Monitoring of plant water uptake by measuring root dielectric properties on a fine timescale: diurnal changes and response to leaf excision.

BACKGROUND: The measurement of root dielectric response is a useful non-destructive method to evaluate root growth and function. Previous studies tracked root development throughout the plant growing cycle by single-time electrical measurements taken repeatedly. However, it is known that root conductivity and uptake activity can change rapidly, coupled with the day/night cycles of photosynthetic and transpiration rate. Therefore, the low-frequency dielectric monitoring of intact root-substrate systems at minute-scale temporal resolution was tested using a customized impedance measurement system in a laboratory environment. Electrical capacitance (CR) and conductance (GR) and the dissipation factor (DR) were detected for 144 h in potted maize, cucumber and pea grown under various light/dark and temperature conditions, or subjected to progressive leaf excision or decapitation. Photosynthetic parameters and stomatal conductance were also measured to evaluate the stress response. RESULTS: The CR and GR data series showed significant 24-h seasonality associated with the light/dark and temperature cycles applied. This was attributed to the diurnal patterns in whole-plant transpiration (detected via stomatal conductance), which is strongly linked to the root water uptake rate. CR and GR decreased during the 6-day dark treatment, and dropped proportionally with increasing defoliation levels, likely due to the loss of canopy transpiration caused by dark-induced senescence or removal of leaves. DR showed a decreasing trend for plants exposed to 6-day darkness, whereas it was increased markedly by decapitation, indicating altered root membrane structure and permeability, and a modified ratio of apoplastic to cell-to-cell water and current pathways. CONCLUSIONS: Dynamic, in situ impedance measurement of the intact root system was an efficient way of following integrated root water uptake, including diurnal cycles, and stress-induced changes. It was also demonstrated that the dielectric response mainly originated from root tissue polarization and current conduction, and was influenced by the actual physiological activity of the root system. Dielectric measurement on fine timescale, as a diagnostic tool for monitoring root physiological status and environmental response, deserves future attention.

[Analysis of associations between mortality and biological and social-economic individual determinants]. / A halandóságot befolyásoló egyéni biológiai és társadalmi-gazdasági tényezok hatásrendszerének vizsgálata.

Health impact assessment is an internationally recognized tool for informed decision-making. The authors participated in building statistical models for assessing the health effects of decisions made inside and outside the health sector. They used logistic regression to investigate the role of individual factors like gender, age, education and economic activity determining the all-cause mortality and diseases of circulatory system and neoplasm as well. The results of statistical modelling proved that gender, education and economic activity modify the effect of age on mortality in multiple interactions. Since several factors have impact simultaneously on mortality, modifying the others' effects, analyzing these associations only by use of multivariate statistical methods is an adequate approach. Models presented in this article can be starting points for investigations exploring the effects of multiple health-determinants and researches in which also social-economic determinants are included in health impact assessment.