Intercropping is a common agricultural practice improving acquisition of nutrients including iron (Fe). The mechanisms behind this effect, however, are still poorly understood particularly when intercropping cereals with non-legume dicots. To explore the role of root exudates in this positive interaction, oilseed rape (Brassica napus) and barley (Hordeum vulgare) were cultivated in hydroponics either as intercrop (IC) or monocrop (MC) under Fe-sufficient (+Fe) or Fe-deficient (–Fe) conditions. Intercropping improved chlorophyll (Chl) concentration, photosynthesis rates and the “active Fe” concentration in the young leaves of –Fe oilseed rape. Additionally, intercropping under Fe deficiency enhanced the root Fe-reductase activity and the release of organic acids and phenolic compounds by oilseed rape and the release of phytosiderophores by the barley plants. Resupply of sparingly soluble Fe(OH)3 to –Fe plants improved leaf Chl and increased the Fe concentration of barley plants under both MC and IC. Contrastingly, oilseed rape was able to use Fe(OH)₃ only under IC conditions. Moreover, oilseed rape-barley intercropping under + Fe conditions also improved Chl, photosynthesis and nitrogen uptake in oilseed rape. This positive effect of IC independent from Fe acquisition makes intercropping an attractive practice even under non-Fe stress conditions.

间作是改善农业对铁（Fe）等营养素获取的一种普遍做法。然而，这种效果背后的机理仍然知之甚少，特别是在谷物与非豆科双子叶植物间作时。为了探索根分泌物在这种积极的相互作用中的作用，油料油菜（甘蓝型油菜）和大麦（大麦））可以在铁充足（+ Fe）或铁不足（–Fe）的条件下，以间作（IC）或单作（MC）的形式在水培法中栽培。间作提高了–Fe油菜油菜幼叶中的叶绿素（Chl）浓度，光合作用率和“活性Fe”浓度。此外，在铁缺乏下的间作提高了油菜油菜的根系铁还原酶活性，并释放了有机酸和酚类化合物，大麦植物也释放了植物铁载体。在MC和IC下，将少量难溶的Fe（OH）3补给–Fe植株可改善叶片Chl，并提高大麦植株的Fe浓度。相反，油菜可以使用Fe（OH）₃仅在IC条件下。此外，在+ Fe条件下油菜-大麦间作也改善了油菜的Chl，光合作用和氮素吸收。IC的独立于铁吸收的积极作用，即使在非铁胁迫条件下，间作也是一种有吸引力的实践。