New degreening treatments to improve the quality of citrus fruit combining different periods with and without ethylene exposure

In the Mediterranean area, early-season citrus fruit reach acceptable internal maturity standards for marketing, while the fruit are still green. A degreening treatment is widely used as a postharvest practice to improve the external color. Nevertheless, the application of ethylene during this treatment can be associated with calyx senescence. The aim of this study was to evaluate new degreening treatments in order to reduce this disorder. ‘Clemenules’ mandarins and ‘Navelina’ oranges, harvested at different external colors, were submitted to different degreening treatments, combining periods with and without ethylene exposure. In both cultivars, the periods without ethylene exposure during degreening reduced the incidence of calyx disorders. To obtain a typical ‘Clemenules’ variety color with the lowest incidence of calyx alteration, the optimum degreening treatment was based on 72 h with ethylene and 48 h without ethylene when fruit were harvested with a color index of between −9 and −3. On the other hand, a treatment of 24 h with ethylene plus 48 h without ethylene is recommended for fruit with an external color index higher than −2. For ‘Navelina’ oranges, highly sensitive to calyx senescence during degreening, a treatment consisting of 24 h with ethylene plus 48 h without ethylene is recommended, which involves harvesting the fruit with a color index of over 0.     

外源乙烯对香石竹切花开放的影响

[目的]为了探寻简便安全的方法使香石竹(Dianthus caryophyllus L.)切花在短时间内盛开,以减短存货期并随时满足用花需求。[方法]采用乙烯利溶液喷撒花枝、将乙烯利加入瓶插液以及将乙烯利放在花枝旁边3组处理方法。[结果]适宜的乙烯浓度(环境中乙烯浓度为8.65×10-6 mol/L左右)可促使香石竹切花提前4～5 d盛开,观赏期达7 d,处理的花枝花色正常,最大花径和花枝重有所提高。但是高浓度乙烯、乙烯利溶液喷撒花枝和将乙烯利加入瓶插液均对香石竹产生明显伤害,造成花瓣变色、坏死,花朵不能完全开展。[结论]超过浓度阀值的外源乙烯能使香石竹切花迅速开放,在花枝旁边放置适量乙烯利溶液可有效地促进花朵盛开。     

外源乙烯与脱落酸对牡丹切花衰老进程的影响

通过对胡红牡丹切花施加外源乙烯、脱落酸(ABA)及相应抑制剂,研究了乙烯、ABA与牡丹切花衰老的关系,探讨了乙烯、ABA对切花衰老的调控机理。结果表明,100 mg/L外源乙烯、1 mmol/L ABA均可以明显加速牡丹切花的衰老进程1,mmol/L STS作为乙烯信号转导途径抑制剂可明显延缓切花衰老进程,磷脂酶D(PLD)特异性抑制剂——1-丁醇(1%)可延缓牡丹切花的衰老进程,PLD途径在ABA诱导衰老的信号转导中起重要作用。研究表明,乙烯和ABA信号途径是调控牡丹切花衰老进程中两个重要支路,可共同调控牡丹切花衰老进程,为进一步阐明牡丹花衰老调控机制,克隆牡丹衰老控制基因,培育出长花期牡丹品种奠定了基础;同时为牡丹切花保鲜制剂研究提供了理论依据。     

1-MCP对冬枣冷藏期间乙烯代谢及细胞膜脂过氧化作用的影响

[目的]探讨1-MCP对果实成熟衰老的调控机制,为控制果实成熟衰老进程提供理论依据。[方法]以冬枣为试材,以未经处理的冬枣为对照,测定在冷藏条件下不同浓度1-MCP处理后冬枣的呼吸强度、乙烯释放速率、MDA含量及ACS、ACO、SOD、CAT、POD等酶活性的变化。[结果]经测定,1-MCP在贮藏前期有效抑制了冬枣ACS活性,在贮藏后期有效抑制了冬枣ACO活性,处理果的呼吸强度和乙烯释放速率均低于对照,差异达到显著水平。同时,1-MCP处理有效地减少了MDA的积累,与对照比较,虽然1-MCP处理未改变SOD、CAT和POD的变化趋势,但却显著提高了它们的活性。[结论]1-MCP能有效降低非跃变型果实冬枣的膜脂过氧化水平、呼吸强度和乙烯释放速率,延缓果实衰老进程,并对乙烯的生物合成过程产生抑制。     

Apparent synergism between the positive effects of 1-MCP and modified atmosphere on storage life of banana fruit

Fruit of cv. Gros Michel banana were treated with 1-MCP (1000 nL L⁻¹ for 4 h at 25 °C) and then packed in non-perforated polyethylene (PE) bags for modified atmosphere storage (MAP). The bags were placed in corrugated cardboard boxes and stored at 14 °C. Fruit were removed from cool storage and ripened at room temperature using ethephon. The length of storage life was determined by the change in peel color to yellow, after this ethephon treatment. Fruit treated with 1-MCP + MAP had a storage life of 100 days. The storage life of control fruit (no 1-MCP and no MAP) was 20 days. Fruit held in PE bags without 1-MCP treatment had a 40 day storage life, and the same was found in fruit treated with 1-MCP but without PE bags. 1-MCP is an inhibitor of ethylene action, but also inhibited ethylene production, mainly through inhibition of ACC oxidase activity in the peel. MAP inhibited ethylene production mainly through inhibition of ACC oxidase, both in the peel and pulp. The combination of 1-MCP treatment and MAP storage resulted in much lower ethylene production due to inhibition of both ACC synthase and ACC oxidase activity.     

