ABSTRACT
Pomegranate (Punica granatum) is a non-climacteric fruit with a high antioxidant content in arils and peels, of which 92% are anthocyanins and tannins. However, it is susceptible to chilling injury (CI), a physiological disorder concentrated in the peel, which can affect the organoleptic quality of the fruit. To understand the effects of modified atmosphere and ethylene in responses to stress on the antioxidant quality of the fruit and composition of fatty acids in the peel under CI conditions, the exogenous ethylene treatments (0.5, 1.0, and 1.5 µg L-1), 1-methylcyclopropene (1-MCP; 1 µl L-1), modified atmosphere packaging (MAP: XTend™ bags), combined strategy MAP/1-MCP, and package in macroperforated bags (MPB-control treatment) were evaluated. The assay was performed in cold conditions (2 ± 1°C; 85% RH) to stimulate damage and was sampled for 120 days (+3 days at 20°C). During cold storage, CI symptoms began at 20 days in MPB and at 60 days for all treatments with exogenous ethylene; CI symptoms were delayed up to 120 days in MAP, 1-MCP, and the combined MAP/1-MCP treatment. Damage was concentrated in the peel. Ethylene and MPB-control treatments induced significant electrolyte leakage, lipid peroxidation, and oxidative damage. In contrast, MAP alone or in combination with 1-MCP successfully delayed CI symptoms. However, no significant differences were observed between treatments in fatty acid content, e.g., in the peel, oleic acid, linoleic acid, palmitic acid, but a significant loss was noted after 60 days of storage. Cold storage caused an increase in anthocyanin concentration in the peel and arils, increasing up to 12 times in the peel of the fruit treated with ethylene at the final stage of storage (120 days + 3 days at 20°C), with non-significant differences in the tannin content in the peel. During long-term cold storage of pomegranate, MAP and 1-MCP treatments delay and reduce the appearance of CI symptoms. This long cold storage induces an important decrease in the unsaturated/saturated fatty acid ratio, which is not reversed by any postharvest treatment. A higher unsaturated/saturated fatty acid ratio after 1-MCP treatments showed a protective effect in peel tissues. In addition, it was possible to increase the concentration of anthocyanins in the peel of cold-storage pomegranates treated with ethylene.
ABSTRACT
Carotenoids are essential components of the photosynthetic antenna and reaction center complexes, being also responsible for antioxidant defense, coloration, and many other functions in multiple plant tissues. In tomato, salinity negatively affects the development of vegetative organs and productivity, but according to previous studies it might also increase fruit color and taste, improving its quality, which is a current agricultural challenge. The fruit quality parameters that are increased by salinity are cultivar-specific and include carotenoid, sugar, and organic acid contents. However, the relationship between vegetative and reproductive organs and response to salinity is still poorly understood. Considering this, Solanum lycopersicum cv. Micro-Tom plants were grown in the absence of salt supplementation as well as with increasing concentrations of NaCl for 14 weeks, evaluating plant performance from vegetative to reproductive stages. In response to salinity, plants showed a significant reduction in net photosynthesis, stomatal conductance, PSII quantum yield, and electron transport rate, in addition to an increase in non-photochemical quenching. In line with these responses the number of tomato clusters decreased, and smaller fruits with higher soluble solids content were obtained. Mature-green fruits also displayed a salt-dependent higher induction in the expression of PSY1, PDS, ZDS, and LYCB, key genes of the carotenoid biosynthesis pathway, in correlation with increased lycopene, lutein, ß-carotene, and violaxanthin levels. These results suggest a key relationship between photosynthetic plant response and yield, involving impaired photosynthetic capacity, increased carotenoid-related gene expression, and carotenoid biosynthesis.
ABSTRACT
BACKGROUND: Pomegranate (Punica granatum) is a non-climacteric fruit susceptible to chilling injury (CI) at temperatures below 5 °C. To understand the influences of ethylene and modified atmosphere on CI physiological disorders of pomegranate, exogenous ethrel (0.5, 1 and 1.5 µg L-1 ) treatments, 1-methylcyclopropene (1-MCP) (1 µL L-1 ) exposure, packaging in a modified atmosphere (MAP) (XTend™ bags; StePac, São Paulo, Brazil), a MAP/1-MCP combination, and packaging in macro-perforated bags (MPB) were applied. The treated fruits were cold stored (2 ± 1 °C; 85% relative humidity) and sampled during 120 + 3 days at 20 °C. RESULTS: During cold storage, CI symptoms started at 20 days in MPB and at 60 days for all exogenous ethylene treatments, and were delayed to 120 days in MAP, 1-MCP and MAP/1-MCP treatments. MPB and ethylene treatments induced significant electrolyte leakage, oxidative damage, lipid peroxidation, ethylene and CO2 production, and 1-aminocyclopropane-1-carboxylic acid oxidase activity, without any change in total soluble solids, titratable acidity or skin and aril colours. Conversely, MAP by itself, or in combination with 1-MCP application, effectively delayed CI symptoms. CONCLUSION: During long-term cold storage of this non-climacteric fruit, ethrel application induced endogenous ethylene biosynthesis, accelerating the appearance of CI symptoms in contrast to the observations made for MAP and 1-MCP treatments. © 2018 Society of Chemical Industry.
