No abstract

The study is focused on the evaluation of changes in the hydrological balance of the Krupinica River basin to the Plášťovce station for the entire 90-year period as well as for the three 30-year subperiods 1931-1960, 1961-1990 and 1991-2020. In the first part of the study, the hydrological balance is processed in an annual step on the basis of measured series of average monthly flows from the Krupinica: Plášťovce; monthly precipitation totals on the Krupinica catchment area and average monthly temperatures in the catchment area. The hydrological balance in the monthly step was processed in the second part. Changes in water resources in the river basin over the three mentioned time subperiods were analyzed. The long-term annual precipitation total in the Krupinica River basin for the whole period was 660 mm, the annual runoff depth was 182 mm and the balance evaporation was 478 mm. A comparison of 30-year periods shows a significant decrease in the runoff of Krupinicafrom 231 mm to 144 mm. This was even more pronounced in the runoff coefficient it fell from 0.32 over 0.27 to 0.21 in the last period 1991-2020. In the third part, a simple regression relationship between runoff, precipitation and air temperature was derived to estimate the future development of the annual runoff from the basin. The relationship shows that a 100 mm decrease in precipitation in the Krupinica River basin will cause an average decrease of 52 mm in runoff. And an increase in the average annual temperature by 1°C in the Krupinica River basin results in a decrease in runoff of about 33.5 mm.

Reassessing the hydrological characteristics with regard to drought is very important in the context of a changing climate. In this paper, we evaluate the drought in terms of changes in hydrological characteristics for the 20-year period 2001-2020. The evaluation of changes is based on a comparison of data for this period with the currently valid reference period 1961-2000 in 13 selected water-gauging stations. In the analysis of the occurrence of subnormal mean annual discharges (Qr <90% Qa,1961-2000, in most of the evaluated stations, the percentage incidence of such years is higher in the period 2001-2020 than in the reference period. The distribution of runoff throughout the year in the period 2001-2020 in comparison with the reference period in most stations confirms the changes identified in the previous evaluation of the period 2001-2015, i.e. the transfer of part of the usual increased spring runoff to previous, winter months. An exception was water-gauging stations on streams in the mountainous areas of northern Slovakia, where changes are reflected to a lesser extent.

The effects of different spectral region of excitation and detection of chlorophyll (Chl) a fluorescence at room temperature on the estimation of excitation energy utilization within photosystem (PS) 2 were studied in wild-type barley (Hordeum vulgare L. cv. Bonus) and its Chl b-less mutant chlorina f2 grown under low and high irradiances [100 and 1 000 µmol(photon) m -2 s -1 ]. Three measuring spectral regimes were applied using a PAM 101 fluorometer: (1) excitation in the red region (maximum at the wavelength of 649 nm) and detection in the far-red region beyond 710 nm, (2) excitation in the blue region (maximum at the wavelength of 461 nm) and detection beyond 710 nm, and (3) excitation in the blue region and detection in the red region (660-710 nm). Non-photochemical quenching of maximal (NPQ) and minimal fluorescence (SV 0 ), determined by detecting Chl a fluorescence beyond 710 nm, were significantly higher for blue excitation as compared to red excitation. We suggest that this results from higher non-radiative dissipation of absorbed excitation energy within light-harvesting complexes of PS2 (LHC2) due to preferential excitation of LHC2 by blue radiation and from the lower contribution of PS1 emission to the detected fluorescence in the case of blue excitation. Detection of Chl a fluorescence originating preferentially from PS2 (i.e. in the range of 660-710 nm) led to pronounced increase of NPQ, SV 0 , and the PS2 photochemical efficiencies (F V /F M and F V '/F M '), indicating considerable underestimation of these parameters using the standard set-up of PAM 101. Hence PS1 contribution to the minimal fluorescence level in the irradiance-adapted state may reach up to about 80 %.Additional key words: Hordeum; non-photochemical quenching; non-radiative dissipation; PAM fluorometer; photosystems 1 and 2.

The present study was conducted to examine changes in photosynthetic pigment composition and functional state of the thylakoid membranes during the individual steps of preparation of samples that are intended for a separation of pigmentprotein complexes by nondenaturing polyacrylamide gel electrophoresis. The thylakoid membranes were isolated from barley leaves (Hordeum vulgare L.) grown under low irradiance (50 µmol m -2 s -1 ). Functional state of the thylakoid membrane preparations was evaluated by determination of the maximal photochemical efficiency of photosystem (PS) II (F V /F M ) and by analysis of excitation and emission spectra of chlorophyll a (Chl a) fluorescence at 77 K. All measurements were done at three phases of preparation of the samples: (1) in the suspensions of osmotically-shocked broken chloroplasts, (2) thylakoid membranes in extraction buffer containing Tris, glycine, and glycerol and (3) thylakoid membranes solubilized with a detergent decyl-β-D-maltosid. F V /F M was reduced from 0.815 in the first step to 0.723 in the second step and to values close to zero in solubilized membranes. Pigment composition was not pronouncedly changed during preparation of the thylakoid membrane samples. Isolation of thylakoid membranes affected the efficiency of excitation energy transfer within PSII complexes only slightly. Emission and excitation fluorescence spectra of the solubilized membranes resemble spectra of trimers of PSII light-harvesting complexes (LHCII). Despite a disrupted excitation energy transfer from LHCII to PSII antenna core in solubilized membranes, energy transfer from Chl b and carotenoids to emission forms of Chl a within LHCII trimers remained effective.Additional key words: 77-K chlorophyll fluorescence spectra; Hordeum vulgare; photochemical efficiency; polyacrylamide gel electrophoresis; thylakoid membranes isolation.