Wageningen UR Greenhouse Horticulture has developed a new camera that can much faster than existing equipment measure the effect of a stress factor on photosynthesis. Patent on the technique has been applied for and the camera is now ready for further introduction. There are lots of practical uses.
Photosynthesis of a plant under stress is sub-optimal. Too low temperatures or a Botrytis infestation, e.g., immediately affect photosynthesis. This means that photosynthesis measurements can provide information on the condition of the plant. With existing photosynthesis measuring equipment it is not possible to check the whole plant. And measurements are slow and therefore not suitable for large-scale use under practical greenhouse conditions.
After ten years of research and development Wageningen UR Greenhouse Horticulture is introducing a new technique that measures photosynthesis of the total plant. This technique is based on measurement of the so-called light response curve. The technique is now under further development to make the camera sufficiently robust for use in greenhouse practice.
Unique measurement
Photosynthesis in a plant starts with light being intercepted by chlorophyll granules. The energy of this light initiates a transport of electrons in the photosynthesis system. This so-called light response causes a measurable variation in fluorescence of the chlorophyll granules. Photosynthesis shows a characteristic trend during the first tens of milliseconds of the start of this process. Stress in plants in particular seems to affect the very first start of photosynthesis. This makes changes in the first milliseconds of photosynthesis a good indicator of the wellbeing of a plant.
The new camera of Wageningen UR Greenhouse Horticulture takes thirty measurements in 0.6 second on the total plant while detecting deviations in the way photosynthesis starts. The new camera works with led light and can also be used under daylight conditions.
The accuracy of the determination by measuring the total plant considerably increases insight in the condition of the plant, says researcher Henk Jalink. He explains: “This is why the camera fits into the ‘speaking plant concept’ because you get immediate information about how the plant is feeling.”
Ready for use in practice
The scientific version of the camera has extensively been tested in the laboratory and on an automated robot arm in a climate cell. One of the reasons for developing this camera was shortening of the measurement time to enable measurement of a large number of plants in a short time. During the development stage the camera has, e.g., been used to test whether lower doses of new formulations of herbicides would be more effective.
But there are many more applications, says Jalink. “You could think of screening plants in a breeding programme for their suitability for cultivation at lower temperatures and lower light intensity or for their resistance against diseases. The camera can also be used in production greenhouses, e.g., for very early detection of Botrytis infestation in roses.” The technique is now being built into a robust camera. This enables use of the camera on location, e.g., by incorporation into a rose sorting machine.