Sustained growth and phosphorus efficiency under iron excess in Paspalum densum, a C4 grass for mining site revegetation

Iron (Fe) is a strong phosphorus (P) chelator in Fe-rich environments. In Fe mining sites, the P deficiency might limit plant development. This study aims to understand how the interaction between the Fe excess and P deficit affects the P-use efficiency and photosynthesis in Paspalum densum, a C4 tropical native grass indicated for use in revegetation of iron mining areas. The plants were exposed to four treatments in Hoagland's nutrient solution: standard (100 % P and 0.019 mM Fe); Fe excess (100 % P and 7 mM Fe); P deficit (1 % P and 0.019 mM Fe); and the combination of P deficit and Fe excess (1 % P and 7 mM Fe). The interaction between Fe excess and P deficiency changed the P allocation in the root and root apoplast. In roots, P deficit caused a higher Fe concentration, and, in the leaf, lower levels of P were found in plants exposed to the Fe excess. The stomatal limitation was the main cause of net photosynthesis decline due to Fe excess in both P doses, however without affecting plant biomass or promoting oxidative damage. The iron excess increased the P-use efficiency (PUE) at the leaf level in P-deficient plants. The photosynthetic PUE and whole biomass PUE were higher due to P deficiency. Therefore, in an environment of Fe toxicity and P deficit, as in areas impacted by Fe mining, the adjustments in P allocation and use efficiency coupled with photosynthetic responses contribute to the P. densum performance during revegetation. '(c) 2023 SAAB. Published by Elsevier B.V. All rights reserved.

Automated summary

This study investigated the interaction between iron excess and phosphorus deficiency in Paspalum densum. The results showed that iron excess decreased phosphorus concentration in roots, while phosphorus deficiency increased iron concentration in leaves. Stomatal limitation was the main cause of decreased photosynthesis due to iron excess. Phosphorus deficiency contributed to higher phosphorus use efficiency and biomass.