Effect of Ethylene Antagonist Silver Thiosulphate on the Flower Longevity of Clarkia pulchella Pursh.

An experiment was conducted to study the effect of different concentrations of silver thiosulphate (STS) on flower longevity of Clarkia pulchella Pursh. The buds were subjected to 0.1, 0.25, 0.5, 0.75 and 1 mM of STS for 1 h pulse treatment. A separate set of flowers kept in distilled water was designated the control group. STS treatment resulted in improved flower longevity besides maintaining higher fresh and dry mass, water content and floral diameter. Conversely, total phenols, lipid peroxidation and lipoxygenase (LOX) activity decreased. The flowers treated with STS showed a significant increase in the activity of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX). Amongst various grades used, 0.5 mM STS was found to be most effective in enhancing the flower longevity by 1.5 days. The present study reveals that STS maintains lower LOX activity, thereby increased membrane stability index by improving the activity of antioxidant enzymes.

Controlled atmosphere-related injury in ‘Honeycrisp’ apples is associated with γ-aminobutyrate accumulation

Chiu, G. Z., Shelp, B. J., Bowley, S. R., DeEll, J. R. and Bozzo, G. G. 2015. Controlled atmosphere-related injury in ‘Honeycrisp’ apples is associated with γ-aminobutyrate accumulation. Can. J. Plant Sci. 95: 879–886. ‘Honeycrisp’ apples (Malus×domestica Borkh.), including fruit treated with the ethylene antagonist 1-methylcyclopropene (1-MCP), can be susceptible to controlled atmosphere (CA)-related injury of the flesh tissue during storage. To better understand the biomarkers associated with this physiological disorder, we compared the temporal responses of the universal stress signature, γ-aminobutyrate (GABA), and visual symptoms of CA-related injury in apples subjected to elevated CO2. Fruit were treated with or without 1-MCP prior to CA [2.5 kPa O2, 5 (elevated) or 0.03 (ambient) kPa CO2] storage at either 3 or 20°C for up to 24 wk. At 20°C, 1-MCP-treated apples displayed symptoms of CA-related injury by 3 wk of elevated CO2 storage; a similar 15% disorder incidence was apparent by 6 wk in non 1-MCP-treated fruit. A maximal incidence of 30% for this disorder occurred after 24 wk at 3°C in fruit held at elevated CO2, regardless of 1-MCP treatment. At 20°C, GABA levels were 48% higher within 6 wk of the transfer of 1-MCP-treated fruit to elevated CO2. At 3°C, a 2.6-fold increase in GABA level occurred by week 6 of elevated CO2 storage, and was maintained for an additional 18 wk thereafter; a similar change in GABA level was apparent in non 1-MCP-treated fruit, albeit delayed until week 18 of storage. These findings indicate that shifts in GABA are associated with the onset of visual symptoms of CA-related injury in ‘Honeycrisp’ fruit in response to elevated CO2, regardless of 1-MCP.

Cell wall biochemistry of sapodilla (Manilkara zapota) submitted to 1-methylcyclopropene

Sapodilla (Manilkara zapota) is a climacteric fruit that ripens shortly after harvest. Studies on its conservation during storage have been mainly restricted to using low temperatures and modified atmospheres. In this study we investigated the influence of 1-methylcyclopropene (1-MCP) on the physiological and biochemical changes that sapodilla cell wall undergoes during ripening and evaluated its potential to preserve sapodilla fruits at postharvest. Fruits were treated with ethylene antagonist 1-MCP at 300 nL L-1 for 12 h and then stored under a modified atmosphere at 25ºC for 23 d. 1-MCP significantly delayed softening of sapodilla for 11 d as a consequence of inhibition of cell wall degrading enzyme activities, and thus 1-MCP-treated fruit exhibited a less extensive solubilization of polyuronides, hemicellulose and of free neutral sugar when compared to control fruit. Results suggest that delayed softening of sapodilla is largely dependent on ethylene production and perception.

Enzyme activities and pectin breakdown of sapodilla submitted to 1-methylcyclopropene

The objective of this work was to investigate the influence of 1-methylcyclopropene (1-MCP) at 300 nL L-1 on activities of cell wall hidrolytic enzymes and pectin breakdown changes which Sapodilla (Manilkara zapota cv. Itapirema 31) cell wall undergoes during ripening. Sapodilla were treated with ethylene antagonist 1-MCP at 300 nL L-1 for 12 hours and then, stored under a modified atmosphere at 25º C for 23 days. Firmness, total and soluble pectin and cell wall enzymes were monitored during storage. 1-MCP at 300 nL L-1 for 12 hours delayed significantly softening of sapodilla for 11 days at 25º C. 1-MCP postharvest treatment affected the activities of cell wall degrading enzymes pectinmethylesterase and polygalacturonase and completely suppressed increases in beta-galactosidase for 8 days, resulting in less pectin solubilization. Beta-galactosidase seems relevant to softening of sapodilla and is probably responsible for modification of both pectin and xyloglucan-cellulose microfibril network.

Softening and Ripening of ‘Athena’ Cantaloupe (Cucumis melo L. var. reticulatus) Fruit at Three Harvest Maturities in Response to the Ethylene Antagonist 1-methylcyclopropene

Three experiments were performed to characterize the physiological responses of an Eastern United States shipper muskmelon (Cucumis melo L. var. reticulatus ‘Athena’) harvested preripe (¼ slip) and during ripening (half-slip, full-slip) to 1 μL·L−1 1-methylcyclopropene (1-MCP), a potent ethylene antagonist effective at significantly extending the time required for climacteric fruit to complete ripening. In the first experiment, preripe fruit were treated with 1-MCP (18 hour, 20 °C) before storage at 15 °C. Softening of preripe ‘Athena’ was significantly suppressed in response to 1-MCP, with firmness of control and 1-MCP–treated fruit declining ≈50% and ≈36% through 12 and 18 days of storage at 15 °C, respectively. By 21 days of storage, firmness of 1-MCP–treated remained near 70 N, minimally within the upper range of whole-fruit firmness values considered acceptable for consumption (50–75 N). Fruit treated with 1-MCP exhibited significantly lower ethylene production, respiratory rates, and electrolyte leakage throughout storage. In a second experiment, muskmelon were treated with 1-MCP (18 hours, 20 °C) at progressively advanced stages of ripening (half- and full-slip stages). Softening was significantly suppressed in half-slip fruit, declining ≈64% and ≈23% in control and 1-MCP–treated fruit, respectively, during 16 days of storage at 15 °C. Advanced-ripening, full-slip fruit were similarly affected, softening ≈60% and ≈25% in control and 1-MCP–treated fruit, respectively, during 10 days at 15 °C. In a third experiment designed to simulate possible commercial handling protocols, full-slip muskmelon were treated with 1-MCP (24 hours, 10 °C) and held at 10 °C for 5 days before transfer to 20 °C. Mesocarp firmness of 1-MCP and control fruit within 2 days of transfer to 20 °C had decreased ≈40% and ≈54%, respectively, compared with values at the start of the experiment. After an additional 2 days at 20 °C, the mesocarp tissue of the respective treatments had softened 42% and 70%. Fruit treated with the ethylene antagonist showed significantly delayed incidence of surface decay and sunken regions compared with control fruit.