Growth and biomass partitioning in zinc‐toxic bush beans

Abstract

Abstract Bush bean plants (Phaseolus vulgaris L.) were grown during the exponential growth phase in nutrient solution containing 2, 6.6, 9.6 or 13.5 μM Zn. At six different harvest intervals samples were taken for dry weight and Zn content determinations. The primary growth data were fitted to exponential curves, from which the relative growth rates (RGR) and the net assimilation rates (NAR) were derived. With the RGR data the biomass partitioning coefficients of the different organs were calculated. Zinc toxicity generally decreased both the NAR and the growth of all organs, and increased their Zn contents. The relative root expansion rates (RER) and the relative root dry weight growth rates were the most affected parameters, while the leaf expansion rates and the stem dry weight growth rates were hardly affected. The biomass partitioning coefficients indicate that after long‐term exposure to toxic Zn levels the root growth is more affected than the photosynthetate production. This leads to a relative in...