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Ultraviolet-B (UV–B) radiation as an environmental potential elicitor induces the synthesis of plant secondary metabolites. The effects of UV-B radiation on photosynthetic pigments and dry weight, biochemical and molecular features of old and young leaves of Salvia verticillata were investigated. Plants were exposed to 10.97 kJ m−2 day−1 of biologically effective UV-B radiation for up to 10 days. The sampling process was performed in four steps: 1, 5, 10, and 13 days (recovery time) after the start of irradiation. As a result of plant investment in primary and secondary metabolism, the production of phenolic compounds increased, while chlorophyll levels and leaf dry weight (%) declined. Under long-term UV-B exposure, young leaves exhibited the most significant reduction in chlorophyll a and b content and leaf dry weight. The highest level of total phenol (1.34-fold) and flavonoid concentration (2-fold) relative to the control was observed on the 5th day and recovery time, respectively. Young leaves demonstrated the highest amount of phenolic acids in recovery time. Young leaves on the 5th day of the experiment exerted the highest level of antioxidant activity when compared to the control. A positive correlation was observed between antioxidant activity and the amount of phenolic compounds. Regarding the expression of phenylpropanoid pathway genes, UV-B enhanced the expression of phenylalanine ammonia-lyase, tyrosine aminotransferase, and rosmarinic acid synthase with the highest level in young leaves on the 10th day. Overall, young leaves of S. verticillata indicated higher sensitivity to UV-B radiation and developed more tangible reactions to such radiation.

In this study, we tested the exogenous application of phytosulfokine α (PSKα) for delaying the yellowing of broccoli florets during cold storage. Our results showed that the lower yellowing in broccoli florets treated with 150 nM PSKα was probably due to the higher endogenous accumulation of PSKα, leading to the endogenous accumulation of guanosine 3′, 5′-cyclic monophosphate (cGMP). Besides, broccoli florets treated with 150 nM PSKα exhibited a higher accumulation of phenols and flavonoids by triggering gene expression and activities of phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS). Moreover, the higher expression of L‐galactotno‐1,4‐lactone dehydrogenase (GLDH) gene and the lower expression of ascorbic acid oxidase (AAO) gene in broccoli florets treated with 150 nM PSKα may be the reasons for the higher accumulation of ascorbic acid. In conclusion, the exogenous application of PSKα is a promising strategy in delaying the yellowing and preserving the nutritional quality of broccoli florets during cold storage.

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 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.

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.

Methyl salicylate (MeSA) is a signal molecule in plant responses to biotic and abiotic stress and elicits plant resistance against chilling injury. An experiment was conducted to determine whether MeSA applied at 0, 0.25, 0.5, and 0.75 mM as a seed soak or foliar application would protect cucumber (Cucumis sativus L.) seedlings subjected to chilling at 3°C for 5 days. The MeSA improved growth rate of cucumber seedlings and increased relative leaf chlorophyll and relative water contents by inhibiting malondialdehyde and H2O2 accumulation and increasing proline and antioxidant capacity. MeSA was most effective when applied using the seed soak method at 0.5 and 0.75 mM.

Chilling temperatures lead to numerous physiological disturbances in the cells of chilling-sensitive plants and result in chilling injury and death of tropical and subtropical plants such as watermelon. In this study, the possibility of cold stress tolerance enhancing of watermelon seedling (Citrullus lanatus) by exogenous application of Salicylic acid (SA) was investigated. SA was applied through seed soaking or foliar spray at 0, 0.5, 1 and 1.5 mM concentration. After SA treatment, the seedlings were subjected to chilling 5 h/day at 4°C for 5 days. Statistical analysis showed significant effects of the application methods and SA concentrations on plant growth parameters, photosynthetic pigments, electrolyte leakage, proline and chilling injury index. SA application improved growth parameters and increased chlorophyll content of watermelon seedling subjected to chilling stress and provided significant protection against chilling stress compared to non-SA-treated seedlings. Although two SA application methods improved chilling stress tolerance, seed soaking method provided better protection compared to foliar spray method. SA ameliorated the injury caused by chilling stress via inhibiting proline accumulation and leaf electrolyte leakage. The highest cold tolerance was obtained with 0.5 mM SA application. Results indicate that SA could be used effectively to protect watermelon seedling from damaging effects of chilling stress at the early stages of growth.

The effect of pre-storage application of calcium chloride (CaCl 2 ) on chilling resistance and calcium (Ca) concentration of arils and peel of pomegranate (Punica grauatum) 'Malas Saveh' were determined. The fruits were immersed in distilled water and two CaCl 2 concentrations (135 and 270 mM) for 5 and 10 minutes. The peel Ca concentration of treated fruits significantly increased after 2 months storage, but the arils Ca concentration was not affected with different treatments. Chilling injury (CI) symptoms appeared after 2 months of storage. Postharvest CaCl 2 treatment limited the intense of peel CI symptoms such as browning and pitting but it had no significant effects on internal symptoms especially on segment separating thin layer browning. Treated fruits with 135 and 270 mM CaCl 2 reduced the ion leakage of peel up to 27 and 29%, respectively.

Pomegranate (Punica granatum L.) is rich in bioactive compounds such as phenolics and anthocyanins with proven antioxidant activity in vitro and in vivo. However, pomegranates are considered as perishable commodities with severe storability problems due to their sensitivity to developing chilling injury symptoms when they are stored at low temperatures. These symptoms are manifested by skin browning, surface pitting and desiccation and accompanied by increases in electrolyte leakage leading to quality losses and reduced shelf-life. In this chapter, an overview of the chilling injury incidence and its possible minimization throughout appropriate post-harvest treatments is provided, with special emphasis on some innovative tools such as the natural compounds methyl jasmonate and methyl salicylate. These treatments reduced chilling injury and enhanced the content of bioactive compounds and the total antioxidant activity of the arils along storage leading to fruit with enhanced phytochemicals and increased health-beneficial properties to consumers.