Cadmium disrupts apoplastic ascorbate redox status in barley root tips

Using a short-term Cd treatment (5–30 min), we analysed the effect of Cd on apoplastic ascorbate redox status and their regeneration during the recovery period in barley root tips. Root growth inhibition induced by 15 µM Cd was detectable after 5 min of exposure and increased in a time-dependent manner up to 15 min of exposure. High 30 µM Cd concentration completely inhibited root growth during the first 6 h after short-term treatment. In parallel with Cd-induced root growth inhibition, a rapid decrease of apoplastic ascorbate dehydroascorbate ratio was observed immediately after short-term treatments. During the recovery from 15 µM Cd short-term treatment, apoplastic ascorbate was rapidly regenerated to the control level in the first root segment containing meristem and elongation zone. In contrast to 15 µM Cd treatment, in 30 µM Cd-treated roots apoplastic ascorbate level was sustained at a significantly lower level compared to control roots. We confirmed that a decrease of apoplastic ascorbate/dehydroascorbate ratio in the elongation zone was associated with root growth inhibition or arrest.

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