The PAR / temperature leafclip is available to facilitate measurements made under ambient light conditions using the FMS 2 chlorophyll fluorometer. Chlorophyll fluorescence measurements can be made quite satisfactorily without the leafclip but a value of PAR from the light sensor on the leafclip is essential for the estimation of electron transport rate by the FMS software. Other chlorophyll fluorescence parameters are unaffected if the system is operated without the leafclip.

The FMS/PTL leafclip consists of a sprung upper section which gently grips the sample in a gentle clamping action.

A grooved neck mounted at 60° to the plane of the sample accommodates the fibre optic cable which is slid into position. Marked graduations on the neck can be aligned with graduations on the fibre optic cable termination to reference its position for future work, a retaining screw locks it into position throughout the experiment. The rest of the fibre optic cable may be looped over the leafclip and hooked to the rear of the clip to help support its weight. A fully cosine corrected PAR sensor and 0 - 90°C thermocouple are also fitted to the FMS/PTL.

An electrical connection to the Leafclip socket on the front panel of the FMS 2 chlorophyll fluorometer enables use of the remote trigger switch to activate / abort measurements in Local mode and connect the leafclip thermocouple and light sensor to the control unit. The leafclip may be held in the hand if multiple samples are being studied or mounted on a standard tripod mount via a thread in the lower clip section for fixed-position work.

The PAR sensor has been designed for both recording of ambient light intensities during fluorescence analysis and measurement of FMS actinic and saturating light sources during instrument setup.

A leafclip system has been developed for situations where ambient light is to be excluded from the sample during measurement. This is suitable for experiments requiring dark-adapted measurements e.g. screening applications measuring Fv/Fm or situations which require adaptation of tissue to standardised doses of actinic light.

The system consists of small, lightweight leafclips and 2 different types of fibre optic cable adapter. The leafclip itself has a small shutter plate which should be closed over the leaf when the clip is attached so that light is excluded and dark adaptation takes place.

The body of the clips are constructed from white plastic to minimise the effects of heat build-up on the leaf during the period when the clip is in place.

The locating ring section of the clip which interfaces with the fibre optic adapter is also constructed from white plastic.

The sample rests on a foam pad whilst in the clip in order to minimise damage to the structure of the sample. The shutter plate should be closed to exclude light from the sample during dark adaptation.

During dark adaptation, all the reaction centres are fully oxidised and available for photochemistry and any chlorophyll fluorescence yield is quenched. This process takes a variable amount of time and depends upon plant species, light history prior to the dark transition and whether or not the plant is stressed. Typically, 15 - 20 minutes may be required to dark adapt effectively. In order to reduce waiting time before measurement, a number of leaves may be dark adapted simultaneously using several leafclips.

The fibre optic cable is inserted into either one of the adapters which in turn, fits over the locating ring of the leafclip. The closed fibre optic adapter is suitable for applications where ambient light must be excluded whilst the open adapter is suitable for studies under ambient conditions.