Mbah Glory Chinonye, Dakora Felix Dapare
1Department of Crop Sciences, Tshwane University of Technology, Pretoria, 0001 South Africa.
2Department of Chemistry, Arcadia Campus, Tshwane University of Technology, Private Bag X680, 175 Nelson Mandela Drive, Pretoria, 0001 South Africa.
Symbiosis. 2018;75(3):205-216. doi: 10.1007/s13199-017-0531-2. Epub 2017 Dec 15.
Although nitrate is known to inhibit nodulation and N fixation in symbiotic legumes, little is known about its effect on the uptake and accumulation of trace elements such as Fe, Zn, Mn and Cu. The aim of this study was to evaluate the effect of 5 mM NO supply, either with or without rhizobial inoculation, on nodulation, nodule functioning and micronutrient levels in the shoots of soybean ( L.Merr.), Bambara groundnut ( L. Vedc) and Kersting's groundnut ( Harm). The results showed reduction in plant growth, nodule formation and nodule dry matter by the supply of 5 mM NO to inoculated seedlings of all three species. Nitrate inhibition respectively caused 1.2, 1.4, and 1.5-fold decrease in nodule number per plant in Bambara groundnut, soybean and Kersting's bean, which resulted in 2.3, 3.3 and 4.5-fold reduction in nodule dry weight of the test species (in that order). The application of 5 mM NO to soybean plants also resulted in 2.5, 4.0 and 5.4-fold decrease in shoot accumulation of Fe, Zn and Mn, respectively, when compared to the purely symbiotic control plants. Furthermore, we observed 1.3, 1.8 and 1.3-fold decreases in the concentration of Zn, Mn and Cu in shoots of inoculated Bambara groundnut with NO supply, levels lower than those found in soybean. With Kersting's groundnut, shoot concentration of Fe, Zn and Cu were higher with the application of 5 mM NO to inoculated plants when compared to the purely symbiotic treatment, which was opposite to soybean. But pure NOfeeding of this species respectively resulted in 2.0, 1.4 and 1.3-fold decreases in Fe, Zn and Cu relative to inoculated NO-fed plants. Clearly, NO supply to landraces/genotypes of the three legume species did not only inhibit nodule formation and functioning, it also reduced shoot micronutrient levels in soybean and Bambara groundnut, but not Kersting's bean.
尽管已知硝酸盐会抑制共生豆科植物的结瘤和固氮作用，但对于其对铁、锌、锰和铜等微量元素吸收和积累的影响却知之甚少。本研究的目的是评估5 mM硝酸盐供应（有无根瘤菌接种）对大豆（Glycine max (L.) Merr.）、 Bambara花生（Vigna subterranea (L.) Verdc.）和Kersting花生（Macrotyloma geocarpum (Harms)）地上部结瘤、根瘤功能和微量营养素水平的影响。结果表明，向所有三个物种的接种幼苗供应5 mM硝酸盐会导致植物生长、结瘤和根瘤干物质减少。硝酸盐抑制分别导致Bambara花生、大豆和Kersting花生单株根瘤数减少1.2、1.4和1.5倍，导致受试物种根瘤干重分别减少2.3、3.3和4.5倍（按此顺序）。与纯共生对照植物相比，向大豆植株施用5 mM硝酸盐还分别导致地上部铁、锌和锰积累量减少2.5、4.0和5.4倍。此外，我们观察到供应硝酸盐的接种Bambara花生地上部锌、锰和铜浓度分别降低了1.3、1.8和1.3倍，其水平低于大豆中的水平。对于Kersting花生，与纯共生处理相比，向接种植物施用5 mM硝酸盐时地上部铁、锌和铜浓度更高，这与大豆相反。但该物种单纯供应硝酸盐相对于接种硝酸盐处理的植物分别导致铁、锌和铜减少2.0、1.4和1.3倍。显然，向这三种豆科植物的地方品种/基因型供应硝酸盐不仅抑制结瘤和根瘤功能，还降低了大豆和Bambara花生地上部的微量营养素水平，但对Kersting花生没有影响。
