Putrescine priming effects on chlorophyll fluorescence, antioxidant enzyme activity, and primary metabolite accumulation in maize seedlings under water deficit

This study aimed to evaluate the effect of putrescine priming on the initial growth, chlorophyll fluorescence, primary metabolites accumulation, and antioxidant enzyme activities in two maize hybrids with contrasting drought tolerances. Seeds of Zea mays L. hybrids DKB 390 (drought tolerant) and BRS 1030 (drought sensitive) were primed with putrescine (10 or 100 mu M). Paper rolls moistened with distilled water or mannitol (-0.6 MPa) were maintened at 30 degrees C for 7 d. The growth parameters were higher in the DKB hybrid than in the BRS hybrid. Putrescine priming (10 mu M) promoted the root growth of BRS at levels similar to those of DKB and improved photochemical and non -photochemical quenching and maximum quantum efficiency of BRS seedlings. Higher levels of reducing sugars were found in DKB seedlings when compared to BRS in both roots and leaves, especially with 100 mu M putrescine. Total soluble sugar and starch were lower in the maize roots under water deficit and with 10 mu M putrescine for both hybrids. BRS seedlings showed higher starch content in the leaves in the control and 10 mu M putrescine treatments. Superoxide dismutase was activated in BRS plants by the priming, especially in the roots, but this effect was not observed for catalase, ascorbate, or guaiacol peroxidase, although the DKB seedlings presented much higher guaiacol peroxidade activity than BRS seedlings in both the roots and shoots. In conclusion, putrescine priming (10 M) improved the morphological and biochemical responses of the drought sensitive maize hybrid BRS.