Rhizodeposition of Zea mays L. as affected by heterosis

The objective of the present work was to investigate in a field experiment the quantity and quality of rhizodeposits of different parental inbred lines (Lo1016 and Lo964, B73 and H99) and hybrids of Zea mays L. Rhizosphere soil was collected after 40 days and several properties were determined: pH, organic carbon, total nitrogen, acid and alkaline phosphatases, organic acids, bioavailable phosphorous, a-amino nitrogen, total phenols, total root-derived rhizodeposits. The results showed that heterosis induced more qualitative differences within the genotypes as d13C, TOC and TN did not show any significant differences. The two groups of genotypes enhance phosphorous availability adopting two different strategies. In the first group, B736H99 shows the best phenological performance as well as the highest concentration of bioavailable P, result which is correlated with a high organic acid concentration (in particular succinic and acetic acid), total phenols, a-amino nitrogen and acid phosphatase activity. There is thus a strict relationship between the phenological superiority of this particular hybrid and its ability to modify the chemistry of its rhizosphere whereas the second hybrid (Lo10166Lo964) seems to have developed different strategies as for example changing the root morphology, stimulating microbial biomass or favouring mycorrhizal symbiosis.