Element Recycling Activity during a Life Cycle of a Plant.

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Plant has been integrating the environmental nutritional change into its growth during the life-cycle. Therefore, the element kinetics in a plant is expected to provide a useful information for us to evaluate or protect the environment, from the point of element recycling system. The authors, first of all, had investigated how the elements are partitioned between soil and root, as well as root to the upper part of the plant in caatinger woods, which are the main wood species covering the semi-arid area in Brazil. Then the author analyzed the kinetics of element profile pattern during life-cycle of the plant, morning-glory. In every tissue of the plant, there has been each element gradient formed according to the life cycle and the pattern did not change during juvenile or adult phase of the growth. in the case of morning-glory, most of the transition elements were not transported to the developing seeds. Especially, Mn were accumulated to the old leaf during the growth and was, therefore, returned to the soil as a nutrient to grow the next generation. Most of Al, V and Na were not transported to the upper part of the plant, therefore, in the next generation, there still seems to remain a sufficient amount of these elements. Among the elements investigated, K seemed to be a restricting element to render the next generation grow. Potassium concentration in the leaf stem was always kept higher than that of the leaf, suggesting the regulation of a osmotic pressure of the leaf If additional K was not supplied to the soil, in three generations, K deficient soil might inhibit the plant growth. In the case of caatinger bush, divalent element, such as Ca or Mg tended to be used up in some species. Therefore, in the area investigated, the wood species, which does not uptake divalent element in a large amount should be selectively used to preserve the soil from the decrease of the plant nutrient.