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2 Acta Physiologiae Plantarum

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Cadmium disrupts apoplastic ascorbate redox status in barley root tips

100%

Bocova B. , Mistrik I. , Pavlovkin J. , Tamas L.

nr 6

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.

Primary stress response induced by different elements is mediated through auxin signalling in barley root tip

75%

Zelinova V. , Alemayehu A. , Bocova B. , Huttova J. , Mistrik I. , Tamas L.

nr 11

Short-term exposure (15 min) of barley roots to different chemical elements revealed that Cd, Cu, Hg and Pb were the most toxic ones causing a marked root growth inhibition even at µM concentrations. Gd, La, Al, Cr, As, Zn, Ni and Se inhibited root growth to a similar extent only at mM concentrations. Despite the high 20 mM concentration, Co caused only a slight, while Mn, Mg or Ca did not evoke any root growth inhibition. Elements at concentrations inhibiting root growth caused a considerable accumulation of indole-3-acetic acid in the root apex. While Cr, As and Zn inhibited, Cd, Cu, Hg, Pb, Gd, La and Al markedly stimulated the generation of reactive oxygen species in the beginning of differentiation zone. Auxin signalling inhibitor alleviated or prevented root growth inhibition, reactive oxygen species generation and the stimulation of lipoxygenase and glutathione peroxidase activity by various elements, indicating a key role of auxin signalling in the stress response of barley root tip. On the other hand, it did not affect or even had an additive effect on dehydroascorbate reductase and ascorbic acid oxidase activity in combination with different elements. Our results indicate that the primary response of barley roots to the presence of various chemical elements during the shortterm treatment is not a specific but rather a general adaptive stress response enabling the plant to survive adverse conditions.