THE IMPORTANCE OF THE ROOT-SYSTEM IN ADAPTATION OF SPRING BARLEY GENOTYPES TO THE CONDITIONS OF ENVIRONMENT

Changes in root system growth of spring barley in connection with adaptation of the plant organism to the modified conditions of environment were studied in three-year trials. Short-stem and dwarf genotypes, markedly differentiated in the plant architecture and in their production and adaptation ability, were selected for the study. The spring barley plants were found to respond to the changes in agroecological conditions especially by changing their root growth. The highest variability was determined in root length, then in the number of adventitious roots and volume of the root system. These changes are not variety-specific and are connected with the adaptations to provide the reproduction. The maximum growth of the root system occurs in the stages of shooting to heading, i.e. in the period of elongation growth. The plants react to the soil moisture deficit first by a higher formation of the root biomass. This is reflected in a closer ration of the above-ground dry matter to the roots. Permanent exposure to drought caused growth and metabolic disorders at the end of elongation growth and after heading; these disorders led to a lower above-ground biomass output and to a decrease of grain yield. All the factors acting unfavourably on the root growth for a longer period of time reduce the nutrient uptake from the soil, and slow down the growth of above-ground organs. The highest grain yield was obtained at a high level of mineral nutrients in interaction with the optimum moisture regime. The ratio of above-ground dry matter to the roots was 6:1. A significant narrowing of the dry-matter ratio in this period signals metabolic disorders, later manifesting itself as a lower performance of genotypes. In the agroecosystem the plant provides the offspring with adaption changes in organs in the following sequence: root > tillers > number of kernels per spike > grain weight.