Aims

This study aimed at revealing the mechanisms of zinc(Zn)-induced root growth inhibition in the Zn hyperaccumulator Noccaea caerulescens and the excluder Microthlaspi perfoliatum to shed light on the intriguing question whether there is any selectivity in the Zn effects on root cell division and elongation.

Methods

Zinc effects on various parameters characterizing root cell division and elongation were studied. Total Zn uptake, accumulation, root-to-shoot translocation, and distribution over the root tip tissues as well as metal-induced oxidative stress were also assessed.

Results

Similar degrees of root growth inhibition were achieved when the Zn concentration in the medium and Zn content in the roots were 150 and 5 times higher, respectively, in the hyperaccumulator, compared to the excluder. Zinc accumulated in the cell walls and protoplasts in the root meristem and elongation zone. Although Zn negatively affected both root cell division and elongation, at a similar degree of root growth inhibition, the contribution of the inhibition of cell division was greater in N. caerulescens compared to M. perfoliatum, as the decrease in the meristem length, the number of meristematic cells in a file, and the mitotic index were more prominent in the hyperaccumulator.

Conclusions

Greater contribution of the inhibition of cell division in N. caerulescens compared to M. perfoliatum at a similar degree of root growth inhibition seemed to be partly determined by a stronger degree of oxidative stress and disturbance of mineral nutrition in the roots of the hyperaccumulator, owing to a much higher Zn accumulation.

中文翻译：

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锌诱导的锌超积累植物 Noccaea caerulescens 和非积累植物 Microthlaspi perfoliatum 根系生长抑制机制

 目标

本研究旨在揭示锌（Zn）诱导的锌超积累植物Noccaea caerulescens和排除者Microthlaspi perfoliatum中锌（Zn）诱导的根生长抑制机制，以阐明锌对根细胞分裂和伸长的影响是否具有选择性这一有趣的问题。 。

 方法

研究了锌对表征根细胞分裂和伸长的各种参数的影响。还评估了总锌的吸收、积累、根到茎的易位、根尖组织的分布以及金属诱导的氧化应激。

 结果

与排除器相比，当超积累器中的培养基中的锌浓度和根中的锌含量分别高150倍和5倍时，可以实现相似程度的根生长抑制。锌积累在根分生组织和伸长区的细胞壁和原生质体中。虽然 Zn 对根细胞分裂和伸长都有负面影响，但在相似程度的根生长抑制下，与M. perfoliatum相比， N. caerulescens细胞分裂的抑制作用更大，因为分生组织长度、数量减少。分生组织细胞呈文件状排列，有丝分裂指数在超富集植物中更为突出。

 结论

与M. perfoliatum相比，在相似的根生长抑制程度下， N. caerulescens对细胞分裂的抑制作用更大，这似乎部分是由超积累植物根部更强的氧化应激和矿物质营养干扰决定的，因为达到更高的锌积累。