Apogee Instruments S2-431 Посібник користувача - Сторінка 5
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INTRODUCTION
Specific wavelengths of radiation trigger distinct responses in plants. Red and far-red wavelengths are of particular
interest because they influence photosynthetic and morphogenic activity. Phytochrome pigments in plants are
sensitive to varying ratios of red and far-red radiation, providing information to the plant about the light
environment, and therefore, optimal growth patterns. Increasing the fraction of red radiation indicates less
shading and generally results in more conservative vertical growth patterns, while increasing the far-red radiation
fraction indicates more shading and results in more aggressive vertical growth patterns.
Red - far-red sensors are designed to have spectral sensitivities that approximate the phytochrome absorption
spectrum. Red - far-red sensors quantify properties of radiation sources, not plant responses. However, inferences
of plant responses can be made from measurements of the lighting/shading environment, so it is important that
red - far-red sensors have high sensitivity in the wavelength ranges where plants are most sensitive (i.e., the
wavelength ranges that drive the strongest responses in plants), hence red - far-red sensor spectral responses
should approximate the phytochrome absorption spectrum.
The primary application of red - far-red sensors is monitoring plant light environments, including calculation of the
red to far-red ratio (red photon flux density / far-red photon flux density) and far-red fraction (far-red photon flux
density / sum of red and far-red photon flux densities), in photobiology studies (e.g., researching plant
morphogenic activities).
Apogee Instruments S2 series red - far-red radiometers consist of a cast acrylic diffuser, pair of photodiodes that
measure specific wavelength ranges, and signal processing circuitry mounted in an anodized aluminum housing,
and a cable to connect the radiometer to a measurement device. Sensors are potted solid with no internal airspace
and are designed for continuous measurement in indoor and outdoor environments. S2-100 series sensors output
two analog voltages, one for each photodetector, that are directly proportional to red and far-red radiation
incident on a planar surface (does not have to be horizontal), where the radiation emanates from all angles of a
hemisphere.