Dynamic studies on the transport of micro-heavy metals in plant roots.

采用多室运输箱技术，研究了钙对大麦离体根中锰、锌、镉吸收和运转的影响。将放射性同位素(~(54)Mn&gt；，~(65)Zn&gt；或~(115m)Cd&gt；)标记的测试液供应给切除的根尖，并在无钙或有钙的情况下研究根在根中的分布模式。结果表明：在试验溶液中添加钙降低了离体根对锰的吸收，并显著抑制了锰的转运。随着实验溶液中钙浓度的增加，钙对锰的吸收和转运的抑制作用越来越强，对锌的吸收和转运也有类似的结果。试验溶液中的钙降低了对锌的吸收，并显著抑制了锌的转运；与锰一样，较高浓度的钙对这些作用有严重的影响。在试验溶液中加入钙也明显减少了在所有Cd浓度水平(1，10和100；lt；microg；M)对Cd的吸收。Cd吸收率随试液中钙浓度的增加而降低。然而，钙加速了镉在离体根中的转运，供试液中的镉含量最高可达10&lt；Micro&Gt；M。在100&lt；m~(-1)Cd中，添加Ca对Cd转运的促进作用可忽略不计，添加2，4-二硝基苯酚时，Ca对Cd转运的促进作用显著降低，而添加氯霉素或对氯汞苯磺酸时，Ca对Cd转运的促进作用不明显。当大麦植株在整个生育期内只供应Ca&lt；SO4&gt；，即在此期间的最后一天不供应营养液时，Ca对Cd在离体根中的运转没有促进作用。

The effect of Ca on the absorption and translocation of Mn, Zn and Cd in excised barley roots was studied using a multi-compartment transport box technique. A radioisotope( <^(54)Mn> , <^(65)Zn> or <^(115m)Cd> ) -labelled test solution was supplied to the apexes of excised roots and the distribution pattern in the roots was examined in the absence or presence of Ca. Results obtained were as follows.Addition of Ca to the test solution reduced the absorption of Mn and inhibited drastically its translocation in excised roots. With increasing concentrations of Ca in test solutions, its inhibitory effects on the absorption and translocation of Mn became severe.Similar results were observed for the absorption and translocation of Zn. Ca in the test solution decreased the absorption and inhibited drastically the translocation of Zn; as in the case of Mn, higher concentrations of Ca had severe effects on these functions.It was also evident that the addition of Ca to the test solution reduced the absorption of Cd at all levels of Cd concentration (1, 10, and 100 <micro> M). Cd absorption decreased with increasing concentrations of Ca in the test solution. However, Ca accelerated the translocation of Cd in excised roots supplied with test solutions containing up to 10 <micro> M Cd. At 100 <micro> M Cd, addition of Ca caused a negligibly small acceleration of Cd translocation.The accelerating effect of Ca on Cd translocation, especially "xylem exudation", decreased markedly with the addition of 2,4-dinitrophenol, but not with the addition of chloramphenicol or p-chloromercuribenzene sulphonic acid. When barley plants were supplied with only Ca <SO_4> during the entire growing period, that is, plants were not supplied with nutrient solution on the last day of this period, Ca had no accelerating effect on Cd translocation in excised roots.