Imaging planted in photosynthesis research

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Heinz Walz of Effeltrich, Germany has developed a fluorometer using machine vision cameras that can determine the intensity of photosynthesis in plants quickly and accurately.

The device aims to answers questions of how plants react to climate change, disease, and to discern the best ways to achieve environmental stability. The amount of photosynthesis can be used as an indicator of the plants physiological condition.

By measuring the fluorescent energy loss during the process of photosynthesis from the chlorophyll, the photosynthetic activity can be measured in a non-destructive and more accurate way. Previous techniques measured the amount of chlorophyll – the part of the leaf cell that performs the photosynthesis – within the leaf; however this can be misrepresentative of the photosynthetic activity of the leaf.

Oliver Meyerhoff, a scientist with Walz, explained: ‘Fluorescence yield varies from location to location, which allows for conclusions about photosynthetic efficiency and with it the vitality of the sample being measured.’ This means the fluorometer is applicable to a range of research disciplines – from the basic physiology of higher and lower plants, coral research, or marine ecophysiology.

The system consists of a measuring head with integrated special lighting and a digital camera from Allied Vision Technologies. Samples of different sizes can be installed in the measuring head, depending upon the model. Here, samples are protected from outside light and are illuminated with precise light pulses. Blue or red high-power LEDs whose spectra have been calibrated to the absorption characteristics of chlorophyll function as the light source.

The fluorescence levels are measured using a camera from Allied Vision Technologies. The plant samples are stimulated with both minimal intensity light that cannot trigger photosynthesis and strong light pulses, up to ten times the intensity of sunlight. In this manner, the number of active centres in the sample can be determined. ‘Following these two first steps, we know how the plant behaves in darkness and in maximum light,’ Meyerhoff explained. ‘After this calibration, we can combine measurements with different illuminations and interpret the values.’

The images captured by the camera are then displayed and analysed by the ImagingWin Software from Walz. The values are graphically represented using a colour scale in an image. Eighteen different parameters can be played back in different colour palettes.

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