Pomegranate is a subtropical and chilling sensitive fruit. In this study, the effects of malic acid (50 and 100 mM) and oxalic acid (5 and 10 mM) on quality properties of pomegranate during cold storage (2 ℃) were investigated. The lowest weight loss was observed in fruit treated with 50 mM malic acid. Malic acid had positive effects on color parameters (L*, a*, and b*) of pomegranate at low temperature. Organic acid treatments reduced chilling injury, malondialdehyde, and hydrogen peroxide and increased catalase activity. The lowest activity of polyphenol oxidase and peroxidase was observed in 5 mM oxalic acid-treated fruit. On the other hand, fruit treated with 50 mM malic acid showed the maximum ascorbic acid and citric acid content. The most antioxidant activity was found in fruit treated with 5 mM oxalic acid and 50 mM malic acid. Also, all treatments except 10 mM oxalic acid and 100 mM malic acid resulted in higher titratable acidity than control fruit. Overall, 50 mM malic acid and 5 mM oxalic acid were the most effective for preserving the quality of pomegranate fruit at low temperature.

Water deficit is one of the most important factors in reducing medicinal plants’ yield. Origanum majorana L. grows in the some regions of world and it is cultivated for consumption and pharmaceutical purposes. In order to study the effects of methyl jasmonic acid (MeJA) on O. majorana L. under limited irrigation conditions, a factorial experiment was performed as a complete randomized design with three replications. Experimental factors including different limited irrigation conditions such as keeping the pots at field capacity during the experiment (control), irrigation pots in 75 % field capacity (mild limited irrigation), and irrigation plants in 50 % field capacity (moderate limited irrigation), and spraying treatments include 100 μM MeJA and control with water. At flowering stage, fresh weight, dry weight, and essential oil percentage (EO %) and yield, and essential oil composition were measured. Results indicated that moderate limited irrigation decreased plant weight and essential oil yield compared to the control. However, both mild and moderate limited irrigations increased EO % compared to the control. Foliar spray of MeJA improved growth parameters such as O. majorana L. fresh and dry weight just under mild limited irrigation conditions, while under moderate limited irrigation application of MeJA could not significantly change these parameters. Under mild limited irrigation conditions, MeJA causes significant reductions of 16.9 and 12.0 % in EO % and yield, respectively. Although limited irrigation did not have a significant effect on all of the O. majorana L. essential oil components, MeJA application changed O. majorana L. essential oil composition. With an increase in the limited irrigation level, MeJA application diminished the content of monoterpene hydrocarbons components from 20.56 to 18.21 % and increased oxygenated monoterpenes from 62.73 to 65.44 %. Results of this study revealed that MeJA could alleviate drought stress damages by stimulating oxygenated monoterpenes production and, therefore, could improve essential oil production under water stress conditions.