The Effect of Temperature on Growth, Oil Yield and Oil Quality of Japanese Mint

Field studies of factors affecting yield and composition ofJapanese mint oil are confounded by interacting environmentalagencies. The effect of temperature, separated from other influences,was examined on Japanese mint (Mentha arvensis L. var. piperascensHolmes) in the naturally lit controlled environment Phytotron,Canberra, Australia. The So Wo I variety of Japanese mint wasgrown under 12 treatments consisting of four day and three nighttemperatures. Maximum leaf, stem and root dry matter was producedunder 30 °C day temperatures, regardless of night temperature,but maximum stolon growth occurred at 20 °C temperatures.Generally, oil yield could be estimated by determining dry matterof above ground parts, but number of oil glands on the leavesdid not provide a reliable indication of oil yield. Differenttemperature treatments did not appear to affect greatly thepercentage of menthol, an important component of the oil. Underfield conditions, maximum yield of Japanese mint oil has beenfound to occur during flowering. This close relationship betweenoil yield and flowering did not occur under extremes of temperature.Although 30 °C was found to be the optimum day temperaturefor oil yield in this experiment where only one harvest wasmade, it is possible that where multiple harvests are conducted,a lower optimum temperature might be found, since the highertemperature was detrimental to dry matter reserves in the stolons. Mentha arvensis L. var. piperascens Holmes, Japanese mint, temperature, controlled environment, menthol, methone, essential oil, flowering     

The Effect of Age and Location of Leaf on Quantity and Quality of Japanese Mint Oil Production

Leaves of debranched Japanese mint (Mentha arvensis L., subsp.haplocalyx Briquet var. piperascens Holmes) were marked to allowsubsequent identification for age. Leaves of different age groupswere distilled for determination of quantity and quality ofoil. Most of the oil and its principal component, menthol, weresynthesized during the first 2 weeks of growth, while menthoneand the a-pinene percentage composition of the oil declinedwith age after 2 weeks. A significant decrease in percentageoil content occurred in older leaves indicating that leaf lossthrough senescence caused less loss of oil than of dry matter.Proportion of young to old leaves had a significant effect onoil composition. This is believed to be the first report onoil composition of leaves from single plants of Japanese mint.     

The Effects of Solar Radiation on Plant Growth, Oil Yield and Oil Quality of Japanese Mint

Plants of Japanese mint (Mentha arvensis L. subsp. haplocalyxBriquet var. piperascens Holmes) were grown under 100, 64, 49and 28% conditions of prevailing radiation for 10 weeks, withharvests at 4, 6.8 and 10 weeks. Measurements were made on plantgrowth, yields of essential oil and chemical composition ofoil. The greatest morphological responses to increased shading intensitywere increases in stem length and leaf area. Little responseto shading was shown by mean relative growth rate (RGR) or meannet assimilation rate (NAR) while that of mean leaf area ratio(LAR) was marked. No significant differences in oil yield werefound among different treatments at the final harvest nor werethere great differences in amounts of menthol and menthone,two important constituents of Japanese mint oil. The experiments indicate that, within the experimental limitsimposed, Japanese mint tends to compensate in growth and oilproduction for shading effects. This work may also explain thedifferent and sometimes contradictory results reported in theliterature on the effects of shading on mint oil production