Division 1.7.8 Incubation conditions

Continuous warm or cool white fluorescent lighting should be used to provide a light intensity selected from the range of 85-135 μE·m^–2·s^–1 when measured in a photosynthetically active radiation (400-700 nm) at points the same distance from the light source as the Lemna fronds (equivalent to 6 500-10 000 lux). Any differences from the selected light intensity over the test area should not exceed ± 15 %. The method of light detection and measurement, in particular the type of sensor, will affect the measured value. Spherical sensors (which respond to light from all angles above and below the plane of measurement) and ‘cosine’ sensors (which respond to light from all angles above the plane of measurement) are preferred to unidirectional sensors, and will give higher readings for a multi-point light source of the type described here.

The temperature in the test vessels should be 24 ± 2 °C. The pH of the control medium should not increase by more than 1,5 units during the test. However, deviation of more than 1,5 units would not invalidate the test when it can be shown that validity criteria are met. Additional care is needed on pH drift in special cases such as when testing unstable substances or metals. See (11) for further guidance.