Effects Of Exogenous Selenium Concentration And Light Intensity On Growth,Quality And Selenium Content Of Lettuce

Light is one of the necessary conditions for plant growth,light environmental control is an important technogy of facilities and horticultural production.Selenium is a beneficial element of the human body,and selenium-rich vegetables are an important source of human selenium.The appropriate light environment and the regulation of exogenous selenium both can promote the quality of vegetables and improve the quality and effective selenium content.Previous studies on selenium-rich vegetables are mostly conducted of exogenous selenium or light environment treatment,while the two factors integrated treatment of vegetables are less reported.In the rapid development of the facilities of horticultural and plant plants,the multi-factor system for the study of vegetable selenium-rich production technology enjoys greart popularity.In this experiment,under the conditio n of 4: 1,the different concentrations of exogenous selenium(Na2Se O3 0.05 mg/L,0.20 mg/L)were added to the lettuce as the material under the condition of plant plant production.,0.35 mg/L,0.5 mg/L),the growth and development of lettuce,nutrient quality,nutrient uptake and selenium absorption and transformation were studied.Further,on the basis of exogenous selenium concentration of 0.20 mg/L,(125μmol·m-2·s-1,200μmol·m-2·s-1,300μmol·m-2·s-1,425μmol·m-2·s-1,575μmol·m-2·s-1)were used to study the development of lettuce,quality,nutrient uptake and selenium absorption.The main findings are as follows:1.The effects of different concentrations of selenium on growth,quality and selenium content(1)The effects of different concentrations of selenium on growth and development of lettuce.Low concentration of selenium(0.05-0.35 mg/L)could significantly promote the growth of lettuce compared with non-exogenous selenium(CK)treatment,while highconcentration of selenium(0.5 mg/L)inhibited lettuce growth.There was no significant difference in photosynthetic pigment content between leaves of lettuce with different concentrations of selenium.With the increase of exogenous selenium concentration in nutrient solution,the root activity of lettuce increased first and then decreased,and reached the maximum at 0.20 mg/L.(2)The effects of different concentrations of selenium on lettuce quality.With the increase of exogenous selenium concentration in nutrient solution,the contents of soluble protein,free amino acid,Vc and soluble sugar in lettuce were increased first and then decreased,and the content of exogenous selenium reached the maximum value under treatment of 0.20 mg/L.Exogenous selenium concentration of 0.35 mg/L treated Vc and soluble sugar content reached the maximum.The antioxidant capacity of flavonoids,polyphenols and FRAP of lettuce was the highest under the treatme nt of exogenous selenium 0.05 mg/L.(3)The effects of different concentrations of selenium on the absorption of selenium and beneficial mineral elements.Compared with CK,selenium promoted the uptake and accumulation of total calcium,magnesium,zinc and iron in the upper part of lettuce,and reduced the absorption and accumulation of total phosphorus.When the exogenous selenium was 0.35 mg/L,all the mineral elements accumulated.The content of total selenium,organic selenium and organic selenium were the highest in exogenous selenium 0.2 mg/L.2.The effects of different light intensities on growth,quality and selenium content(1)The effects of different light intensities on lettuce growth.With the increase of light intensity,the number of leaves and lettuce of lettuce increased gradually,and the light intensity was increased by 300μmol·m-2·s-1,425μmol·m-2·s-1 and 575μmol·m-2·s-1 treatment was not significant.Lightweight 575μmol·m-2·s-1 treated lettuce leaves were burned.Thus,light intensity of 300μmol·m-2·s-1 is the best light intensity to promote lettuce growth.With the increase of light intensity,the photosynthetic pigment content of lettuce leaves showed a decreasing trend.(2)The effects of different light intensity on lettuce quality.With the increase of lightintensity,the content of free amino acid and soluble sugar in lettuce gradually increased,while the Vc content decreased gradually.The nutrient quality of lettuce was the highest under 300μmol·m-2·s-1 light intensity.Under the light intensity of 425μmol·m-2·s-1,the antioxidant capacity of lettuce was the highest.(3)The effects of different light intensities on the absorption of selenium and beneficial mineral elements.The contents of total potassium,calcium,sulfur,iron and zinc in the upper part of sesame-rich lettuce were decreased with the increase of light intensity.Under the treatment of light intensity of 300μmol·m-2·s-1,the total nitrogen,phosphorus,potassium and calcium,sulfur,zinc and iron accumulation to reach the maximum.The content of total selenium,organic selenium and organic selenium in selenium-rich lettuce increased first and then decreased with the increase of light intensity,a nd r ea c hed t he ma xi m um at 300μmol·m-2·s-1.In summary,the exogenous selenium concentration of 0.20 mg/L,lettuce nutrition quality,organic selenium content and conversion rate of lettuce were the highest.When the light intensity was 300μmol·m-2·s-1,the biomass of selenium-rich lettuce,the accumulation of mineral nutrient elements,the highest content of organic selenium and the conversion rate were the highest.Therefore,the exogenous selenium concentration in t he nutrient solution was 0.20 mg/L and the light intensity of 300μmol·m-2·s-1 was the best combination of selenium selenium production in the vegetable plant under the condition of common red and blue light ratio of 4: 1.