library_construction_protocol: Samples were collected in liquid nitrogen and directly stored at -80 Plants were grown in hydroponics in ambient or elevated CO2 (900 PPM), low (0,5 mM) of high (10 mM) nitrate provision, and iron starvation or not. RNA were extracted using column-based protocols from RNA biology company After the QC procedures, mRNA were enriched using oligo(dT) beads. The mRNA were fragmented randomly by adding fragmentation buffer, then the cDNA were synthesized by using mRNA template and random hexamers primer, after which a custom second-strand synthesis buffer (Illumina), dNTPs, RNase H and DNA polymerase I were added to initiate the second-strand synthesis. After a series of terminal repair, ligation and sequencing adaptor ligation, the double-stranded cDNA library is completed through size selection and PCR enrichment.