Onuchak, Natalia. V. (Tetiiv Institute of Agroecology and Biotechnology, 15, Stepovoy Street, Kashperivka, Tetiiv area, Kyiv Region, 09812, Ukraine; Phone: +380 4460 26370;

Fax: +380 4460 26370; Email: onuchak@ukr.net)

Reaction of Plant Cenosis on Global Change of СО₂ Concentration in the Earth Atmosphere

Nataliia Vasylivna Onuchak *

The purpose of the present research is to appraise tensity and change dynamics of the cenotic interactions in cenosis of the cereals depending on genotype and level of nitric nutrition under СО₂ enrichment of the atmosphere during the period of plant vegetation. Experiments have been conducted on the cenosis model in four-chamber hermetic phytothrone. The concentration of СО₂ was maintained at a natural level of (350 mcl/l) for 24 hours, which is to be a control in two cameras, whereas in the other two cameras СО₂ concentration was doubled (700 mcl/l), which is to be experimental. Plants have been grown under optimal conditions of cultivation: power of radiant flow – 300 Wt/m² PAR, temperature – 20⁰C at day-time and 17⁰C at night-time, photoperiod – 16 hours, air humidity – 60 ± 7%. The experiment has been conducted in the soil culture. Various combinations of mineral salts have been composed in this way in order to create variants of nitric nutrition containing 100, 150, 200, 400 и 600 mg N on 100 g of soil. 2-3 consecutive long experiments were conducted in each studied sort of cereals including all the plant vegetation. Ontogenetic change appraisal of cenosis condition has allowed to distinguish period of most intensive interactions in cenosis – cenotic interactions point. System aspiration to the stability is most expressed in that point which defines maximum amplitude of changes and allows to use them as description of cenosis condition in the time of study of increased СО₂ concentration (700 mcl/l) influence on plant cenosis structure depending on genotypes of which they are made.

In the present research the role of spring cereals genotype (wheat, barley) on the low background of nitric nutrition under СО₂ enrichment of the atmosphere has been examined. The specifics in forming of agrocenosis structure by cereals have been studied. The researches have shown that rise of СО₂ level leads to intensification of plant growth processes. It has been ascertained that under atmospheric СО₂ enrichment it is observed coming of the cenotic interactions point in lower biomass of the cenosis in studied genotypes of both barley and wheat than under normal СО₂ concentration. At the same time cenotic interactions point comes in an earlier period of growth. It has also been ascertained that under high СО₂ level competitive relations in plant cenosis are arising earlier however in majority of genotypes they are going less hard. Conclusion has been made regarding clear compensatory mechanism of individual growth in cereal cenosis depending on СО₂ concentration, level of illumination and genotype competitiveness. In the present research it has also been studied the role of nitric nutrition of cereals. The research shows that under high atmosphere СО₂ concentration the efficacy of light use by unit of assimilative surface of the plant leaf under condition of sufficient level of nitrogen in the soil is raised. Plant competitiveness is being reduced and the plants are becoming more tolerant to the conditions of illumination level. Results have shown that rise of nitric nutrition is a necessary condition to yield crop increase under rise of СО₂ level in atmosphere as it is necessary sufficient amount of nitrogen in the soil for effective use of СО₂ level. As a result of the conducted researches it has been revealed that level optimization of nitric nutrition in the soil allows to lay a base for effective use of СО₂ in the atmosphere, particularly in case of doubling СО₂ concentration and also to increase grain productivity of cultivated cereals.