Comparison of chromium tolerance in several plant species based on growth analysis

Abstract

Tolerance of various plants to Cr was studied at the following different Cr6+ concentrations of water cultural solutions: 0.0, 0.5, 2.0, 8.0 mg l^-1 (w/v). The plants used for the trials were Oryza sativa L., Phaseolus vulgaris L., Morus bombycis Koidz, Brassica oleracea var. captata L., Glycine max (L.) Merr., Brassica campestris L.var. pervirdis. The cultivation was designed for 10 days of operation to measure the dry weight growth (dry increment) of the plants and the concentration change of Cr in plant tissues. Growth analysis has been used to analyze the tolerance of plant toward Cr. The plants were categorized into three types based on their Cr tolerance through the measurement of dry weight growth (dry increment), relative growth rate (RGR), net assimilation rate (NAR) and leaf dry weight ratios (LWR) of the plants before, during and after the cultivation. High tolerance plants were Oryza sativa L. and Phaseolus vulgaris L.; medium tolerance plants were Morus bombycis Koidz. and Brassica oleracea var. captata L.; and the low or poor tolerance plants were Glycine max (L.) Merr. And Brassica campestris L.var. pervirdis.
Increase of Cr concentration added to various plants was linear to the dry weight growth, relative growth rate and net assimilation rate. The Cr concentration of the upper parts of plants above the soil and the Cr transferring rate to those parts dominated the Cr tolerance of a plant. This because the increase of the Cr concentration of the upper parts of plants above the soil and the Cr transferring rate to those parts can inhibit or interfere the physiological functioning a plant, which results in the decrease of organic assimilation capacity or photosynthesis function of the plant, measuring as the decreases of chlorophyll contents, dry weight growth, relative growth rate and net assimilation rate.