Modulation of polyamine balance in Lotus glaber by salinity and arbuscular mycorrhiza

SANNAZZARO A., ECHEVERRÍA M., ALBERTÓ E., RUIZ O., MENÉNDEZ A.

PLANT PHYSIOLOGY AND BIOCHEMISTRY

Elsevier

Año: 2007 vol. 45 p. 39 - 46

0981-9428

In this work we investigated the involvement of Glomus intraradices in the regulation of plant growth, polyamines and proline levels of two Lotus glaber genotypes  differing in salt tolerance, after long-term exposure to saline stress. The experiment consisted of a randomized block design with two factors: (1) mycorrhizal treatments (with or without AM fungus) and (2) two salinity levels of 0 and 200 mM NaCl. Experiments were performed using stem cuttings derived from L. glaber individuals representing a natural population from saline lowlands. One of the most relevant results was the higher content of total free polyamines  in mycorrhized plants compared to non-AM ones in both genotypes. This important difference is particularly relevant under salt stress and may be related to root growth improvements recorded for both genotypes. Colonization by G. intraradices also increased (Spd+Spm)/Put ratio in L. glaber roots. Interestingly, such increment in salt stressed AM plants of the sensitive genotype, was even higher than that produced by salinization or AM symbiosis separately. On the other hand, salinity but not mycorrhizal colonization influenced proline levels in both L. glaber genotypes since high proline accumulation was observed in both genotypes under salt stress conditions. Our results suggest that modulation of polyamine pools can be one of the mechanisms used by AM fungi to improve L. glaber adaptation to saline soils.  Proline accumulation in response to salt stress is a good indicator of stress perception and our results suggest that it could be used as such among L. glaber genotypes differing in salt stress tolerance.