The combined and single effect of salinity and copper stress on growth and quality of Mentha spicata plants

Copper is essential for plant growth, but in excess may cause adverse effects on plant physiology. Harmful effects are also caused by plant exposure to salinity (NaCl) due to the excessive use of fertilizers, soil degradation and/or the quality of the water used for irrigation. The impact of single and combined salinity (Sal) and copper (Cu) stress on spearmint metabolism were studied in hydroponics. Spearmint plants (Mentha spicata L.) were subjected to salinity stress (150 mM NaCl) and/or excessive Cu concentration (60 μM Cu) via the nutrient solution. Not only Sal and Cu, but also their combination suppressed plant growth by decreasing plant biomass, root fresh weight and plant height. Chlorophyll content decreased mainly for the combined stress treatment (Sal + Cu). Polyphenols and antioxidants (FRAP, DPPH, ABTS) increased in single stress treatments (Sal or Cu), but decreased in the combined stress (Sal + Cu). The application of Sal or Cu stress decreased Zn, N and K (leaves), K, Ca, P and Mg (roots) content. Copper application increased Ca and Mg in leaves. In conclusion, salinity stress and Cu exposure may change the primary metabolic pathways in favor of major volatile oil components biosynthesis, resulting in significant changes of essential oil yield and composition.

Physiological and biochemical attributes of Mentha spicata when subjected to saline conditions and cation foliar application

Marginal water, including saline water, has been proposed as an alternative source of irrigation water for partially covering plant water requirements due to scarcity of adequate water supply in hot arid and semi-arid areas, such as those usually found in the Mediterranean basin. In the present study, spearmint plants (Mentha spicata L.) were grown in a deep flow hydroponic system under saline conditions, namely 0, 25, 50, and 100 mM NaCl. Moreover, foliar application of specific cations (K, Zn, Si) was tested as a means for alleviation of salinity stress under a plant physiological and biochemical approach. The results indicated that the highest salinity level of 100 mM NaCl severely affected plant growth, photosynthetic rates, leaf stomatal conductance, content of total phenolics and antioxidant status, while low to moderate salinity levels (25-50 mM NaCl) did not significantly affect plant growth and biochemical functions. In addition, leaf potassium and calcium accumulation decreased in saline-treated plants. Cations foliar application had small to no effect on plant growth, although it increased antioxidant activity and detoxified oxidative stress products/effects, through the increased enzymatic activities and proline accumulation. The present results have demonstrated that spearmint could be considered as a salinity tolerant species which is able to grow successfully under moderate salinity levels, while cation enrichment through foliar sprays was proved as a useful means to alleviate the stress effects caused by high salinity.

Chemical composition, antioxidant, antimicrobial and Antiproliferative activities of essential oil of Mentha spicata L. (Lamiaceae) from Algerian Saharan atlas

BACKGROUND

Mentha spicata (M. spicata) is a member of Lamiaceae that spreads mainly in the temperate and sub-temperate zones of the world. It is considered as a rich source of essential oils, which is widely used in pharmaceutical industries and food production. The objectives of the current study were to evaluate chemical composition, antioxidant, antimicrobial and antiproliferative activities associated with the essential oil of M. spicata cultivated in Algerian Saharan Atlas.

METHODS

The aerial parts of M. spicata were subjected to hydrodistillation to produce the oil. Chemical identification of the oil composition was conducted by GC and GC-MS analyses. The antioxidant activity of the hydrodistilled oil was studied using DPPH, ABTS radical scavenging and ferric-reducing power assay. Antimicrobial potential was characterized against two microorganisms, signifying Gram positive, and Gram negative bacteria, and one Candida species. The microdilution method was employed to determine the minimum inhibitory concentration (MIC). The oil's antiproliferative effects against three human tumor cell lines were also investigated using the MTT assay, and the toxic doses that yielded 50% reduction of cell viability (LD50) were reported.

RESULTS

Chemical analysis of the essential oil composition revealed 44 unique compounds with oxygenated monoterpenes (67.2%), followed by monoterpene hydrocarbons (20.8%), as the most abundant chemical components. Essential oil of M. spicata demonstrated moderate antioxidant activities as well as moderate to weak antimicrobial activities with best susceptibility observed for Gram positive bacteria towards the oil. In addition, anticancer activities that are associated with the oil against three human cancer cell lines were observed with LD50 values of 324 μg/mL, 279 μg/mL, 975 μg/mL against T47D, HCT-116 and MCF-7 cell lines, respectively.

