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To elucidate the physiological, biochemical and hormonal mechanisms of chilling stress mitigated by drought pretreatment, tomato seedlings (Lycopersicon esculentum cv. C.H Falat) were pretreated by 0, 10 and 20% Polyethylene glycol (PEG) for 7 days followed by subjecting to chilling stress at 3 °C for 6 days and 6 h per day. Results showed that PEG-induced drought improved growth rate of tomato seedling subjected to chilling stress and enhanced their antioxidant enzyme activity, abscisic acid (ABA), anthocyanin accumulation, potassium (K+) and proline content compared with the control (0% PEG) at the end of chilling stress period. PEG pretreatment provided significant protection against chilling stress and reduced poly phenol oxidase (PPO) activity, electrolyte leakage (EL) and H2O2 content in root and leaf of chilled seedlings. Moreover, when PEG pretreatment was applied with chilling stress, we observed an alleviation in the growth impeding and a decrease in chilling symptoms as compared to control seedlings. The highest chilling tolerance was induced by application 20% of PEG. In general, the results indicate that PEG-induced drought, by altering in some tolerant responses, could be effectively used to protect tomato’s seedling from the adverse effects of low temperatures stress.

In this study, the mechanism by which the exogenous application of 150 nM signaling bioactive peptide phytosulfokine α (PSKα) delays senescence and improves antioxidant nutrient accumulation in strawberry fruit during storage at 4 °C for 18 d was investigated. Results showed that the higher endogenous accumulation of PSKα in strawberry fruit treated with 150 nM PSKα may result from the higher expression of PSK3 and PSK6 genes. Besides, the higher endogenous accumulation of Ca2+ in strawberry fruit treated with 150 nM PSKα may be ascribed to the higher cytosolic accumulation of cGMP, resulting from the triggering of endogenous PSKα signaling pathway, represented by higher expression of PSKR1 gene. Besides, the higher endogenous melatonin accumulation resulting from higher expression of TDC, T5H, SNAT, and ASMT genes in strawberry fruit treated with 150 nM PSKα may be ascribed to the higher endogenous accumulation of Ca2+. Moreover, the higher ABTS and DPPH scavenging capacity in strawberry fruit treated with 150 nM PSKα may be ascribed to the higher accumulation of phenols, flavonoids, and anthocyanins, resulting from higher gene expression and activities of PAL and CHS. Based on our findings, the exogenous application of PSKα could be employed as a beneficial procedure for delaying senescence and improving antioxidant nutrient accumulation in strawberry fruit during cold storage, by triggering endogenous PSKα signaling, promoting endogenous melatonin accumulation, and activating the phenylpropanoid pathway.

In this experiment, we tested the exogenous melatonin (0, 1, 10, 100, and 1000 μM) injection at the light green stage for the regulation of strawberry (Fragaria annanaca cv. Sabrina) fruit ripening. Our results showed that a higher endogenous content of melatonin resulting from higher expressions of TDC, SNAT, T5H, and ASMT in response to 1000 μM melatonin injection may be attributed to an accumulation of H2O2 resulting from a higher expression of NADPH oxidase. Also, a higher endogenous accumulation of ABA (due to a higher expression of NCEDs genes) and a higher accumulation of anthocyanin (due to higher expressions of PAL and CHS genes) may be attributed to a higher expression of the GAMYB gene and a lower expression of SnRK2.6 gene, resulting from the endogenous accumulation of melatonin, involved in the ripening of strawberry fruits. Therefore, our results indicate that the exogenous application of melatonin can accelerate the ripening of strawberry fruits by 2–3 days.

