Ammonia may be an indicator of senescence and may also indicate stressful conditions

Ammonia accumulation in plant tissues is a consequence of protein catabolism and is reported to increase during senescence in various leafy and floral vegetables. Here we studied postharvest ammonia production to understand its relationship to the onset of senescence and to injury induced by modified atmospheres. The effect of storage temperature (0, 5 or 10?C) on ammonia accumulation and quality changes was studied in 5 cultivars of rocket leaves. The Weibull model was used to fit ammonia changes of each cultivar and storage temperature with a R2 value higher than 0.98. A 2 way ANOVA on the kinetic constant obtained with fixed n factors, showed that temperature was the only significant factor affecting ammonia accumulation with time, and fitting data averaged across cultivars resulted in an even higher R2 of 0.99. Arrhenius model allowed to establish an Energy of activation of 198 kJ when cultivar values were averaged. Moreover a highly significant correlation was found with color changes (Hue angle), indicating that ammonia accumulation may be directly or indirectly related to phenomena associated with senescence. The effect of CO2 and O2 concentrations was studied on mint leaves, where increasing CO2 levels induced very evident browning; there were concurrent increases in ammonia with increasing CO2 concentrations and time of storage at 5?C and 99% RH. A higher ammonia accumulation was also observed with fresh-cut artichokes that browned during storage in atmospheres with CO2 concentrations higher than 12%. In cauliflower florets high CO2 concentrations (15%) with 1 or 5% oxygen resulted in increased ammonia accumulation and product discoloration, whereas moderate CO2 levels (7.5%) at 5?C helped preserve product quality. Under these conditions, intermediate ammonia levels were found, as compared to the low accumulation in samples stored in air and in low oxygen, but which resulted in lower quality with time. These results demonstrate that ammonia may be an indicator of senescence and may also indicate stressful conditions, such as damaging CO2 atmospheres. ? SourcesAmmonia accumulation in plant tissues: a potentially useful indicator of physiological stressM. Luisa Amodio1, Giancarlo Colelli1, Marita Cantwell21 Department of Science of Agriculture, Food and Environment, University of Foggia, Via Napoli 25, 71122 Foggia, Italy2 Shields Ave, Davis CA 95616, United States of AmericaVIII International Postharvest Symposium; Cartagena, Spain, 21-24 June 2016 Foto taken of?Biblioteca Digital