CONCLUSION

The results suggest that M. spicata essential oil may have potential value as a bioactive oil, for nutraceutical and medical applications, with its antioxidant, antimicrobial and antiproliferative activities.

Weed interference with peppermint (Mentha x piperita L.) and spearmint (Mentha spicata L.) crops under different herbicide treatments: effects on biomass and essential oil yield

BACKGROUND

'Minor crops' such as spearmint and peppermint are high added value crops, despite the fact that their production area is comparably small worldwide. The main limiting factor in mint commercial cultivation is weed competition. Thus, field experiments were carried out to evaluate the effects of weed interference on growth, biomass and essential oil yield in peppermint and spearmint under different herbicide treatments.

RESULTS

The application of pendimethalin and oxyfluorfen provided better control of annual weeds resulting in higher crop yield. Additionally, when treated with herbicides both crops were more competitive against annual weeds in the second year than in the first year. All pre-emergence herbicides increased biomass yield, since pendimethalin, linuron and oxyfluorfen reduced the density of annual weeds by 71-92%, 63-74% and 86-95%, respectively. Weed interference and herbicide application had no effect on essential oil content; however, a relatively strong impact on essential oil production per cultivated area unit was observed, mainly due to the adverse effect of weed interference on plant growth.

CONCLUSION

Considering that pendimethalin and oxyfluorfen were effective against annual weeds in both spearmint and peppermint crops, these herbicides should be included in integrated weed management systems for better weed management in mint crops. © 2017 Society of Chemical Industry.

Effect of distillation waste water and plant hormones on spearmint growth and composition

BACKGROUND

Distillation waste water (DWW) is a by-product from steam distillation of essential-oil crops; and currently, it is discharged into streams and rivers. The effects of DWW from 13 essential-oil crops, extracts from two alkaloid-containing species, and three plant hormones (methyl jasmonate, MJ; gibberellic acid, GA3; and salicylic acid, SA) were evaluated on productivity, essential-oil content and composition of spearmint (Mentha spicata L.) cv. 'Native'.

RESULTS

Spearmint plant height was increased by the application of GA3 and Melissa officinalis DWW but suppressed by the application of Rosmarinus officinalis and Tagetes lucida DWW. Generally, MJ, GA3 and M. officinalis and Mentha arvensis DWW increased dry yields. The concentration of L-carvone in the oil ranged from 550 g kg(-1) (with Monarda citriodora DWW) to 670 g kg(-1) (with T. lucida DWW). M. citriodora DWW reduced the concentration of L-carvone in the oil by 23% relative to the control.

CONCLUSION

Results suggest that DWW from essential-oil crops may affect monoterpene synthesis in M. spicata and, hence, may have a direct effect on the essential oil composition. DWW from essential-oil crops may be used as a growth promoter and modifier of the essential oil composition of spearmint.

Characterization of the harmful effect of olive mill wastewater on spearmint

In this study, changes in viability, biomass production, essential oil yield and essential oil composition of Mentha spicata L. (spearmint) exposed to olive mill wastewater (OMW) were investigated. Spearmint cuttings were sensitive to OMW and, after 6h of incubation in raw or diluted OMW, their viability was null. The short contact of raw OMW with mint cuttings caused an irreversible damage in rhizogenesis and shoots development. Roots were more sensitive to phytotoxicity than shoots. In a field essay, spearmint showed a good capability to recover when OMW was spread at 8 l m(-2) at the vegetative phase of growth (45 days after plantation). At this dose, a slight increase of mostly of the mint essential oil constituents was obtained. When the dose applied was 16 l m(-2), phytotoxicity was manifested by a high reduction of biomass and essential oil yield. The essential oil composition was also affected and a disappearance of many of mint essential oil constituents was observed with an increase of 59% for carvone, the major compound of spearmint essential oil. As far as we know, this is the first report on the effect of field application of OMW on an aromatic plant essential oil yield and composition.