Mineralization and herbage recovery of animal manure nitrogen after application to various soil types

Aims

The study aims (1) to evaluate the effect of Mesorhizobium tianshanense on plant proline and polyamine levels of Lotus tenuis and its modulatory effect during plant response to short-term salt stress and (2) to compare these effects with those caused by mycorrhizal symbiosis.

Methods

Experiments consisted of a randomized factorial design of two factors: salinity (two levels, 0 and 150 mM NaCl) and symbiosis (three levels, uninoculated, Glomus intraradices, and M. tianshanense).

Results

Salinization led to increased proline levels regardless of plant organ and symbiotic status, excepting mycorrhizal L. tenuis roots. Salinity diminished the total polyamine level of control and rhizobial plants but not in mycorrhizal ones. Variations in the pattern response of the three individual polyamines (putrescine, spermidine, and spermine) differed in accordance with the symbiotic status of the plant, highlighting a divergence on proline and polyamine metabolisms between rhizobial and mycorrhizal symbiosis.

Conclusions

Spermidine and spermine contributed the most with the salt-induced root polyamine increment observed upon salinization in roots of nodulated plants, suggesting that these polyamines might mediate an adaptive role of the plant–M. tianshanense symbiosis in L. tenuis plants growing in a saline environment.