Rapid ingress of gaseous 1-MCP and acute suppression of ripening following short-term application to midclimacteric tomato under hypobaria

Our previous studies demonstrated that tomato fruit (breaker or pink) exposed at the midclimacteric stage to hypobaric hypoxia for 6 h exhibited transient increased sensitivity to subsaturating levels of 1-methylcyclopene (1-MCP). In the present study, we examined the effect of gaseous 1-MCP (500 nL L⁻¹, 20.8 μmol m⁻³) applied to mid-climacteric (>60% peak ethylene production) tomato fruit under hypobaric hypoxia (10 kPa, 2.1 kPa O₂,) for 1 h. Application of 500 nL L⁻¹ 1-MCP under atmospheric conditions had little effect on softening and timing and magnitude of peak ethylene production, and moderate effects on respiration and lycopene and PG accumulation. By contrast, midclimacteric fruit exposed to 500 nL L⁻¹ gaseous 1-MCP under hypobaric hypoxia for 1 h showed acute disturbance of ripening. Firmness and hue angle declines were delayed for ten days and peak ethylene production for eleven days compared with trends for the other treatments. Maximum ethylene production did not exceed 50% of maxima for the other treatments and a definitive respiratory climacteric was not observed. Accumulation of internal gaseous 1-MCP was enhanced under hypobaric hypoxia. Internal 1-MCP in fruit exposed to 20 μL L⁻¹ 1-MCP (831 μmol m⁻³) under hypobaric hypoxia for 2 or 10 min averaged 7.5 ± 0.5 and 8.7 ± 1.4 μL L⁻¹, respectively, compared with 0.8 ± 0.3 and 3.9 ± 0.7 μL L⁻¹ in fruit exposed under atmospheric conditions. After 1 h exposure, internal 1-MCP averaged 10.8 ± 2.2 μL L⁻¹ under hypobaric hypoxia compared with 5.3 ± 1.4 μL L⁻¹ under atmospheric conditions. The results indicate that high efficacy of 1-MCP applied under hypobaric hypoxia is due to rapid ingress and accumulation of internal gaseous 1-MCP.     

Modeling the effect of preharvest weather conditions on the incidence of soft scald in ‘Honeycrisp’ apples

‘Honeycrisp’ apples show a high susceptibility to physiological disorders such as soft scald. The objective of this study was to identify weather parameters during fruit development that influence soft scald development in ‘Honeycrisp’ apples. Soft scald susceptibility of ‘Honeycrisp’ has been linked to weather conditions during specific periods of the growing season, referenced by given phenological stages. Using weather data and fruit quality analysis data from three sites in Ontario, two sites in Quebec and one site in Nova Scotia for three seasons (2009–2011) and four additional sites in Ontario from 2002–2006, a model for soft scald incidence (SSI) was built to predict the susceptibility of ‘Honeycrisp’ apples prior to storage. This model used primarily two weather variables during three sub-periods of fruit development to accumulate a SSI index (%) during the growing season, from full bloom to harvest time. Relatively wet conditions during phenological stages from full bloom until 10 mm diameter (precipitation > 0.5 mm) and from 10 mm until 50% of final caliber (precipitation > 6.0 mm), cool conditions (temperature < 15 °C) from full bloom until 10 mm diameter, and warm conditions (temperature > 20 °C) from 50 to 80% of final size are conditions that resulted in increased soft scald susceptibility for ‘Honeycrisp’ apples. The SSI model may be used by producers to establish more appropriate marketing and storage strategies depending on levels of susceptibility to soft scald development predicted prior to storage.     

1-MCP对嘎拉苹果呼吸、乙烯产生及贮藏品质的影响

以嘎啦苹果为试材,研究了0℃贮藏期间贮藏30、60、90、120d后转入货架期间1-MCP(1-甲基环丙烯)对果实呼吸速率、乙烯产生速率、硬度、可滴定酸含量及可溶性固形物含量的影响。结果表明,在0℃贮藏条件下,与对照相比,500nL/L浓度的1-MCP可以显著抑制贮藏期间果实呼吸速率和乙烯产生速率,延缓果实硬度和可滴定酸含量的下降,但对可溶性固形物含量无影响;货架期间1-MCP对果实呼吸速率和乙烯产生速率同样有显著的抑制作用,也延缓果实硬度和可滴定酸含量的下降,而对可溶性固形物含量无影响。这些结果表明1-MCP在嘎拉苹果贮藏中具有很好的应用前景。     

不同温度冷藏对油桃生理变化的影响

在(1±0.5)℃、(3±0.5)℃、(5±0.5)℃及常温条件下,研究了油桃的生理变化。结果表明:低温可延缓油桃果肉硬度的下降及叶绿素的分解速度,降低呼吸强度和乙烯释放量,延迟呼吸跃变时期,并抑制了果实后熟过程中PG、CX的活性。其中(1±0.5)℃的效果最为显著,(3±0.5)℃和(5±0.5)℃对果实成熟衰老进程的抑制作用相对较小,且后者还出现冷害现象。