Led induced chlorophyll fluorescence transient imager for measurements of health and stress status of whole plants

We have developed LED (light emitting diode) induced fluorescence transient imaging instrumentation to image the plant health/stress status by calculation of two images: Fv/Fm (variable fluorescence over saturation level of fluorescence) and the time response, tTR, of the fluorescence time curve. Within a short time interval (˜580 ms) multiple images (typically 20) are captured using the LEDs in the pulsed mode. For each pixel of the fluorescence image Fv/Fm and tTR are calculated and presented as images that correlate with the quantum yield of PSII photochemistry and the time response of this process, respectively. The advantage of the technology lies in the imaging of photosynthetic parameters within a short time interval, remotely and under light conditions. This was accomplished by the development of a high intensity pulsed LED light source (total 5 kW electrical power) and using the LEDs in the pulsed mode with a pulse width of 15 ms and time between sequential pulses of 14 ms. Using this instrumentation we investigated the effect of herbicide treatment, Sencor, on black nightshade (Solanum nigrum L.) plants. Effects of the herbicide on the first fluorescence images could be detected. At the saturation level of the fluorescence this effect disappeared. The effect of the herbicide was visualized on the Fv/Fm image and the time response tTR image. Healthy and herbicide treated parts of the plant yielded average values of Fv/Fm=0.81±0.03 and 0.06±0.02, respectively. Furthermore, the effect of drought stress was investigated on saintpaulia (Saintpaulia ionantha) plants. Under dark conditions no differences in the image of Fv/Fm and tTR could be detected between the control and the plant with drought stress. Under actinic light of 90 µmol m-2 s-1 differences were observed in images of (Fm’-F’)/Fm’ and tTR’. We conclude that for the first time images of a time response of the photosynthesis of leaves are presented. Furthermore, the proposed instrumentation can be used for high throughput screening, as a sensor in sorting machines and has potential greenhouse applications

Mogelijkheden om vroeg tijdig bladrandproblemen te signaleren met MIPS bij Hortensia

Met geavanceerde camera technieken zijn beelden vast te leggen van fotosynthese activiteit en het is ook mogelijk gebleken om bladgedeelten met stress vast te leggen, zonder dat deze stress met het blote oog al te zien is. Dit opent perspectieven om monitorringonderzoek te doen naar het ontstaan van bladrandschade en tegelijkertijd naar de eventuele mogelijkheden tot ingrijpen met (wellicht) herstel. Deze metingen worden in het donker uitgevoerd. Er is recentelijk een nieuwe camera ontwikkeld die ook in het licht kan meten, maar bij een meting in het licht zal het verschil tussen schade- en gezonde plekken waarschijnlijk kleiner zijn dan bij een meting in het donker. Dit laatste zal getest moeten worden

Production of organic seeds: Status, Challenges and Prospects

General article on the requirements of organic agriculture for seed production. Beside this the organic agricultural system has other demands for organic seed since it does not use chemical control measures and uses natural fertilizers instead of chemical fertilizers. Research can offer an important contribution in the production of seed without diseases

Waterberging en natuur in het beekdal van de Beerze : veldwerkplaats Beekdallandschap Boxtel, 30 juni 2008

Beekdalen zijn heel geschikt om tijdelijk overtollig water op te slaan, om het vervolgens geleidelijk te laten afvloeien. Daarom worden vele beekdalen voor dit doel heringericht. Tegelijkertijd zijn de beekdalen echter vaak onderdeel van Natura 2000 of de EHS en daar gelden dus natuurdoelen. Zo ook het beekdal van de Beerze. De beek is op veel plaatsen verondiept, versmald, van vistrappen voorzien, meandert weer en een deel van het beekdal doet dienst als waterberging. Maar door de waterberging van het voedselrijke en soms verontreinigde water lukt het veelal niet de natuurdoelen te behalen. Zo’n situatie komt op veel meer plaatsen in Nederland voor. In dit verslag de ervaringen van Boxtel

A new lab facility for measuring bidirectional reflectance/emittance distribution functions of soils and canopies

Recently, a laboratory measurement facility has been realized for assessing the anisotropic reflectance and emittance behaviour of soils, leaves and small canopies under controlled illumination conditions. The facility consists of an ASD FieldSpec 3 spectroradiometer covering the spectral range from 350 – 2500 nm at 1 nm spectral sampling interval. The spectroradiometer is deployed using a fiber optic cable with either a 1°, 8° or 25° instantaneous field of view (IFOV). These measurements can be used to assess the plant pigment (chlorophyll, xanthophyll, etc.) and non-pigment system (water, cellulose, lignin, nitrogen, etc.). The thermal emittance is measured using a NEC TH9100 Infrared Thermal Imager. It operates in a single band covering the spectral range from 8 – 14 mm with a resolution of 0.02 K. Images are 320 (H) by 240 (V) pixels with an IFOV of 1.2 mrad. A 1000 W Quartz Tungsten Halogen (QTH) lamp is used as illumination source, approximating the radiance distribution of the sun. This one is put at a fixed position during a measurement session. Multi-angular measurements are achieved by using a robotic positioning system allowing to perform either reflectance or emittance measurements over almost a complete hemisphere. The hemisphere can be sampled continuously between 0° and 80° from nadir and up to a few degrees from the hot-spot configuration (depending on the IFOV of the measurement device) for a backscattering target. Measurement distance to targets can be varied between 0.25 and 1 m, although with a distance of more than 0.6 m it is not possible to cover the full hemisphere. The goal is to infer the BRDF (bidirectional reflectance distribution function) and BTDF (bidirectional thermal distribution function) from these multi-angular measurements for various surface types (like soils, agricultural crops, small tree canopies and artificial objects) and surface roughness. The steering of the robotic arm and the reading of the spectroradiometer and the thermal camera are all fully automated

The need for a supply of high quality organic vegetable seeds

Production of high quality organic vegetable seeds encounters several challenges. Research is performed to support seed companies in producing vigorous and healthy organic vegetable seeds. Examples are provided with respect to research on seed vigour, determining critical control points to avoid disease transmission to the seeds, seed treatments with natu-ral compounds, new seed sorting techniques and enhancement of the natural plant defence. It is noticed that the restrictions in EU regulation 2092/91 on organic production are at present blocking the use of promising natural and sustainable components for seed treatments

Improvement of the quality of propagation material for organic farming system

The use of organic propagation material is obligatory according to the current EU regulations for organic production. However, frequently difficulties are en-countered regarding the availability, the costs or the quality. In the Netherlands a national research program aims at developing solutions, needed for improving the production of high quality organic propagation material. The main emphasis in the pro-gram is on the model crops cabbage, onion, wheat and potato. Individual projects within the program include epidemiological studies of seed borne dis-eases to develop disease prevention strategies, meth-ods to improve resistance of seeds and seedlings towards pathogens and methods to control silver scurf in seed potatoes, development of multi-spectral analysis and sorting techniques and methods for analysis and improvement of seed vigour. Active involvement of producers and users of the seeds or seed potatoes ensures that the results will be imple-mented in practice. The program also aims at strengthening the international collaboration, amongst others through involvement in international research projects