Ears Plant Photosynthesis Monitoring B.V. (EARS-P2M)

EARS is a high-tech remote sensing company specialized in remote and near sensing techniques.

Our Mission

EARS-P2M is carrying out our near sensing activities. These focus on the use of plant chlorophyll fluorescence signal for photosynthesis monitoring. Since 1983 we have carried out extensive research in the field of laser induced fluorescence. In the 1990's we have developed and patented our own Plant Photosynthesis Meter (EARS-PPM). This handheld instrument is a modulated saturation pulse fluorometer.

Our Vision

Applications have been and are developed in the field of greenhouse climate control, irrigation management and reduction of herbicide use in agriculture. Other measuring techniques, like high resolution spectrometry, and other applications, like optimizing plant and algae growth, have our continuous attention.

Application Range

The miniPPM has a wide range of applications in research, education and practice. It is also very suitable for education purposes, and a unique gadget to anyone who wants to know more about the health and growth of plants.The miniPPM has a wide range of applications in research, education and practice. It is also very suitable for education purposes, and a unique gadget to anyone who wants to know more about the health and growth of plants.

About Mini PPM

The new miniPPM is the third generation of our plant photosynthesis meter. It features the latest innovations in optics and electronics and is based on a new, advanced measuring concept. Electronics innovation and smaller components made it possible to design an entirely new device, much smaller and lighter in weight than previous versions, without compromising on quality and accuracy. Yet the instrument is simple in operation: just press the button and a photosynthesis measurement is completed within a second. Laboratory tests show excellent properties. Measurements are stable and reproducible.

All miniPPM devices have warranty for one year

Shipping info
All miniPPM models are shipped from the Netherlands , shipping price will be calculated according to the location of purchase.

Differences between miniPPM models

There are several miniPPM versions. The table below shows the differences in functionality and use.

100 150 200 300
Fluorescence in ambient light (F)
Maximum fluorescence (Fm)
Photosynthesis yield (Y)
Photosynthetic Active Radiation (PAR)
Measurements at all light levels
Photosynthesis rate in ambient light (P)
Long unattended measuring series
Photosynthesis at pre-defined light levels
Light - Photosynthesis curves
User interface
LCD display with various read-out options
Read out and storage on microSD card
On board control and storage
PC control (USB) and storage
Herbicide efficacy / damage
Quality of plants, vegetables, fruit
Seedling screening for breeding
Plant photosynthesis yield monitoring
Plant photosynthesis rate monitoring
Steering of light climate in greenhouses
Irrigation management
Additional deliverables
Protective case
USB Data Cable
USB Charger
4 adapter set for different countries mains
2 GB MicroSD Card
microSD to USB adapter
English / Dutch Manual
1 Year Warranty
Optional items
12V fast charger / power suppply
RS-232 communication port
RS-485 communication port
433 or 915* MHz wireless remote PC connection
Tripod stand with gooseneck and 1/4" UNC adapter

Herbicide efficacy

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Genetically modified plants

Quite some research has been done on the genetic modification of plants. An important part is dedicated to the development of herbicide-resistant crop species. In many cases photosynthesis inhibitors are concerned. These act by chemical binding to essential protein complexes of the photo-systems. By genetic modification of these proteins, it is possible to create plants that are resistant to specific herbicides. Nature has already incorporated very efficient proteins in the photosystems of plants, giving maximum photosynthesis of about 80%. Therefore such genetic modifications usually have a negative effect on the photosynthetic and consequently growth capacity of the plant.

In the field also genetic modifications occur. Under the influence of intensive herbicide treatment, resistant weed mutants may develop. An example is Solanum nigrum (Black night shade). The resistant version is not sensitive to atrazine. Measurements with the PPM have shown that the photosynthesis efficiency of this mutant is notably lower. So far research concentrated on the increase of herbicide resistance in plants, but not much attention has been paid to the effects of the genetic modification on productivity. The PPM may be used to investigate this.

Preventing light damage

Many plants are stressed and may be damaged by too much light. During day-time, two phases of photosynthesis are discerned. At the low light level the photosynthesis rate is limited by the available light. With increasing light level the photosynthesis rate reaches the point where the energy for the reaction and the uptake of CO2 are in equilibrium. At higher light levels the photosynthesis cannot increase anymore and the excess light will inhibit photosynthesis and may damage the plant ("burning").

Greenhouse plant growers will use light screens to reduce the light level. However, they do not know the exact light level to start screening the plants. Moreover, the screening light level is somewhat variable and will not only depend on species but also on variety, light adaptation after winter, possible water shortage and CO2 levels applied in the greenhouse. Growers can use the PPM to measure exactly the screening light level of their plants.

The miniPPM-300 is most suitable for this purpose. This instrument measures fully automatically the photosynthesis light curve of a plant species. The figure above shows an example of such a measurement. The red line presents the photosynthesis rate as a function of the photosynthetic active radiation intensity (PAR). Optimum photosynthesis occurs at 780 micromole/m2s. Photosynthesis at that level is about 190 micromole/m2s, which corresponds to a dry matter production of 1.9 gram/m2hr. At higher light levels photosynthesis decreases again and damage may occur due to increasing heat development. Since PAR light levels in greenhouses on sunny days can easily reach 1700 µmole/m2s screening is essential to prevent damage to the plant. As a rule of the fist, screening is necessary if the photosynthesis yield measured with the PPM decreases below 40%.

NL Office

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