Copper availability and accumulation by Portulaca oleracea Linn. stem cutting

The Cu accumulation capacity of stem cuttings of Portulaca oleracea was assessed in two different soils, alfisol and vertisol, which differ from each other mainly due to their clay content - several fold lower in the former than in the latter. The DTPA extractable concentration of Cu in soil and the level of its accumulation in stem cuttings were, therefore, greater in alfisol than in vertisol. In the mixed soils, the DTPA extractable as well as plant accumulated levels of Cu decreased with an increase in the proportion of vertisol. With an increase in the soil available and plant accumulated Cu, a decrease has been observed in the ability of stem cuttings to regenerate leaves and roots. As a consequence biomass reduction has been observed with an increase in the concentration of Cu in the soil and plant body. In view of comparatively low availability of Cu in vertisol, regeneration of stem cuttings occurred up to a concentration of 1600 microg of Cu/g of soil, whereas in alfisol it occurred only up to 200 microg of Cu/g of soil. The results of the present study showed that P. oleracea stem cutting is an accumulator of Cu and the availability of Cu in soils could be manipulated through addition of clay since the plant available concentration of Cu is less in the soil (vertisol) with high clay content.