In vitro root induction by 24-epibrassinolide on hypocotyl segments of soybean [Glycine max (L.) Merr.]

Soybean hypocotyl segments were treated in the dark with 24-epibrassinolide (BR) at a range of concentrations for different durations. The maximum effect on adventitious root induction, both in terms of number and length was obtained at very low concentration (0.0001 ppm) of BR applied for 8 h. Higher concentrations were supraoptimal unless applied for a shorter period (4 h). BR was ineffective when applied at low concentration in continuous light.     

Indol-3yl-acetic acid in roots of Zea mays

Indol-3yl-acetic acid was identified in extracts of sterile roots of Zeamays seedlings by means of TLC, chromogenic reactions, GLC and GC-MS.     

Genotypic variation in seedling root architectural traits and implications for drought adaptation in wheat (Triticum aestivum L.)

Root system characteristics are of fundamental importance to soil exploration and below-ground resource acquisition. Root architectural traits determine the in situ space-filling properties of a root system or root architecture. The growth angle of root axes is a principal component of root system architecture that has been strongly associated with acquisition efficiency in many crop species. The aims of this study were to examine the extent of genotypic variability for the growth angle and number of seminal roots in 27 current Australian and 3 CIMMYT wheat (Triticum aestivum L.) genotypes, and to quantify using fractal analysis the root system architecture of a subset of wheat genotypes contrasting in drought tolerance and seminal root characteristics. The growth angle and number of seminal roots showed significant genotypic variation among the wheat genotypes with values ranging from 36 to 56 (degrees) and 3 to 5 (plant⁻¹), respectively. Cluster analysis of wheat genotypes based on similarity in their seminal root characteristics resulted in four groups. The group composition reflected to some extent the genetic background and environmental adaptation of genotypes. Wheat cultivars grown widely in the Mediterranean environments of southern and western Australia generally had wider growth angle and lower number of seminal axes. In contrast, cultivars with superior performance on deep clay soils in the northern cropping region, such as SeriM82, Baxter, Babax, and Dharwar Dry exhibited a narrower angle of seminal axes. The wheat genotypes also showed significant variation in fractal dimension (D). The D values calculated for the individual segments of each root system suggested that, compared to the standard cultivar Hartog, the drought-tolerant genotypes adapted to the northern region tended to distribute relatively more roots in the soil volume directly underneath the plant. These findings suggest that wheat root system architecture is closely linked to the angle of seminal root axes at the seedling stage. The implications of genotypic variation in the seminal root characteristics and fractal dimension for specific adaptation to drought environment types are discussed with emphasis on the possible exploitation of root architectural traits in breeding for improved wheat cultivars for water-limited environments.     

Transpiration difference under high evaporative demand in chickpea (Cicer arietinum L.) may be explained by differences in the water transport pathway in the root cylinder

• Terminal drought substantially reduces chickpea yield. Reducing water use at vegetative stage by reducing transpiration under high vapor pressure deficit (VPD), i.e. under dry/hot conditions, contributes to drought adaptation. We hypothesized that this trait could relate to differences in a genotype's dependence on root water transport pathways and hydraulics.
• Transpiration rate responses in conservative and profligate chickpea genotypes were evaluated under increasing VPD in the presence/absence of apoplastic and cell‐to‐cell transport inhibitors.
• Conservative genotypes ICC 4958 and ICC 8058 restricted transpiration under high VPD compared to the profligate genotypes ICC 14799 and ICC 867. Profligate genotypes were more affected by aquaporin inhibition of the cell‐to‐cell pathway than conservative genotypes, as measured by the root hydraulic conductance and transpiration under high VPD. Aquaporin inhibitor treatment also led to a larger reduction in root hydraulic conductivity in profligate than in conservative genotypes. In contrast, blockage of the apoplastic pathway in roots decreased transpiration more in conservative than in profligate genotypes. Interestingly, conservative genotypes had high early vigour, whereas profligate genotypes had low early vigour.
• In conclusion, profligate genotypes depend more on the cell‐to‐cell pathway, which might explain their higher root hydraulic conductivity, whereas water‐saving by restricting transpiration led to higher dependence on the apoplastic pathway. This opens the possibility to screen for conservative or profligate chickpea phenotypes using inhibitors, itself opening to the search of the genetic basis of these differences.

     

Hormonal factors controlling the initiation and development of lateral roots

As the first part of a comprehensive study of the hormonal control of lateral root initiation and development, the effect of surgical treatments such as removal of the root tip, one or more cotyledons, the young epicotyl, or combination of these treatments, on the induction and emergence of lateral roots on the primary root of pea seedlings has been examined. Results show that removal of the root tip leads to a rapid but transitory increase in the number of lateral primordia, the largest number arising in the most apical segment of decapitated roots suggesting the accumulation of acropetally moving promoter substances in this region. The cotyledons appear to be the main source of promoter substances for both the induction and emergence of lateral roots, although one or more promoters also appear to be produced in the epicotyl. The data further indicate that the root tip is possibly the source of a substance which moves basipetally and interacts with acropetally moving promoters to regulate the zone for lateral primordia initiation; the root tip also appears to be the source of a powerful inhibitor of lateral root emergence.     

Anwendung der automatisierten Festphasenextraktion bei der Bestimmung von Ochratoxin A

For some foodstuffs, determination of the mycotoxin ochratoxin A (OTA) requires time consuming clean up by means of solid phase extraction (SPE). Therefore a system for automated SPE was tested for cleaning up roasted coffee as a possible way of shortening preparation time. Validation of the method in accordance to the so called “Concept '98” led to a LOD of 0.2 μg/kg and a recovery rate of 92%. By using the described procedure with samples of roasted coffee the OTA contents varied between the LOD and 3.4 μg/kg. This method was also used to determine ochratoxin A in liquorice roots, ginger and valerian.

Presented at the 26^th Mykotoxin Workshop in Herrsching, Germany, May 17–19, 2004