Early detection of Psa infection in kiwifruit by means of infrared thermography at leaf and orchard scale

© CSIRO 2014. Pseudomonas syringae pv. actinidiae (Psa), the causal agent of bacterial canker of kiwifruit, has become a worldwide threat for the kiwifruit industry. In this work, the potential of infrared thermography for early detection of physiological symptoms related to Psa-infection at leaf and at orchard block scale was assessed. At the leaf level, thermal cold spots appeared shortly after Psa-infection, well before any visual symptoms. A few weeks after infection, thermal hot spots were observed, associated with, but not limited to, spots of visible leaf necrosis. At orchard block level, Psa-infected canes were significantly warmer in both blocks and on all measurement days. A novel wet reference surface, existing of a cluster of cotton imitation leaves with similar dimensions and orientation as real leaves and remaining wet through sucking up water from a small container, was used to estimate the crop water stress index (CWSI). CWSI showed stable values of infected and uninfected areas during the day and between following days. Crop temperature and CWSI were closely correlated with leaf stomatal conductance, which was lower in infected canes. A Psa-infection map based on canopy temperature revealed that Psa infects the outer canes rather than the central part of the canopy

A new wet reference target method for continuous infrared thermography of vegetations

© 2016 Elsevier B.V.. Although infrared thermography for stress detection in plants is popular in scientific research, it is rarely used in continuous and automated applications. One of the main reasons for this is that the most precise method for generating wet reference targets, used for normalizing the leaf or canopy surface temperature for microclimatic conditions, requires manual wetting before each image capture. In this article, we present and evaluate a new type of wet reference target that remains wet while having an energy balance as similar as possible to that of the canopy. This reference target consists of a cloth knitted around a solid frame whose shape and dimensions mimic those of the leaves. The cloth remains wet by constantly absorbing water from a reservoir. The new reference target was evaluated on grapevine and kiwifruit plants in greenhouse and orchard conditions. In greenhouse conditions, measured stomatal conductance was consistently more highly correlated with the stomatal conductance index Ig when Ig was calculated with the new wet reference rather than the manually wetted reference target. Furthermore, the temperature difference between leaves and the new reference target remained stable for as long as measured, in contrast with the manually wetted leaves. Ig obtained with the new reference target method was also highly correlated with stomatal conductance (gs) of both crops in orchard conditions. A new empirical regression model to estimate gs from Ig in greenhouse conditions was introduced and evaluated. This regression model incorporates the background temperature, a parameter that needs to be included in thermographic measurements for obtaining correct surface temperatures, thus avoiding the need for any additional measurements. The same regression model can be applied on different days with differing conditions. The model performed better than other tested empirical models and provided unbiased estimates of gs on days with different conditions, resulting in a root mean square error of 22-25% of gs. Thus, it provides a promising method for continuous remote sensing of stomatal conductance or drought stress detection of plants and vegetations

A mechanistic model to predict distribution of carbon among multiple sinks.

International audienceFor over 35 years, biological scientists have come to rely on the research protocols and methodologies in the critically acclaimed Methods in Molecular Biology series. The series was the first to introduce the step-by-step protocols approach that has become the standard in all biomedical protocol publishing. Each protocol is provided in readily-reproducible step-by-step fashion, opening with an introductory overview, a list of the materials and reagents needed to complete the experiment, and followed by a detailed procedure that is supported with a helpful notes section offering tips and tricks of the trade as well as troubleshooting advice. These hallmark features were introduced by series editor Dr. John Walker and constitute the key ingredient in each and every volume of the Methods in Molecular Biology series. Tested and trusted, comprehensive and reliable, all protocols from the series are indexed in PubMed

Exploring the transport of plant metabolites using positron emitting radiotracers

Short-lived positron-emitting radiotracer techniques provide time-dependent data that are critical for developing models of metabolite transport and resource distribution in plants and their microenvironments. Until recently these techniques were applied to measure radiotracer accumulation in coarse regions along transport pathways. The recent application of positron emission tomography (PET) techniques to plant research allows for detailed quantification of real-time metabolite dynamics on previously unexplored spatial scales. PET provides dynamic information with millimeter-scale resolution on labeled carbon, nitrogen, and water transport over a small plant-size field of view. Because details at the millimeter scale may not be required for all regions of interest, hybrid detection systems that combine high-resolution imaging with other radiotracer counting technologies offer the versatility needed to pursue wide-ranging plant physiological and ecological research. In this perspective we describe a recently developed hybrid detection system at Duke University that provides researchers with the flexibility required to carry out measurements of the dynamic responses of whole plants to environmental change using short-lived radiotracers. Following a brief historical development of radiotracer applications to plant research, the role of radiotracers is presented in the context of various applications at the leaf to the whole-plant level that integrates cellular and subcellular signals and∕or controls