Nitrate supply level influences rhizosphere pH value and Fe solubility
Seedlings treated with HN showed an increase of rhizosphere pH under both iron sufficient and deficient conditions, while the rhizosphere pH of the LN treatment was significantly lower than HN treatment (Fig. 2d, e). HN treatment led to higher amount of alkaline in the rhizosphere, which caused reduced solubility of iron in the rhizosphere and more difficulty for seedlings to absorb iron. There was no significant difference of pH when there were no plants in the solutions (Fig. 2c). As shown in Fig. 2, seedling under HN treatment had a higher FCR (Ferric-chelate Reductase) activity under both +Fe and -Fe conditions, while seedling under LN treatment had a lower FCR activity under both +Fe and -Fe conditions (Fig. 2a, b). The above results demonstrated that HN treatment exacerbates iron deficiency symptoms, while LN treatment attenuates plant Fe deficiency symptoms, partially by affecting rhizosphere pH.