Effect of the Various Concentration of Manganese and Boron in Culture Solutino on the Growth of Soybean

Abstract

Soybean plants were cultured with the Hoagland and Arnon's nutrient solution added manganese and boron in the concentration from 0 to 5.0 p.p.m., and the effect of these ions appeared on the growth of plant were investigated until the time of maturing seeds. And the symptomes caused by the deficiency of manganese and boron sere observed in the relation to the different pH values of solution at the flowering time. The results of experiments ate as follows: (1) Interveinal portions of the leaves turned to yellow color and plants were dwarffed in the deficiency of manganese, so that the dry weight of the plant was only 60%of normal one in the flowering time. As a result of such abnormal growth, the decrease of flower buds and incompletion fruit setting occurred just the same. (2) Excess of manganese concentration, such as 2.5 and 5.0 p.p.m. in the nutrient solution indicated a toxic injury. The grey spots appeared on the lower leaves at first, and the symptom developed progressivelly on the higher parts of plants and color of leaves turned to pale yellow as growth advanced. In consequence, the vegetative growth and the reproductive activity reduced in general. (3) A specific shrink of young leaves and reterdation of root development were seen as first pathological symptom of boron deficiency. In the later stage, the stems died down and branches and flower buds dropped off. Accordingly, the deficiency of boron gave an ill effect to the reproduction than the vegetative growth of soybean compared with it in the case of manganese deficiency: for example, the fruits setting decreased to only 5% of normal plant, but the reduction or the dry weight of plant was, on the contrary, about 10%. (4) 0.5 p.p.m. of boron in the culture solution was sufficient for growth of soybean, and the concentrations of 2.5 and 5.0 p.p.m. acted as a toxin on the growth. The first visible symptom of boron toxcity was a slight thicking of the lower leaves and an upward curling of their edges and soon the edges of leaves turn to pale yellow color. Later, the yellow spots became larger by and by and turn to browen. Both the growth and the yield of soybean were severely effected by toxic action. (5) The total content of iron and manganese in the leaves and stems of the plant grown in the nutrient solution with different pH value decreased inversely to the pH value, but the degree of reduction of iron was smaller than that of manganese at the pH7. (6) The total content of manganese in plant had no relation th the degree of manganese deficiency, but the ratio of total manganese to total iron connected to it. The plant grown at the pH7 of culture solution had the highest values of ratio and indicated the heavily demand of manganese, the next values in the ratio was detected at the pH 4 of culture solution, which appeared fair deficiency symptom of manganese, and the slight manganese deficiency was produced at the pH 8 of culture solution and the plants had lowest values in the ratio. (7) The pH values of the nutrient solution had little effects to the deficiency of boron and its content of plants.