**6. Results and discussion**

230 Soybean – Genetics and Novel Techniques for Yield Enhancement

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

The hyperspectral reflectance and fluorescence data of the control and treated plants were subjected to statistical analysis through the Student's t-criterion and linear stepwise Discriminant Analysis (DA). Because 1170 reflectance and 910 fluorescence values were available to be used as classification features, it was computationally efficient to select a

The reflectance analysis was performed in four most informative for investigated plants spectral ranges: green (520-580 nm, maximal reflectivity of green vegetation), red (640-680 nm, maximal chlorophyll absorption), red edge (680-720 nm, maximal slope of the reflectance spectra) and the NIR (720-770 nm) (Krezhova et al., 2005, 2007). The statistical significance of the differences between SRC of control and treated plants was examined in eight spectral bands (wavelengths) chosen to be disposed uniformly over the above mentioned ranges (λ1 = 524.29 nm, λ2 = 539.65 nm, λ3 = 552.82 nm, λ4 = 667.33 nm, λ5 = 703.56

The fluorescence spectra were analyzed in five characteristic spectral bands, chosen at wavelengths: 1 (at the middle of the forefront edge), 2 (first maximum), 3 (at the middle between first and second maximum), 4 (second maximum), and 5 (at the middle of the rear slope). They are illustrated in Fig. 11 for a typical fluorescence spectrum of green

The Student's t-criterion and linear DA were applied for determination of the statistically significance of differences at p<0.05 between the means of sets of the values of the reflectance and chlorophyll fluorescence of control and treated plants in the above mentioned wavelengths. They were further regarded as discriminative features. The Student's t-criterion was utilized under the prerequisite for the existence of numerous, independent and approximately of one and the same order factors of small impacts on the variables under examination. DA was used to increase classification accuracy. One output of the method is the determination of the posterior probability that spectral data of a given leaf belongs to the class of control or treated plants. For this purpose discriminant analysis will be implemented in one dimensional spaces defined by the features examined. In some of the cases DA was performed in two or three-dimensional spaces for enhancement of the

**5.2 Chlorophyll fluorescence** 

14th day after the salinity treatment.

subset of bands on the basis of discriminant capability.

nm, λ6 = 719.31 nm, λ7 = 724.31 nm, and λ8 = 758.39 nm).

**5.3 Statistical analysis** 

vegetation.

discriminative possibility.
