In order to investigate the impact of putrescine pre-treatment - which has been proved to be beneficial under normal conditions in Rht wheat lines – the physiological status and some biochemical parameters of dwarf line carrying the alleles Rht-B1c (Rht 3) were tested under osmotic stress compared to the wild, tall genotype (Rht). Gas exchange parameters, level of lipid peroxidation, and the contents of proline and polyamines have been determined with or without putrescine pre-treatment under PEG-induced osmotic stress in the wild and dwarf mutant lines.

No pronounced differences could be detected between the Rht lines in the gas exchange parameters or the proline content under control conditions, while pronounced alteration was observed in the polyamine contents. The Rht 3 dwarf showed lower putrescine and spermidine contents, especially in the roots, but higher leaf spermine level compared to the wild-type.

Despite the fact that the Rht 3 mutant was more tolerant to osmotic stress, PEG treatment induced similar changes in both lines; increased proline and polyamine contents, but the tolerant mutant accumulated higher proline level. Our results confirmed that Rht 3 line is more tolerant to drought stress than the wild type Rht line, which is in relation with the higher accumulation of proline. Although, putrescine pre-treatment modified the PEG-induced osmotic stress responses regarding on proline and polyamine pool, contrary to expectations it has only slight positive effects only in the Rht 3, as lower lipid peroxidation in the roots, and higher proline level was detected in the leaves of the mutant after the combined treatment.

According to our results, responses to excess of polyamines and thus the more activated polyamine metabolism can be more advantageous for dwarf line, and the fine balance in the polymine pool may responsible for a shuttle between the beneficial and deleterious effects of polyamines, which may be responsible for the differences induced in the Rht lines.

Abbreviations – DAP: 1,3-diaminopropane; MDA: malondialdehyde; PA: polyamine; PUT: putrescine; Rht: wild wheat line, Rht 3: mutant wheat line containing the allele for dwarfism, SPD: spermidine; SPM: spermin.

Keywords: dwarf wheat, gas exchange parameters, oxidative stress, polyamines, proline