Wayne T. Buckley

A rapid, seedling-based bioassay for identifying low cadmium-accumulating individuals of Durum wheat (Triticum turgidum L.)

We have developed a seedling-based bioassay that iscapable of identifying low Cd-accumulating phenotypes(homozygous and heterozygous) after 96–120 h ofexposure. Our experiments were conducted using109Cd as a tracer at subtoxic concentrations tosimulate conditions that might be experienced in thefield. Supply of Cd (10-11 M) to 4-d oldseedlings for 0–8 h resulted in no differences in rootand leaf Cd content between the low (TL05) and high(TL04) Cd-accumulating isolines. Increasing time ofexposure produced significant differences in leaf Cdaccumulation between isolines, with differencesbecoming most pronounced after the bulk of appliedcadmium (∼ 95%) was depleted from absorption solutions(≥ 72 h). Similar results were obtained with8-d old seedlings, where differences between genotypeswere more pronounced in young leaves (2nd leaf) orshoot bases. Individuals from five low and highCd-accumulating near isogenic pairs (50individuals/isoline) were screened using Cdconcentration of shoot bases as the screeningcriterion. Mean scores within each isoline pair weresignificantly different, although overlap ofindividual scores was observed at intermediate foliarCd concentrations. The 2nd leaf to root Cdcontent ratio, which reflects root to shoottranslocation, provided a better parameter todistinguish low from high Cd-accumulating isolines. Plants used for this bioassay could also be rescuedfor subsequent experimental crosses, providing a rapidand cost-effective tool for early detection of the lowCd-accumulating phenotype.

A fast ethanol assay to detect seed deterioration

The most common way to test seed quality is to use a simple and reliable but time- and space-consuming germination test. In this paper we present a fast and simple method to analyse cabbage seed deterioration by measuring ethanol production from partially imbibed seeds. The method uses a modified breath analyser and is simple compared to gas chromatographic or enzymatic procedures. A modified method using elevated temperatures (40°C instead of 20°C) shortened the assay time and improved its sensitivity. The analysis showed an inverse correlation between ethanol production and seed quality (e.g. the final percentages or speed of germination and the number of normal seedlings). The increase in ethanol production was observed when cabbage seeds were deteriorated by storage under ambient conditions or hot water treatments, both of which reduced the number of normal seedlings. Premature seeds produced more ethanol upon imbibition than mature seeds. Ethanol production occurred simultaneously with oxygen consumption, indicating that lack of oxygen is not the major trigger for ethanol production.

Root cadmium desorption methods and their evaluation with compartmental modeling

• Desorption of plant roots is often employed in studies of plant physiology and nutrition; however, there have been few studies on the validity of desorption procedures. • Branched and in-line kinetic models with five compartments - cadmium (Cd)-chelate, Cd(2+), root apoplast, root symplast and vacuole - were developed to evaluate the efficacy of diethylenetriaminepentaacetic acid (DTPA) and CaCl(2) methods for the desorption of Cd from roots of durum wheat seedlings. Solution Cd(2+) could exchange with apoplast and symplast Cd simultaneously in the branched model and sequentially in the in-line model. • A 10-min desorption with 1 × 10(-6 )M DTPA at room temperature or cold (0°C) 5 × 10(-3) M CaCl(2) was required to achieve 99% recovery of apoplast-bound (109)Cd when experimental results were interpreted with the branched model. However, when the same data sets were analysed with the in-line model, only partial desorption was achieved. Arguments are presented that suggest that the branched model is correct. • It is suggested that compartmental modeling is a suitable tool for the study of plant root uptake and desorption kinetics, and that there are advantages over more commonly used calculation procedures.

Determination, stable isotope enrichment and kinetics of direct-reacting copper in blood plasma

Abstract Direct-reacting Cu is defined as Cu2+ and other forms of Cu that readily exchange with Cu2+ in blood plasma. An analytical method was developed for 1) quantification of direct-reacting Cu by stable isotope dilution and 2) determination of 65Cu enrichment of direct-reacting Cu in plasma samples from in vivo tracer studies. The method involved addition of enriched 65Cu to plasma, extraction with sodium diethyldithiocarbamate in mineral oil, and analysis by inductively coupled plasma mass spectrometry. Optimum sodium diethyldithiocarbamate concentration for the extraction was 0.16 mM. Direct-reacting Cu (means ± SD) varied from 3.4 ± 0.5% of whole plasma Cu in dairy cows (n = 7) and 3.4 ± 0.3% in healthy men (n = 10) to 16.6 ± 3.7% in dogs (n = 3). After intravenous infusion of enriched 65Cu into two healthy men, biological half-lives of 8.7 and 12.3 min were determined for direct-reacting Cu.

Seed Ethanol Emission and Radicle Protrusion are Better Measures of Canola-Seed Vigor Than Standard Germination

Results of a seed vigor test based on ethanol emission (EE) were compared to rate of emergence (Em50), extent of emergence, seedling mass, and leaf area for 64 lots of open-pollinated and hybrid canola (Brassica napus L.) seed in field plots. The EE test was evaluated against other measures of seed vigor, specifically days to 50% radicle protrusion (R50), 2-d radicle protrusion (R2), seedling fresh mass in hydroponics, cold germination, and a vigor index. Correlation coefficients for R50, R2, and EE versus Em50 were ≥ 0.8 and consistently better than those for standard germination (SG, normal seedlings) for open-pollinated and hybrid propagation types in both the 80%–100% and 90%–100% SG ranges. In contrast to Em50, other aspects of field vigor were not well correlated with vigor tests. It is suggested that EE and R2 are suitable for providing seed quality information to supplement SG results.

Detection of Incipient Germination in Malting Barley with a Starch Viscosity Method and a Proposed Ethanol Emission Method

The risk of germination loss during storage in two-row malting barley can be reduced by identifying grain lots that have undergone incipient germination (IG) during harvest. A method based on starch viscosity that utilizes a Rapid Visco Analyzer (RVA) is currently available for IG analysis. A new potential method, based on the measurement of ethanol emission (EE) from whole barley, may be more efficient and less expensive than the RVA procedure. Three storage experiments were performed: experiments 1 and 3 at 25°C and 80% rh, and experiment 2 in unheated, uninsulated buildings. Decline in germination energy (GE) varied from <1% to about 80% during storage. In experiments 1 and 3, R2 for GE loss (expressed as [weeks to 5% loss of GE]0.2) versus EE was 0.76 in both cases, whereas R2 for GE loss versus RVA viscosity was 0.64 and 0.68, respectively. In experiment 2, the greatest loss of GE was associated with high temperatures and relative humidity in July and August. EE performed as well as RVA in the predic...

An On-Farm Ethanol-Based Color Test for Canola Seed Vigor

An on-farm test for canola (Brassica napus L. and B rapa L.) seed vigor would help ensure that canola growers plant only high-quality seed. A rapid, 24-h color test based on ethanol emission by partially imbibed canola seed is described. Test results were compared to seed vigor measured as 2-d radicle protrusion (R2) and to standard germination (SG, normal seedlings). Color development was insensitive to variations in seed pesticide treatments, sample size (1-4 g), incubation temperature (19-26°C), incubation period (24-30 h), and initial seed moisture (5%-10%). The test partitioned seed samples into deteriorated and non-deteriorated categories for hybrid, open-pollinated, B. napus and B. rapa seeds with 84%–100% accuracy. The test was 86% accurate at classifying samples by R2 and 70% accurate at classifying sample by SG. Precision of repeat determinations was sufficient to permit single assays. Although further study is required, the assay appears to have promise as a practical on-farm seed vigor test.