Effects of severe water stress on partitioning of 14C-assimilates in tomato plants

Tomato plants (Lycopersicon esculentum Mill. cv Nikita) were grown hydroponically and subjected to severe water stress induced by addition of PEG-6000 to the nutrient solution. The PEG-treatment clearly impaired growth. Leaf photosynthesis decreased during the experiment. Moreover, the decrease in photosynthesis was associated with a decrease in dry weight of the shoot compared to the root. Also leaf area expansion, stomatal conductance and transpiration decreased. Water stress enhanced the transport of 14C-assimilates from the source leaf to the lower parts of the plant where the assimilates were incorporated in the lower stem, the leaves below the source leaf and the roots. It was observed that 14C was much more concentrated in the roots compared to the other plant parts

Drought and the diurnal patterns of stem CO2 efflux and xylem CO2 concentration in young oak (Quercus robur)

A young potted oak (Quercus robur L.) tree was subjected to drought by interrupting the water supply for 9 days. The tree was placed in a growth chamber in which daily patterns of temperature and radiation were constant. The effects of drought on the water and carbon status of the stem were examined by measuring stem sap flow rate, stem water potential, stem diameter variations, stem CO2 efflux rate (F-CO2) and xylem CO2 concentration ([CO*(2)]). Before and after the drought treatment, diurnal fluctuations in Fco, and [CO*(2)] corresponded well with variations in stem temperature (T,,,). Daytime depressions in F-CO2 did not occur. During the drought treatment, F-CO2 still responded to stepwise changes in temperature, but diurnal fluctuations in F-CO2 were no longer correlated with diurnal fluctuations in T, From the moment daily growth rate of the stem became zero, diurnal fluctuations in F-CO2 became closely correlated with diameter variations, exhibiting clear daytime depressions. The depressions in F-CO2 were likely the result of a reduction in metabolic activity caused by the lowered daytime stem water status. Xylem [CO*(2)] showed clear daytime depressions in response to drought. When the tree was re-watered, F-CO2 and [CO*(2)] exhibited sharp increases, coinciding with an increase in stem diameter. After resumption of the water supply, daytime depressions in FCO2 and [CO*(2)] disappeared and diurnal fluctuations in F-CO2 and [CO*(2)] corresponded again with variations in T-st

What Are They Doing Anyway?: Library as Place and Student Use of a University Library

Objective - To determine student use of library spaces, the authors recorded student location and behaviors within the Library, to inform future space design. Methods - The case study method was used with both quantitative and qualitative measures. The authors had two objectives to guide this assessment of library spaces: 1) To determine what library spaces are being used by students and whether students are working individually, communally, or collaboratively and 2) To determine whether students use these spaces for learning activities and/or social engagement. Results - After data collection and analysis, the authors determined students are using individual or communal spaces almost equally as compared with collaborative group spaces. Data also revealed peak area usage and times. Conclusion - Observed student individual and social work habits indicate further need for spaces with ample electrical outlets and moveable tables. Further study is recommended to see whether additional seating and renovated spaces continue to enhance informal learning communities at URI and whether the Library is becoming a “third place” on campus

Fantastique et la science-fiction en France, en Estonie et en Finlande (19 et 20 novembre 2010, Institut finlandais, Paris)

Les 19 et 20 novembre 2010, le colloque Le fantastique et la science-fiction en France, en Estonie et en Finlande s’est tenu à l’Institut finlandais à Paris. Organisé par les sections d’estonien et de finnois de l’INALCO, le Centre d’étude de l’Europe médiane (CEEM – INALCO), l’Institut finlandais et le CIEH&CIEFi Sorbonne nou­velle, il a rassemblé chercheurs, professionnels et passionnés, venus des trois pays concernés. Ce colloque était présidé par Martin Carayol, doctorant à l’INALCO, et K..

Supporting dune management by quantitative estimation of evapotranspiration

Research was conducted in the nature reserve De Westhoek (B) in order to estimate the hydrological impact of shrub removal in favour of the recolonisation and development of herbaceous vegetation types in the dune slacks. Dune slacks are one of the most rare ecotopes in Europe. Therefore, the evapotranspiration of herbaceous and shrub vegetation types was estimated based on experimentally obtained data and modelling. Analysis of the experimentally obtained stomatal resistance values revealed that there was no difference in the minimal stomatal resistance values (in absence of any stress) between herbs and shrubs. Stomatal resistance was modelled based as a function of climatic variables. Maximal rooting depth was similar in both vegetation types, and was maximal 60cm. For both vegetation types more than 60% of the roots were found in the upper 15cm. The mean leaf-area-index (LAI) of herbaceous and shrub vegetations is respectively 2.11±0.34 and 3.27±0.20 m2.m-2. Evapotranspiration of both vegetation types was modelled with a multi-layer dynamic vegetation model FORUG and seasonal evapotranspiration amounted roughly 200 and 550mm for the herbaceous and shrub vegetation types respectively. Although these estimates can be somewhat refined, from these results it can be concluded that shrub removal, and the replacement of this vegetation type by a herbaceous vegetation type, will not result in a lowering of the groundwater table. This knowledge can help managing hydrologically disturbed dune ecosystems

Measurement and simulation of the ventilation rates in a naturally ventilated Azrom type greenhouse in Zimbabwe

A simple greenhouse ventilation model, based on the stack and wind effects (the main driving forces for natural ventilation) was adapted, calibrated and validated using measured air renewal rates in a three span naturally ventilated Azrom type greenhouse in Zimbabwe. Crop transpiration rates were monitored using stem heat balance sap flow gauges installed on the main stems of rose plants to continuously monitor whole-plant transpiration (WPT). This allowed continuous and automatic determination of full scale air renewal and leakage rates using the water vapour balance method. The model was fitted to experimental data of ventilation rates, and discharge and wind effect coefficients were determined. The results show a good fit between measured and predicted values (R2 = 0.80 and 0.82 for winter and summer, respectively), although there is a general over-estimation of the greenhouse air renewal rates, particularly during the night. The model, nevertheless, adequately describes the natural ventilation process in the greenhouse all year round. The model can be used as a design tool to evaluate and optimise the effects of different ventilation configurations and strategies on greenhouse air renewal rates, and as a component in a greenhouse climate model in order to further evaluate the effects of ventilation strategies on the inside greenhouse and crop microclimate, and thus lead to better greenhouse climate control