The Effect of Seed Vernalization and Irradiation on Growth and Photosynthesis of Field Bean Plants (Vicia faba L. minor) and on Nitrogenase Activity of Root Nodules

The effect of seed vernalization (2–3°C; 36 days) and irradiation intensity during vegetation of field bean upon growth and maximum leaf photosynthesis (P_max) as well as specific (SNA) and total nitrogenase activity (TNA) of root nodules was investigated. The measurements were performed at the initial stage of pod development of varieties with undetermined (cv. Nadwiśański) and determined (cv. Tibo) growth habit. In comparison with plants in shading, those which grew in full irradiation produced larger leaf area and more dry weight, achieving higher P_max values. Stimulation of leaf area enlargement and dry weight increase, especially in respect to the dry weight of underground parts had a positive and significant effect upon TNA value. Accumulation of dry weight was higher in vernalized than non-vernalized plants, but only in the case of cv. Nadwiślański, in full irradiation conditions. In the case of plants grown in poorer irradiation conditions TNA values were about 68 % (cv. Nadwiślański) and 54 % (cv. Tibo) lower, due to significant limitation of root nodules. TNA value of vernalized cv. Nadwiślański plants was 66 % higher in comparison with non-vernalized plants. However, the effect was visible only in full irradiation conditions, due to simultaneous greater intensity of root nodules production and higher SNA value. A positive effect of vernalization could also be observed in the decrease of a negative correlation between dry weight of root nodules and SNA in both varieties.