Lux Alexander, Lackovič Andrej, Van Staden Johannes, Lišková Desana, Kohanová Jana, Martinka Michal
Department of Plant Physiology, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina B2, 842 15 Bratislava, Slovak Republic, Institute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava 845 38, Slovak Republic, Research Centre for Plant Growth and Development, School of Biological and Conservation Sciences, University of KwaZulu-Natal Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa and Institute of Botany, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava 845 23, Slovak Republic Department of Plant Physiology, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina B2, 842 15 Bratislava, Slovak Republic, Institute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava 845 38, Slovak Republic, Research Centre for Plant Growth and Development, School of Biological and Conservation Sciences, University of KwaZulu-Natal Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa and Institute of Botany, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava 845 23, Slovak Republic
Department of Plant Physiology, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina B2, 842 15 Bratislava, Slovak Republic, Institute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava 845 38, Slovak Republic, Research Centre for Plant Growth and Development, School of Biological and Conservation Sciences, University of KwaZulu-Natal Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa and Institute of Botany, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava 845 23, Slovak Republic.
Ann Bot. 2015 Jun;115(7):1149-54. doi: 10.1093/aob/mcv051. Epub 2015 May 4.
Contractile roots are known and studied mainly in connection with the process of shrinkage of their basal parts, which acts to pull the shoot of the plant deeper into the ground. Previous studies have shown that the specific structure of these roots results in more intensive water uptake at the base, which is in contrast to regular root types. The purpose of this study was to find out whether the basal parts of contractile roots are also more active in translocation of cadmium to the shoot.
Plants of the South African ornamental species Tritonia gladiolaris were cultivated in vitro for 2 months, at which point they possessed well-developed contractile roots. They were then transferred to Petri dishes with horizontally separated compartments of agar containing 50 µmol Cd(NO3)2 in the region of the root base or the root apex. Seedlings of 4-d-old maize (Zea mays) plants, which do not possess contractile roots, were also transferred to similar Petri dishes. The concentrations of Cd in the leaves of the plants were compared after 10 d of cultivation. Anatomical analyses of Tritonia roots were performed using appropriately stained freehand cross-sections.
The process of contraction required specific anatomical adaptation of the root base in Tritonia, with less lignified and less suberized tissues in comparison with the subapical part of the root. These unusual developmental characteristics were accompanied by more intensive translocation of Cd ions from the basal part of contractile roots to the leaves than from the apical-subapical root parts. The opposite effects were seen in the non-contractile roots of maize, with higher uptake and transport by the apical parts of the root and lower uptake and transport by the basal part.
The specific characteristics of contractile roots may have a significant impact on the uptake of ions, including toxic metals from the soil surface layers. This may be important for plant nutrition, for example in the uptake of nutrients from upper soil layers, which are richer in humus in otherwise nutrient-poor soils, and also has implications for the uptake of surface-soil pollutants.
收缩根主要是在其基部收缩过程的背景下被认识和研究的，该收缩过程能将植物地上部分更深地拉入土中。先前的研究表明，这些根的特殊结构导致基部水分吸收更为强烈，这与常规根类型不同。本研究的目的是探究收缩根的基部在将镉转运到地上部分时是否也更活跃。
南非观赏植物唐菖蒲（Tritonia gladiolaris）的植株在体外培养2个月，此时它们已发育出良好的收缩根。然后将它们转移到培养皿中，培养皿的琼脂水平分隔区在根基部或根尖区域含有50 µmol Cd(NO₃)₂。4日龄不具有收缩根的玉米（Zea mays）植株的幼苗也被转移到类似的培养皿中。培养10天后比较植株叶片中镉的浓度。使用适当染色的徒手横切片对唐菖蒲根进行解剖分析。
收缩过程需要唐菖蒲根基部进行特定的解剖学适应，与根的亚顶端部分相比，其木质化和栓质化组织较少。这些不寻常的发育特征伴随着镉离子从收缩根基部向叶片的转运比从根尖 - 亚顶端根部分更强烈。在玉米的非收缩根中观察到相反的效果，根的顶端部分吸收和运输较高，而基部吸收和运输较低。
收缩根的特殊特征可能对包括从土壤表层吸收有毒金属在内的离子吸收有重大影响。这对于植物营养可能很重要，例如在从上层土壤层吸收养分方面，在上层土壤层腐殖质含量更高而其他方面养分贫瘠的土壤中，这也对表层土壤污染物的吸收有影响。
