Fruit and Leaf Sensing for Continuous Detection of Nectarine Water Status

Continuous assessment of plant water status indicators might provide the most precise information for irrigation management and automation, as plants represent an interface between soil and atmosphere. This study investigates the relationship of plant water status to continuous fruit diameter (FD) and inverse leaf turgor pressure rates (pp) in nectarine trees [Prunus persica (L.) Batsch] throughout fruit development. The influence of deficit irrigation treatments on stem (Ψstem) and leaf water potential, leaf relative water content, leaf hydraulic conductance and fruit growth was studied across the stages of double-sigmoidal fruit development in 'September Bright' nectarines. Fruit relative growth rate (RGR) and leaf pressure change rate (RPCR) were derived from FD and pp to represent rates of water in- and outflows in the organs, respectively. Continuous RGR and RPCR dynamics were independently and combinedly related to plant water status and environmental variables. The independent use of RGR and RPCR yielded significant associations with midday Ψstem, the most representative index of tree water status in anisohydric species. However, the combined use of nocturnal fruit and leaf parameters unveiled an even more significant relationship with Ψstem, suggesting a different fruit-to-leaf water balance in response to pronounced water deficit. In conclusion, we highlight the suitability of a multi-organ sensing approach for improved prediction of tree water status

How does the WFD address cumulative stress (including mixture toxicity) of pollutants to achieve good chemiscal and ecological status of water bodies?

It is now more than ten years ago that the Water Framework Directive (WFD) was adopted by the European Parliament. The main objectives of the WFD are (i) to achieve good ecological and chemical status for inland surface waters, transitional waters and coastal waters in EU Member States, (ii) to assess the ecological and chemical status of these water bodies by means of monitoring programmes, and (iii) to implement programmes of measures to reduce environmental stress to an acceptable level. By adopting the WFD a fundamental change in management objective was introduced in the European Union, from merely pollution control to ensuring ecosystem integrity as a whole [1]. The ecological status of WFD water bodies is assessed by monitoring of biological quality elements (e.g. fish, macroinvertebrates, macrophytes, benthic diatoms, phytoplankton), general chemical and physico-chemical quality elements (e.g. pH, alkalinity, nutrients) and hydromorphological quality elements. These quality elements monitored in water bodies are compared with the status of more or less pristine reference ecosystems. If in WFD water bodies the ecological status deviates too much from the reference condition action is needed for achieving the acceptable ecological status. The chemical status of water bodies is assessed by comparing chemical monitoring data with Environmental Quality Standards (EQS) for priority (hazardous) substances and other relevant substances. Currently, 41 priority (hazardous) substances are listed in the European Union, but a regular update of this list with emerging substances is anticipated. If in water bodies exposure concentrations of one or more of these priority (hazardous) substances are not in compliance with the officially published EQS’s for these pollutants a good chemical status is not reached and action is needed to improve this. In contrast to the EU-level priority (hazardous) substances the other relevant substances are river basin or Member State specific. These other relevant substances have been selected because they are believed to potentially impair the ecological status of specific WFD water bodies and/or related human health aspects. The methodology to derive the EQS’s for other relevant substances is similar to that of the priority (hazardous) substances. This methodology is described in the new Technical Guidance Document for deriving Environmental Quality Standards (will be officially released in 2011). In European river basins the priority (hazardous) substances and river specific pollutants have to be measured on a regular basis. Under the umbrella of the WFD, EQS derivation is primarily based on a single substance toxicity assessment approach. In exceptional cases EQS’s for mixtures may be derived when their qualitative and quantitative composition is well-defined and/or well described (e.g. biocide preparations, PCB’s, dioxins). The concentration addition (CA) concept is used as a default when setting EQS’s for mixtures. Although compliance with good chemical status is primarily based on EQS’s for individual substances, cumulative stress (including mixtures) of toxicants may be identified as a main pressure affecting ecological status. In that case the cumulative risks caused by pollutants have to be reduced

Putting two water transport models to the test under wet and dry conditions

In order to improve fruit quality and quantity, accurate monitoring of the water status is necessary. The water status can be continuously predicted by using a mechanistic water transport and storage model (e.g. Steppe et al., 2006; 2008). This model typically links measurements of sap flow rate (SF) and stem diameter variations (D) to simulate stem water potential (Ψstem), which is recognised as one of the best indicators for evaluating plant water status. Despite good model performance under sufficient water availability, the model fails under dry conditions. However, a proper simulation of water transport under drought is essential for many applications. For example, grapevines are often subjected to some level of drought stress during the growing season in order to improve the quality of the grapes. Therefore, we aim at adjusting the existing model to improve its performance in simulating water transport during drought conditions. First, a dynamic function describing changes in hydraulic xylem resistance is used to replace the former constant parameter, and represents the resistances encountered in the soil, root and stem (RX). Second, also the former constant radial flow resistance between xylem and storage tissues has been replaced by an equation (RS). For the first time, equations for RX and RS instead of parameters were used in the model, and simulations were compared to the original ones. Both models functioned well under wet conditions, but where the original model failed under dry events, the adapted model could still accurately simulate D and Ψstem under these conditions. The adapted model is thus capable of describing the grapevine’s hydraulic response to both wet and (severe) drought conditions and seems very promising within the context of an automatic plant-based system for water status monitoring

