Photosynthetic activity of the leaves and productivity of the early-maturing corn hybrid Dorka in the conditions of the northern Non-Chernozem Zone

The paper is devoted to the study of photosynthetic activity and aftereffect of low positive temperature on CO2-gas exchange of the leaves in connection with the productivity of early maturing corn hybrid Dorka in the central agroclimatic region of the Komi Republic (61°40′ N, 50°49′ E). The experiments were conducted in a typical growing season in a plot with a medium-cultivated podzolic soil. The seeds were sown in mid-June by hand in the ridges. By harvesting (I ten-day period of September), the raw weight of the above-ground part of the plants was about 690 g. The main part of the biomass (about 80%) was represented by stems with leaf sheaths, the cobs were absent. The three-year average yield of the green mass amounted to 355 c/ha. It was found that regardless of the age of the plants photosynthetic activity of the leaves increases with increasing illumination. At the intensity of photosynthetically active radiation close to full solar radiation and temperature 20 oC, the net photosynthesis rate of the upper tier leaves of young corn plants was about 14 μmol CO₂/m²s, in mature plants this index did not exceed 8 μmol CO₂/m²s. Keeping young plants (phase of 4–5 leaves) in a cold chamber at 6 ºC for 7 h had little effect on photosynthesis, but reduced leaf respiration. Increasing the exposure to 12 h resulted in the development of the signs of oxidative stress and suppression of assimilation by 40%. The obtained data complete the ecological and biological characterization of the studied corn hybrid. The results of the research show that relatively low assimilatory activity and sensitivity of CO₂ gas exchange to temperature decrease restrain the realization of photosynthetic productivity potential of corn hybrid Dorka in cold climate.

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