Effect Of Red And Blue Light Quality On Essential Oil Of Lemon Balm

Lemon Balm?Melissa officinalis L.?is a medicinal and edible herb of Melissa which has a long history of cultivation and application in Mediterranean.The essential oil of Lemon Balm is popular in many fields such as food processing,cosmetics,perfume and so on,and it is also play a great role in traditional medicine with excellent bioactivity.But it is costly as an unsatisfied yield of essential oil.Ultraviolet irradiation is frequently used to improve the essential oil yield of herb around the world which will make a latent harm to the gardeners and plants.Thus,it is meaningful to find out a way to increase the essential oil of Lemon Balm mildly.The study is combined with two parts.Lemon Balm was cultured under artificial light in door to evaluate the effect of red and blue light at first.Then an efficient light with specific color was screened out for the next test.Light supplement in different wave length base on the specific color was served to the Lemon Balm to evaluate its effectiveness.Three kind of LED with different red to blue ratio?R2B1?R:B=2:1?,R1B1?R:B=1:1?,R1B2?R:B=1:2??was used as test treatment while a white light was used as control on100?mol?m^-2?s^-1.Content of essential oil was checked at the 30 days.And the extended test was based on the blue color with four treatment in different wave length:665nm?Red?,400nm?B400?,430nm?B430?and 460nm?B460?on 50?mol?m^-2?s^-1 last 8 hours per day.And a blank group was set without artificial light.All group took a 50%shade.Lemon Balm was cultured in a greenhouse last for 40 days.?1?Content of essential oil increase with the increasing light ratio of red to blue in test1.1R2B has the greatest essential oil content with an increment of 155.29%compared to the control.Ratio of hemiterpene,monoterpenes and oxygenated monoterpenes contained in the oil almost has the same trend with the essential oil yield while the sesquiterpenes and oxygenated sesquiterpenes reverse,which can draw a conclusion that blue light can promote the accumulation of monoterpenes as red light done the same to sesquiterpenes.?2?In the light supplement test,essential oil content from the Red group is inhibited heaviest.As time went by,400nm and 460nm supplement show a great increase.Especially a 40-day treatment of the 460nm can promote the content of essential oil well,so as the yield.Ratio of monoterpenes grow with the increasing of wave length of blue light,and the oxygenated sesquiterpenes show a reverse under a 20-day treatment.When it last for 40days,ratio of hemiterpene,sesquiterpenes and oxygenated sesquiterpenes decrease with the increasing of blue light wave length.In addition,the blue groups?B400-B460?is positive toward the photomorphogenesis of Lemon Balm in which the 430nm perform excellent as an increasing of shoot weight and inhibition of internodal distance.Besides,supplement of400nm for 20 days can race the DPPH free radical scavenging capacity,polyphenol and flavonoid content up while 460nm can promote the FRAP remarkably.In conclusion,supplement of blue light is efficient to the photomorphogenesis and essential oil content of Lemon Balm and so as the anti-oxidant power in it,in which the 430nm contribute most to build up the plant and the 460nm promote the essential oil while the 400nm enhance the anti-oxidant power.