Relationships between water status, leaf chlorophyll content and photosynthetic performance in Tempranillo vineyards

Producción CientíficaThe aims of this work were (i) to study the relationships between leaf water potential, foliar chlorophyllcontent and photosynthetic performance of grapevines under field conditions, and (ii) to evaluate thefeasibility of chlorophyll fluorescence parameters to assess water status in commercial vineyards. Duringthree consecutive seasons (2011 to 2013), 20 non-irrigated “Tempranillo” vineyard subzones were monitoredin Ribera del Duero, Spain. Data on foliar chlorophyll content, midday and predawn leaf water potential,net assimilation and chlorophyll fluorescence parameters were measured at fruit set, pre-véraison andvéraison. The results show that the water potential indicated weak to moderate stress in the study yearsand decreased along the vegetative cycle, while foliar chlorophyll contents showed an increasing trend. Thecorrelation between both variables was not consistent. Linear regression of the chlorophyll fluorescenceparameters in dark-adapted leaves, Fo, Fv and Fv/Fm, over chlorophyll content was strong in all thestudy years (higher determination coefficients for Fv/Fm at fruit set in 2012 and 2013). In general, thewater potential with low coefficients of variation showed a low effect on photosynthesis activity, althoughvalues in variables such as Fm, Fv, Fv/Fm, Fs/Fo and ΦPSII registered an increasing trend when middayleaf water potential decreased in the pre-véraison and véraison stages. These variables could be useful toestimate water status in commercial vineyards for application in precision viticulture.Ministerio de Economía, Industria y Competitividad (Project RTA2014- 00077-C02-02)Junta de Castilla y León (Project VA011A10-2)

Water Retention, Bulk Density, Particle Size, and Thermal and Hydraulic Conductivity of Arable Soils in Interior Alaska

The relative proportion of liquid, gas, and solid as constituents of soil depends on factors such as climate, biological activity, and management practices. Therefore, the physical state of soil is a dynamic process, changing with time and position in the profile. Temperature, thermal and hydraulic conductivity, density, and water content are some quantitative properties characterizing the physical state of soil. These properties are important in describing soil processes such as water and heat flow, movement of chemicals, biological activity, and erosion. Water in the soil is subject to a number of forces resulting from the attraction of the soil matrix for water and presence of solutes and gravity. The energy status of water-the sum of these forces-is termed water potential. Processes such as evaporation and plant water uptake are governed by the gradient in water potential in the soil and across the root-soil interface, respectively. The term water potential is more descriptive of the soil water status than water content as movement of water is in response to differences in water potential

Comparing Welfare Estimates from Fixed Status Quo Attributes vs People’s Perceived Attributes of Water Quality

Data from a choice experiment on the community’s preferences for water quality improvements in streams was used to assess the effect of using a fixed status quo versus people’s perceived status quo on willingness to pay values. More than 50% of respondents perceived the quality of water in streams to be different to the status quo in the initial experimental design. Study results have shown that respondents who opted for their own perceived status quo alternative had stronger preferences and higher willing to pay for water quality improvements than their counterparts.Choice experiments, Fixed status quo, People’s perceived status quo, Willingness to pay, Agricultural and Food Policy, Community/Rural/Urban Development, Crop Production/Industries, Environmental Economics and Policy, Farm Management, Health Economics and Policy, Land Economics/Use,

The effects of water quality on freshwater fish populations - final report

There is a need to determine quantitative relationships between fishery status and water quality in order to make informed judgements concerning fishery health and the setting of environmental quality standards for fishery protection. Such relationships would also assist in the formulation of a system for classifying fisheries. A national database of fisheries and water quality has been collated from the archives of pollution control authorities throughout the UK. A number of probable and potential water quality effects on fish populations have been identified from a thorough analysis of the database, notwithstanding large confounding effects such as habitat variation and fish mobility, and the generally sparse nature of water quality information. A number of different approaches to data analysis was utilised, and the value of each has been appraised. Recommendations concerning the integration of water quality assessment approaches have been made and further research on fishery status, and its measurement, in relation to water quality has been suggested

Effect of stem age on the response of stem diameter variations to plant water status in tomato

Plant water status plays a major role in glasshouse cultivation of tomato (Solanum lycopersicum L.). New climate control technologies alter the glasshouse climate and make it less dependent on solar radiation. However, irrigation strategies are still often based on solar radiation sums. In order to maintain a good plant water status, it is interesting to use plant-based methods such as monitoring sap flow (F) or stem diameter variations (SDV). Though SDV give important information about plant water status, an unambiguous interpretation might be difficult because other factors such as stem age, fruit load and sugar content of the stem also affect SDV. In this study, an analysis of the effect of stem age on the response of SDV to water status was performed by calibration of a mechanistic flow and storage model. This allowed us to determine how parameter values changed across the growing season. Tissue extensibility decreased over the growing season resulting in a lower growth rate potential, whereas daily cycles of shrinking and swelling of the stem became more pronounced towards the end of the growing season. Parameters were then adapted to time-dependent variables and implemented in the model, allowing long term simulation and interpretation of SDV. Sensitivity analysis showed that model predictions were very sensitive to initial sucrose content of the phloem tissue and the parameters related to plastic growth