In this study, the effects of postharvest salicylic acid, chitosan and salicyloyl chitosan treatments on chilling injury and nutritional quality of pomegranate fruits during storage at 2 °C for 5 months was investigated. Chilling injury symptoms in pomegranate fruits were manifested by external husk browning and internal segment browning. Alleviation impacts of salicyloyl chitosan treatment on pomegranate fruits chilling injury was higher than salicylic acid and chitosan treatments along, which results to delay external and internal browning and increases in electrolyte leakage. Also, pomegranate fruits treated with salicyloyl chitosan exhibited higher membrane unsaturated/saturated fatty acids (unSFA/SFA) ratio. Higher hydrophilic (H-TAA) and lipophilic (L-TAA) antioxidant capacity in pomegranate fruits treated with salicyloyl chitosan results from higher total phenols, anthocyanins and ascorbic acid accumulation. In addition to nutritional quality, pomegranate fruits treated with salicyloyl chitosan exhibited lower weight loss, respiration rate and ethylene production associated with higher firmness, total soluble solids, and titrable acidity as sensory quality. These results suggest that salicyloyl chitosan treatment can be used as promising strategy not only for alleviating chilling injury by maintaining membrane integrity results from higher unSFA/SFA ratio but also for enhancing antioxidant capacity by total phenols, anthocyanins and ascorbic acid accumulation.

The effect of Aloe vera gel (AVG) and basil seed mucilage (BSM) as coating on qualitative attributes of apricot fruits were studied during storage at 2 °C for 28 days. Fruits coating with AVG and BSM alone or in combination with together significantly reduced weight loss, soluble solid content, respiration rate, ethylene production and ripening index in comparison to the uncoated fruits. Also, in coated fruits the firmness and titratable acidity were higher than control fruits. Application of AVG and BSM efficiently increased antioxidant activity, total phenolic content and ascorbic acid of apricot fruits during cold storage. In evaluation sensory attributes, the panelists did not detect any negative effect of AVG and BSM on flavor and external visual aspect of coated fruits. The results demonstrated that addition of BSM to AVG or their individual application as an edible coatings could be a promising approach to maintain postharvest quality and control physiological process of apricot fruits during cold storage.

Pomegranates were treated by dipping with acetyl salicylic acid (ASA) at three concentrations (0.1, 0.5 and 1.0 mM) immediately after harvest and then stored under chilling temperature for 14, 28, 42, 56, 70 and 84 days at 2 °C plus a subsequent period of 4 days at 20 °C. Control fruit exhibited more chilling injury (CI) symptoms (manifested by pitting and browning) than treated fruit during storage, accompanied by increased softening, ion leakage and respiration rate. The ASA treatments were also effective in maintaining higher contents of nutritive (sugars and organic acids) and bioactive compounds (total phenolics and anthocyanins) and total antioxidant activity (TAA), in both hydrophilic (H-TAA) and lipophilic (L-TAA) fractions. These results suggest that ASA could have potential postharvest application for reducing CI, maintain quality and improve the health benefits of pomegranate fruit consumption by increasing the antioxidant capacity.

Pomegranates were treated after harvest with methyl jasmonate (MeJa) or methyl salicylate (MeSa) at two concentrations (0.01 and 0.1 mM), and then stored under chilling temperature for 84 days. Control fruits exhibited chilling injury (CI) symptoms manifested by pitting and browning, the severity being enhanced as storage time advanced, and accompanied by softening and electrolyte leakage (EL). The CI symptoms were significantly reduced by MeJa or MeSa treatments, without significant differences among treatments or applied dose. In addition, both treatments significantly increased total phenolics and anthocyanins with respect to controls. Hydrophilic (H-TAA) and lipophilic (L-TAA) total antioxidant activity decreased in control arils, but in both MeJa and MeSa treated fruits H-TAA increased while no significant changes occurred for L-TAA. Results would suggest that both MeJa and MeSa have potential postharvest applications in reducing CI, maintaining quality and improving the health benefits of pomegranate fruit consumption by increasing the antioxidant capacity.

Pomegranate fruit were treated with salicylic acid (SA) at different concentrations (0.7, 1.4 or 2.0 mM), then stored at 2 °C for 3 months to investigate chilling injury (CI). SA treatments, especially at 2 mM concentration, were highly effective in reducing CI and electrolyte leakage in the husk of pomegranate, as well as ascorbic acid (AA) loss compared with that observed in control fruit.