Effect of high solar radiation on polyamines levels on apple exocarp

LAURA VITA; SANTIAGO MAIALE; VALENTIN TASSILE; GRACIELA COLAVITA

Barcelona

Congreso; XXII Reunión de la Sociedad Española de Fisiología Vegetal; 2017

High solar radiation stress causes an excessive production of reactive oxygen species that can not be counteracted by the antioxidant mechanisms in apple exocarp. This imbalance alters exocarp oxidative metabolism, maturity indices and pigments. Within the antioxidant plants defense under adverse environmental conditions, polyamines (PAs), such as Putrescine (Put), Spermidine (Spd) and Spermine (Spm) have been reported. However, there is limited information about PAs content in apple exocarp exposed to high solar radiation. At fruit maturity state, lipid peroxidation (thiobarbituric acid-reactive substances, TBARs), antioxidant activity (DPPH radical-scavenging) and free PAs content were analyzed in high solar radiation exposed exocarp (E) and non-exposed exocarp (NE) of Granny Smith apples. High solar radiation stress produced an increase in lipid peroxidation in E (59.8 nmol.g-1FW) compared to NE (43.8 nmol.g-1FW). Antioxidant capacity also increased 31,6% in E. Put was the polyamine found in highest proportion followed by Spd and Spm. PAs content increased significantly 39.7% in E in regard to NE. Put concentration was 159.0 nmol.g-1FW in NE, while in E was 201.4 nmol.g-1FW. Spd and Spm increased 63.6% and 40.8% respectively in E compared to NE. Chlorophyll content decreased from 62.5 µg.g-1FW in NE to 28.5 µg.g-1FW in E. Since Spd and Spm have been reported as direct free radical scavenger, it is possible that the improvement of the antioxidant capacity in apple exposed exocarp is related to Spd and Spm increase. However, this higher antioxidant capacity and particularly PAs level were not adecuate to avoid higher lipid peroxidation, chlorophyll degradation and high solar radiation symptoms expression.