Photochemical activity of chloroplasts of isogenic lines (E genes) of soybean (Glycine max (L.) Merr.) under different periods of red-light irradiation

The effect of different periods of red-light (RL, 660 nm) irradiation of plants on the biomass, leaf area, chlorophyll content, level of the Hill reaction and photophosphorylation in short-day (SD) and photoperiodical neutral (PhPN) lines of soybean have been studied in vegetation experiments. The objects of study were the isogenic lines (E genes) of soybean (Glycine max (L.) Merr.), Clark variety. The SD (E1E2E3) and PhPN lines (e1e2e3) were used. The plants were grown in a vegetation chamber in the soil culture (black soil). Plants of SD and PhPN lines were grown in 9 vessels of three liters volume. 10–12 plants were grown in each vessel. The constant growing conditions were provided during the experiment: temperature – 20–24/17–20°С (day/night), soil moisture – 60–70 % of the total soil moisture content, intensity of illumination – 20 klx, photoperiod duration – 10 hours. After 4–5 weeks of vegetation (after the second true leaf formation), plants of each line in three vessels were irradiated for 30 minutes with low intensity red light at the beginning (experiment 1) or in the middle of the dark period (experiment 2). The light diodes emitting in the region of 630±10 nm were used for plant irradiation. Other plants in three vessels of each line, which were not illuminated by the red light, were used as a control group. It was shown that under the short day the SD line in the control group passed to flowering 43±1.8 days after germination and PhPN line – 44±2.2 days after germination. The red-light irradiation, both before the beginning and in the middle of night, caused a delay of the transition to flowering in the SD line by 5±1 and 7±2.2 days, respectively. In the PhPN line, changing flowering period due to RL was not established. In the SD line, activation of the phytochromes by RL before the dark period caused an increase of the biomass, leaf area, total chlorophyll content, reduction of potassium ferrocyanide and photophosphorylation by isolated chloroplasts per chlorophyll of one leaf. While interruption of the night by RL caused decrease of these parameters and Hill reaction intensity per 1 mg of chlorophyll. The effect of RL on the studied parameters in the PhPN soybean line has not been detected.