smash-ridging 40 cm (S40), smash-ridging 20 cm (S20), and traditional turn-over plowing 20 cm (T)—and two rice varieties (hybrid rice and conventional rice) and measured soil quality, root traits, rice yield and their correlation analysis at different growth stages. Soil physical and chemical properties were significantly improved by smash-ridging, including improvements in root morphological and physiological traits during three growth stages compared with T. S40 had the highest leaf area index (LAI), plant height (PH), and biomass accumulation (BA). Increment in biomass and panicle number (PN) resulted in higher grain yield (GY) of 6.9–9.4% compared with T. Correlation analysis revealed that root total absorption area (RTAA), root active absorption area (RAA), and root area ratio (RAR) were strongly correlated with soil quality. Root injury flow (RIF) and root biomass accumulation (RBA) were strongly correlated with LAI and above-ground plant biomass accumulation (AGBA). Conclusively, S40 is a promising option for improving soil quality, root traits, and consequently GY.     

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.     

Immunofluorescence localization of chalcone synthase in roots ofPisum sativum L. andPhaseolus vulgaris L. and comparable immunochemical analysis of chalcone synthase from pea leaves

Summary Chalcone synthase in roots ofPisum sativum andPhaseolus vulgaris was demonstrated enzymatically and immunochemically. In situ localization by indirect immunofluorescence revealed that chalcone synthase is chiefly present in the lateral regions of the calyptra, in the rhizodermis, and the cortex. In the central cylinder the enzyme protein is no longer detectable a short distance behind the meristem. Chalcone synthase was not found in root tips ofZea mays. Two isoforms of chalcone synthase were separated by chromatofocusing of protein extracts from pea leaves. The two forms differed in their subunit molecular masses. The smaller isoform was not detected in roots.Abbreviations CHS chalcone synthase - FITC fluorescein isothiocyanate - IgG immunoglobulin G - DTE dithioerythritol     

Quantification by ELISA of Cytokinins in Root-Pressure Exudates of Urtica dioica Plants Grown under Different Nitrogen Levels

ELISAs for [9R]iP, [9R]Z and (diH) [9R]Z have been worked out which, in combination with HPLC., allow the quantitative determination of cytokinins of the isopentenyladenin-, zeatin- and dihydrozeatin-type in samples of plant material. The three ELISAs are optimally applicable in the range from 0.5 to 20 pmoles of cytokinins per assay but reliable measurements can still be performed down to 0.05 pmoles. The assay has been applied to root pressure exudates obtained from Urtica dioica plants grown under controlled conditions and at different nitrogen (nitrate) levels. The predominant cytokinins of the xylem exudate were Z, Z-nucleotide, iP, [9R]iP and iP-nucleotide, while (diH)Z was present to a minor extent. The concentrations of these compounds were found to range between 0.2 and 3 pmoles per ml exudate. Interestingly, no effect of the different nitrogen nutrition on the pattern and concentration of cytokinins in the xylem exudate could be established.