Evolutional aspects of photosynthesis formation

Abstract

Aims. The photosynthesis evolution in connection with climate changes and CO₂ content in Earth atmosphere in different geological periods and in last ages is considered. The C₃–type of photosynthesis is more ancient and appeared in period of plant adaptation to life in land and genesis of vascular plants 300 million years ago. The large amount of modern plant species remained the C₃–type of photosynthesis that was effective under low temperatures, humidity and illumination conditions. The C₄–type of photosynthesis was formed under damp and hot climate and decreasing CO₂ content in atmosphere. Methods. The leaves of this type plants have the specific type of structure and high effectiveness of photosynthetic processes under temperatures higher than 25–30 °C. Effectiveness of C₃–type of photosynthesis under high temperature conditions decreases through shift of Rubisco from carboxylation to oxygenation reaction, enhancing photorespiration and CO₂ losses. Results. The development of industrialization led to increasing of CO₂ content in air that increased the rate of photosynthetic gaseous exchange, stimulated increase of plant weight, leaves square, quantity of mesophyll cells and chloroplasts in C₃ and C₄–plants. The relation of carboxylation and oxygenation of Rubisko reaction rates under constant gaze structure of atmosphere and temperature determined by specificity of species but could considerably fluctuate between under changes of relation CO₂ / O₂ and temperature in microspace.

Key words: photosynthesis, evolution, CO₂ content, C₃ and C₄–plants.