The aim of this study is to investigate the effects of oxalic acid on the uptake, accumulation and oxidative stress of Cr 3+ ion by sorrel (Hibiscus sabdariffa L.) seedlings in hydroponic solution. The growth of 8 weeks old seedlings exposed to 0, 5, 10, 20 and 40 mg/L Cr 3+ ion and 20.0 mM oxalic acid was monitored in a greenhouse under controlled conditions. The application of oxalic acid for 10 days prior to harvest revealed that Cr 3+ ion accumulated significantly in the roots (p < 0.05)

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... h only a little translocated to the shoots. Hibiscus sabdariffa L. accumulated high Cr 3+ ion concentration (344.44 mg/kg) in the root at a concentration of 40 mg/L.The application of oxalic acid had inhibitory effects on the root and shoot biomass compared with that in the control. Therefore, chelation enhanced Cr 3+ ion uptake by Hibiscus sabdariffa L. The Cr 3+ ion-induced proline accumulation in shoots was also determined. There is no much difference in proline content of both the chelated and un-chelated treatment, however, the proline content decreased slightly with increasing Cr 3+ ion in the nutrients solution. Free proline is known to accumulate in plants under heavy metals exposure and is considered to be involved in stress resistance.