Effects Of Different Light Qualities On The Growth Of Gynura Bicolor

Light is one of the important factors for plant growth,involved in the seed germination,growth,development and flowering.Light mainly affects plants growth in the form of light quality,intensity,photoperiod.Among these dimensions,light quality is the most important one.Therefore,research of the effects of different light quality on the growth of different plant is of great significance.Plant factory is considered to be the advanced stage of the development of agricultural facilities.Plant factory can precisely control the growth environment of plant with its highly intensive technology and achieve the production process which is short cycled,high yield,high quality,and recyclable.Now more and more countries in the world begin to develop plant factory technology.As a new type of light source,LED lights has the advantage of a smaller volume,low heat output,high efficiency and accurate spectrum when compared with traditional light sources.Therefore,LED lights have become the most popular choice of light source in most plant factories.In this thesis,Gynura Bicolor was chosen as the experimental material,which is edible and can be used as medicine as well.Red,blue,green LED lights were used as the light source of which wavelengths were 660nm,446nm and 525nm respectively.There were 2 sets of experiments(written as Experiment 1 and Experiment 2 in the following)in this thesis,in which light quality was the only variation.Light treatments were set as follows(the light treatments ratio were set as Red LED:Green LED:Blue LED):(1)10:0:0,(2)7:0:3,(3)5:2:3,(4)3:2:5,(5)3:0:7,(6)0:0:10,and the fluorescent lamp was used as the control.The 6 treatments are written as Pure Red,R7B3,R5G2B3,R3G2B5,R3B7,Pure Blue in the following.Growth parameters and 4 biochemical parameters of Gynura Bicolor seedlings were measured after 28 days of growing.Experiment 1 aimed to find the effects of different light qualities on the growth and quality of Gynura Bicolor.The material of Experiment 2 were the Gynura Bicolor seedlings which had been raised for 28 days in Experiment 1 and the Gynura Bicolor seedlings in Experiment 1 were exchanged in the following ways:1st with 6th treatment,2nd with 5th treatment,3rd with 4th treatment(Other factors remain the same).Experiment 2 aimed to find if the effects of different light on the growth and quality of Gynura Bicolor were reversible.Main results were as follows:(1)Effects of different light qualities on the growth of Gynura Bicolor seedlings.Under the same light intensity,same photoperiod,same humidity and same temperature,the red and blue mixed light remarkably increased the growth parameters of Gynura Bicolor seedlings except for the seedling height;Pure red light remarkably increased the fresh weight and hypocotyl length of Gynura Bicolor seedlings but restrained the dry weight and stem diameter;Pure blue light had inverse effects on fresh weight and dry weight of Gynura Bicolor seedlings,it restrained the whole seedling fresh weight and upper-ground part fresh weight,but increased the whole seedling dry weight and upper-ground part dry weight.It also increased the root fresh weight but restrained the root dry weight.Besides it remarkably restrained the stem diameter and hypocotyl length.Green light increased the dry weight and restrained the fresh weight of Gynura Bicolor seedlings,which was contrary to the effects of red light.Also the effects of green light on the stem diameter and hypocotyl length of Gynura Bicolor seedlings depended on the ratio of the red light and blue light in the treatment.The Gynura Bicolor seedlings that was raised in R5G2B3 treatment had the largest hypocotyl length,while R3G2B5 restrained the hypocotyl length.Similarly,R5G2B3 increased the stem diameter while R3G2B5 restrained the stem diameter.For the height of Gynura Bicolor seedlings,only pure red light increased this parameter,other treatments in Experiment one restrained the height of Gynura Bicolor seedlings.(2)Effects of different light qualities on the quality of Gynura Bicolor seedlings.Under the same light intensity,same photoperiod,same humidity and same temperature,the red and blue mixed light remarkably increased the anthocyanin content,soluble protein content and soluble sugar content,meanwhile restrained the carcinogen nitrate nitrogen content,which suggested that the quality of Gynura Bicolor seedlings could benefit form the red and blue mixed light.Pure red light increased the anthocyanin content,soluble sugar content,meanwhile had few effects on soluble protein content and nitrate nitrogen content.Pure blue light remarkably increased the anthocyanin content,soluble protein content,meanwhile increased the nitrate nitrogen content.The content of soluble sugar of Gynura Bicolor seedlings was remarkably lower than that of control group.Green light could increase the soluble protein content.The effects of same green light mixed with red and blue light depended on the ratio of the red and blue mixed light.R3G2B5 treatment increased anthocyanin content and soluble sugar content of Gynura Bicolor seedlings,but the nitrate nitrogen content was higher than that of control group.R5G2B3 treatment increased the soluble sugar content and decreased the nitrate nitrogen content,but the anthocyanin was also restrained.(3)The reversibility of effects of different light qualities on the growth of Gynura Bicolor seedlings.The conclusions of Experiment 2 are as follow:The effects of pure red light and pure blue light on the whole seedling fresh weight,upper-ground part fresh weight,whole seedling dry weight,upper-ground part dry weight,seedling height,stem diameter and hypocotyl length of Gynura Bicolor seedlings were reversible;The effects of R7B3 treatment and R3B7 treatment on the fresh weight,dry weight,seedling height and hypocotyl length of Gynura Bicolor seedlings were reversible.The effects of R5G2B3 treatment and R3G2B5 treatment on the dry weight,seedling height and hypocotyl length of Gynura Bicolor seedlings were reversible.(4)The reversibility of effects of different light qualities on the quality of Gynura Bicolor seedlings.The effects of pure red light and pure blue light on the anthocyanin content,soluble sugar content,soluble protein content and nitrate nitrogen content of Gynura Bicolor seedlings were reversible.The effects of R7B3 treatment and R3B7 treatment on the anthocyanin content,soluble sugar content and nitrate nitrogen content of Gynura Bicolor seedlings were reversible.The effects of R5G2B3 treatment and R3G2B5 treatment on the anthocyanin content,soluble sugar content,soluble protein content and nitrate nitrogen content of Gynura Bicolor seedlings were reversible.This research suggested that red and blue mixed light is suitable for the growth of Gynura Bicolor seedlings.Among all the 7 treatments,70%blue light and 30%red light was the best combination.The growth parameter and biochemical parameter of Gynura Bicolor seedlings were increased when the Gynura Bicolor seedlings was illuminated by R7B3 light,which is of great significance to the quantitative production and relative healthy product development of Gynura Bicolor seedlings.Besides,this experiment also found that the effects of different light qualities on Gynura Bicolor seedlings are reversible,which offered a new horizon of searching for the best light qualities for different growing stages of Gynura Bicolor seedlings.Through the reversibility of the effects of different light qualities on the Gynura Bicolor seedlings,the Gynura Bicolor seedlings could achieve a better quality.