Pulse-amplitude modulated (PAM) chlorophyll fluorometry in combination with saturating pulse analysis of fluorescence quenching is now a standard technique to assess plant photosynthesis.
In the 1990s, the Walz Teaching-PAM fluorometer (PAM-200) carried PAM fluorometry into university classrooms. Since then, there has been considerable progress in LED and PC technology, enabling the development of a powerful and versatile, and at the same time compact teaching fluorometer: the JUNIOR-PAM.
The JUNIOR-PAM features the smallest size and best price-performance ratio of all PAM fluorometers. It excels by its simplicity and ease of operation.
The JUNIOR-PAM is controlled by PC via USB interface: the fluorometer does not require a separate power supply as it is powered by the PC via the USB line.
The same WinControl-3 software is provided as for research PAM fluorometers like the MONITORING-PAM. In addition, WinControl-3 can be operated in a simplified mode to assist teaching in elementary courses.
The JUNIOR-PAM is particularly well suited for teaching classes and workshops, where availability of a larger number of instruments is essential for gaining hands-on experience.
The JUNIOR-PAM fluorometer is a miniaturized instrument capable to carry out the full range of saturation pulse analysis of photosystem II. A small box of 11.5 x 6.5 x 3.0 cm contains all optical and electronic components. The fluorometer is connected to the sample via a 50 cm long single plastic fiber with 1.5 mm diameter.
The JUNIOR-PAM employs the same blue (460 nm) power LED for pulse modulated fluorescence excitation, actinic illumination and saturating pulses. Also, the fluorometer features a far-red LED for selective excitation of PS I and determination of the Fo’ level fluorescence.
JUNIOR-PAM with 60° leaf-clip mounted on swivel-type support
Two different types of leaf-clips are provided, a 60° clip for measurements in ambient light and a magnetic leaf clip for Fo-Fm and Fv/Fm measurements.
An optional monitoring leaf-clip is available to measure ambient light intensity (PAR, μmol m-2 s-1) at leaf level and leaf temperature (see Accessories).
The two versions of the JUNIOR-PAM fluorometer provide visible light of different spectral composition: the BLUE version emits between 400 and 500 nm with a maximum around 445 nm. The WHITE version shows a narrow-band blue emission peaking around 445 nm plus a broad band emission ranging from 475 to 650 nm (Fig. 1).
Both versions are equipped with a far red LED with maximal emission around 745 and an emission range from 675 to 800 nm.
Figure 1: Typical emission spectra of LEDs normalized to their maximum. Blue line, blue LED of JUNIOR-PAM. Grey line, white LED of JUNIOR-PAM/W. Dark red line, far red LED of JUNIOR-PAM or JUNIOR-PAM/W. Max, peak wavelength in nm. FWHM, full width at half maximum in nm.
Also the spectral window for fluorescence detection distinguishes the two versions. The BLUE version detects fluorescence at wavelengths > 630 nm and the WHITE version at wavelengths > 650 nm (Fig. 2).
The BLUE version is the standard type of the JUNIOR-PAM and suitable for fluorescence measurements with most eukaryotic algae and higher plants. For algae absorbing poorly in the blue, as can be the case in species of the phylum cyanobacteria, the WHITE version yield significantly better fluorescence signals than the BLUE version.
Figure 2: Transmittance spectra of red filters positioned in front of the fluorescence detector. Red curve, JUNIOR-PAM. Dark red curve, JUNIOR-PAM/W.