Aims

Plants deploying a phosphorus (P)-mobilising strategy via carboxylate release have relatively high leaf manganese concentrations ([Mn]). Thus, leaf [Mn] is a proxy for the amount of rhizosheath carboxylates. Whether the concentrations of other leaf micronutrient, such as iron ([Fe]), zinc ([Zn]) and copper ([Cu]), show a similar signal for rhizosheath carboxylates is unclear.

Methods

We grew a large number of chickpea genotypes in two glasshouse studies with different growth media, P sources and P levels. Seven weeks after sowing, we determined concentrations of micronutrients in mature leaves, and the quantity and composition of rhizosheath carboxylates.

Results

For 100 genotypes grown in river sand with low P supply, leaf [Fe] (R² = 0.36) and [Zn] (R² = 0.22), like leaf [Mn] (R² = 0.38), were positively correlated with the total amount of rhizosheath carboxylates. For 20 genotypes grown in a soil mixture, leaf [Fe], [Zn], [Cu] and [Mn] showed positive correlations with total rhizosheath carboxylates that were stronger under moderately low P (R² = 0.59, 0.59, 0.54, 0.72) than severely low P (R² = 0.39, 0.28, 0.20, 0.36) or sufficient P (R² = 0.36, 0.00, 0.01, 0.50) supply. Malonate was the predominant carboxylate in the rhizosheath and was significantly correlated with leaf micronutrient concentrations in both experiments.

Conclusions

In addition to leaf [Mn], leaf [Fe] and [Zn] can be used as alternative and easily measurable proxies for belowground carboxylate-releasing processes in chickpea under low-P supply, particularly on moderately low-P soils.

中文翻译：

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除磷含量低外，铁和锌都可为磷供应不足的鹰嘴豆中的根茎类羧酸盐提供代理。

目的

通过羧酸盐释放来部署磷（P）转移策略的植物具有较高的叶锰浓度（[Mn]）。因此，叶[Mn]是根瘤菌羧酸酯含量的代表。尚不清楚其他叶片微量营养元素（例如铁（Fe），锌（Zn）和铜（Cu））的浓度是否显示出根瘤菌羧酸盐的相似信号。

方法

在两项温室研究中，我们用不同的生长培养基，磷源和磷水平培育出大量鹰嘴豆基因型。播种七周后，我们确定了成熟叶片中微量营养素的浓度，以及根瘤菌羧酸盐的数量和组成。

结果

对于低磷供应的河沙中生长的100个基因型，叶片[Fe]（R ²  = 0.36）和[Zn]（R ²  = 0.22），就像叶片[Mn]（R ²  = 0.38）一样，正相关。根茎羧酸盐的总量。对于在土壤混合物中生长的20个基因型，叶片[Fe]，[Zn]，[Cu]和[Mn]与总根茎羧酸盐呈正相关，在较低的中等磷含量下，根茎总羧酸盐更强（R ²  = 0.59、0.59、0.54、0.72 ）严重不足的P（R ²  = 0.39，0.28，0.20，0.36）或足够的P（R ²  = 0.36，0.00，0.01，0.50）供应。丙二酸是根茎中的主要羧酸盐，并且在两个实验中均与叶片微量营养素浓度显着相关。

结论

除叶片[Mn]外，叶片[Fe]和[Zn]还可用作低磷供应下鹰嘴豆地下羧酸盐释放过程的替代且易于测量的代理，特别是在中低磷土壤上。