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The work is focused on monitoring changes in benthic communities in the longitudinal gradient of the river Lužnice. The river flows through to the pond area Třeboňsko and the largest pond of the Czech Republic - Rožmberk. It is examine affect of pond on benthic communities. The work involves collecting benthos according to the PERLA method on four profile in four seasons, the analysis of chemical parameters and data processing. The values of SI (saprobiological index) in the longitudinal gradient were from SI 1.8 to SI 2.6. SI values were at the outflow of Rožmberk higher than at inflow. The lowest values were in the first profile Suchdol (SI 1,8 ? SI 2,1) and higher values were in the last profile Vlkov (SI 2,4 ? 2,6). The chemical parameters at outflow were observed increased values of BOD5, TOC, NL105, NL505, chlorophyll and total P but lower values of nitrogen forms (Ntotal,NH4, N-NO3-). On the each profile was the significant change in the incidence or absence of certain groups. Profiles Suchdol and Hlína were diferent than Lužnice and Vlkov especially in the presence of stoneflies, dragonflies, beetles, and individuals generally indicates good water quality. Profiles at outflows from Rožmberk (Lužnice and Vlkov) showed a continued presence of bloodsuckers and more species indicating high organic pollution. NMDS method confirmed impact of sites in communities rather than period (R2 = 0.6 at significance level of p = 0.001).

I created 12 populations crossing four varieties of spring barley Jersey, Diplom, Saloon, Prestige. Varieties with greater root system size (RSS) better use soil water and nutrients in dry environment than varieties with smaller RSS. I studied effect of selection in 12 populations developed by mutual crossing of 4 parents in F3 generation as response on selection in preceding generation F2 for great (A) and small (B) . Six plants with the greatest (A) and six with the smallest (B) RSS from 24 plants were selected in each population. In F2 generation had the A-plants RSS greater by 39.7% and B plants smaller by 43.1% in comparison with the average of the four parents. In progeny (F3 generation) the difference amounted +3.9% and -2.3% for RSS and +8.1% and -5.1% for grain yield respectively. The selection differences in F2 generation were inherited into F3 by 9.8% in A- and by 5.3% in B-selection. Varieties Saloon and Diplom increased and other two varieties decreased the RSS in their progenies. Combinations Diplom x Saloon and Diplom x Prestige showed the greatest RSS (6.48 and 6.22 nF, respectively), the smallest RSS had a combination with only 1.81 nF. It can be concluded that recombination of some varieties showed greater RSS in progenies than was that of the parents, inheritance was comparable with grain yield and selection for the trait was effective. Selection differences were reflected about two times more in grain yield.

This bachelor work is dealing with the composition of natural food of fish in the chosen streams. Many samples were taken from five streams during the spring and autumn seasons at the same area called the Šumava Mountains according to PERLA method. The first two streams are called Hamerský and Pestřice. They are the inlets of Lipno reservoir. The next three - Horský, Mlýnský and Bukový belong to the River Danube. Despite of the fact that these streams are situated at the same area and have very similar flows, fish abundancy and the way of farming in their basins differ. These aspects influenced the benthos composition in every single stream and that is why this work should provide survey about the composition and biomass of benthos in particular watercourse. The richest is Mlýnský stream in term of the abundance of benthic organism. By the streams which are parts of basins of Danube river, was the most dominant kind Gammarus Fossarum and Limnius perrisi. By the Lipno reservoir inflows, there were the most numerous may flies (Ephemeroptera), represented mostly by the tribe Baetis (Hamerský stream) and the Trichoptera kind with the dominant Anomallopterygella chauviniana from the Trichoptera group (Pestřice stream). There are some differences of the composition and abundance of benthic groups between streams belonging to basins of Danube river and the streams influent to Lipno reservoir. According to the particularity of index number, Lipno?s streams are similar with the streams influent to Danube river from 23% (Pestřice stream) and from 45% (Hamerský stream).