**5.2 Chlorophyll fluorescence**

The spectral measurements of the chlorophyll fluorescence were carried out under laboratory conditions using the same portable fibre-optics spectrometer (USB2000). Data were collected in the VIS and NIR spectral ranges (600-900) nm in 910 spectral bands with a step of 0.3 nm where the main part of the emitted from the plants fluorescence radiation is concentrated. As a source of actinic light, a LED diode with light output maximum at 470 nm and light intensity 507 mol m-2 s-1 was used. The tested leaves were dark adapted before the measurements for ten minutes. The abaxial side of the leaves was irradiated with actinic light and the exited fluorescence was measured from the adbaxial leaf surface. The control of the spectrometer and the acquisition and processing of data were carried out by means of specialized software. The measurements were conducted on fresh detached leaves from by 20 plants of the each group of plants in the 4th trifoliate expanded leave node on the 14th day after the salinity treatment.
