Changes of proline concentration and electrolyte leakage in the selected species of the Panicoideae tribe under water deficit.

The theme of this thesis is the impact of water deficit on the concentration of proline and electrolyte leakage from representatives of the Panicoideae tribe. The impact of drought on agricultural production in the environment of the Czech Republic is currently an important issue. The exceptionall dry year of 2014/2015 and the associated water deficit in the soil had an impact mainly on the harvest of wide-row crops, including maize. Representatives of the Panicoideae tribe - sorghum and foxtail millet are the most drought-resistance crops in the world. Sorghum and foxtail millet belong to II. group of cereals like maize. Sorghum and foxtail millet show lower transpiration coefficient than maize, they also tolerates less demanding growing conditions and are more resistant to diseases and pests. They also compete with maize in a wide range of applications. It is therefore appropriate to determine how these crops respond to water deficit during their ontogenetic development. For the purposes of this experiment genotypes originating from conditions of temperate climate were selected, this genotypes have a shorter growing season. A short growing season is an important factor in the timing of the harvest of the late sown crops in our climate. The aim of the thesis was to determine and evaluate the impact of water deficit on the concentration of proline and electrolyte leakage in selected genotypes of sorghum and foxtail millet and on the basis of the results to select genotypes with high resistance to water deficit. Based on the aims the following hypotheses were set: to determine whether there are differences in the concentration of proline and electrolyte leakage between selected genotypes depending on the effect of water deficit and whether there are differences in these physiological characteristics in response to water deficit between sorghum and foxtail millet. To fulfill the objectives and evaluation the hypothesis was based on the greenhouse experiment with selected genotypes of sorghum and foxtail millet at the Department of Botany and Plant Physiology in the Czech University of Life Sciences Prague. The experiment included 4 genotypes of the species Sorghum bicolor (L.) Moench. (Sorghum): 1216, 30485, Barnard Red and Ruzrok and one variety of the species Setaria italica (L.) Beauv. (Foxtail millet) Ruberit. A total of 4 variants were designated for the experiment (one control and three under the influence of water deficit in different times). The plants in the control variant were full irrigated throughout the experiment. Variant KS was irrigated for the first 14 days, followed by 10 days without watering and the last 4 days were again irrigated. Plants in variant SK were under the influence of water deficit for the first 10 days of the experiment, then 18 days with watering and the plants in the variant SS were without watering for the first 10 days, for the next 4 days were without watering, then the same pattern was repeated: 10 days without and 4 days with watering. Physiological characteristics were observed in plants in the developmental stages BBCH 14-16. The concentration of proline was determined by measuring the absorbance of the samples formed by the reaction with ninhydrin. Subsequently, the measured values were compared with the calibration curve. To measure the sample absorbance at 520 nm a spectrophotometer Hellios gama (Thermo) was used. Electrolyte leakage on discs made from leafs was measured with electrical conductivity meter GRYF 158 (HB Griffin, Ltd.). The obtained results show that the proline concentration increased in response to water stress, since the highest concentration of proline was detected in plants growing in the most stressed variant of SS (670.13 micrograms) compared with other variants of stress. Plants variant KS (643.85 micrograms) showed a higher accumulation than the proline in variant SK (636.69 micrograms). The highest concentration of proline was measured on a genotype in the variety of sorghum Ruzrok (642.94 micrograms). The lowest content of proline was found in the variety of sorghum 1216 (623.78 micrograms), this value was also the only significant difference from the contents of proline to other genotypes. Which at least partly confirms the proposed hypothesis that there are differences in the content of proline between genotypes. The highest electrolyte leakage cell damage was respectively exhibited in plants from the variant SS (39.56%). Plants of the SK variant showed a higher rate of cell damage (32.95%) than plants from the variant KS (29.88%). The lowest cell damage was exhibited in plants grown under control conditions, which again indicates that damage cells increases in response to water deficit. In this experiment the highest degree of cell damage was found in the variety of sorghum 1216 (29.26%) and lowest cell damage was observed in the variety of sorghum Ruzrok (27.03%). A significant different degree of cell damage appeared only in the variety foxtail millet Ruberit (28.6%), which confirms our hypothesis that there are differences in the electrolyte leakage between sorghum and foxtail millet. The hypotheses were not fully confirmed by the experiment. Nevertheless, on the basis of obtained results we conclude that the least drought-resistance genotype is the 1216 variety and the best adapted to the water deficit was the Ruzrok variety. It also confirmed that the higher proline accumulation may protect the plant against the negative effects of water deficit on the cell membranes, which is then reflected in a reduced electrolyte leakage