Characteristics of the photosynthetic activity of corn using different drugs under stress

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Goal. To study under controlled conditions the effect of hormonal preparations based on humus extracts and anti-stress stimulants with a high content of amino acids and biologically active substances on the development of corn under conditions of stress, as well as their effect on the photosynthetic activity of plants.
 Methods. The research was carried out in a climatic chamber (a room with adjustable control of temperature, daylight and air humidity) of the Ukrainian research plant quarantine station of the Institute of Plant Protection of the National Academy of Sciences. Photosynthetic activity was measured using a portable fluorometer «Floratest». During the growing season, two foliar feedings were carried out in the phase of development of corn VVSN 12, the first application of drugs during the growing season — VVSN 13, — the second application of drugs during the vegetation period — VVSN 14.
 Results. The analysis of the induction curves of chlorophyll fluorescence and the indicators of the maximum background fluorescence showed a difference between the plants that were under soil moisture of 70% and 50% RH. When corn plants were in a state close to stress for a long time, the difference between the curves of chlorophyll fluorescence intensity between the two controls increased. The use of the studied drugs provided the finding of the indicator of the maximum value of fluorescence induction above the dry control in all variants of the experiment. Best results provided: preparation B (high concentrated suspension for nutrition and plant stress decreasing based upon the humus extract. They contented N — 150 g/l, K2O — 300 g/l, Mg — 30 g/l, metal cations in В, Cu, Fe, Mn and Zn with additional adhesive effects and surfactant), at rate of application 0.5 and 0.25 l/ha; Axofol (high concentrated suspension from extract of brown algae Ascophyllum nodosum with microelements, B — 38.1 g/l, Mn — 10.2 g/l, Zn — 6.4 g/l) at rate of application 1.0 and 0.5 l/ha.
 Conclusions. As the time of corn plants being in a state close to stress increases, the difference between the curve of chlorophyll fluorescence intensity in the wet control and the dry control increases. The use of the studied drugs provided the finding of the indicator of the maximum value of fluorescence induction above the dry control in all variants of the experiment. The use of the researched preparations in conditions of soil moisture of 50% ensured the improvement of vegetation indicators of plants.