Effects Of Light Conditions And Nutrient Solution Concentration On The Content Of Potassium In Lettuce

Low-potassium vegetable as a new choice for choric kidney disease?CKD?patients is seldom in China.The effect of light conditions and the potassium-restriction treatments in nutrient solution on the potassium content,yield,nutritional quality,and antioxidant capacity of lettuce?Lactuca sativa L.?were studied,the light conditions include two light quality?8R1B and 1R1B?and two light intensity(300,450?mol·m^-2·s^-1).The results showed that:1.The influence of different light environments on the growth of lettuce was different.In general,a high proportion of red light?8R1B?contributes to higher water content and fresh weight of shoot than 1R1B.2.The influence of different light environments on the quality of lettuce was different.The concentration of photosynthetic pigments,soluble protein,free amino acid and ascorbic acid as well as the DPPH radical scavenging rate,FRAP value,content of polyphenol and flavonoid in lettuce were both higher in 1R1B than 8R1B.In general,a high proportion of blue light?1R1B?promote the accumulation of photosynthetic pigments,soluble protein,free amino acid and ascorbic acid,and enhance the antioxidant activity of lettuce.3.The effect of different light environments on the potassium content in lettuce was different.Under potassium condition,the decrease of potassium content in lettuce was higher in 450?mol·m^-2·s^-11 than 300?mol·m^-2·s^-1.Under the control,a high proportion of blue light?1R1B?showed a stronger inhibition for the accumulation of potassium in lettuce.4.The influence of potassium-restricton treatments on the growth of lettuce depends on the light conditions.Under 1R1B-300,1R1B-450 and 8R1B-450 light condition,the growth of shoot do not be negatively impacted by K restriction in nutrient solution.5.The quality of lettuce was improved by potassium-restricton treatments.Under1R1B-450,8R1B-300 and 8R1B-450 treatment,the content of soluble protein and ascorbic acid increased in the potassium-restricton treatments,and the DPPH radical scavenging rate,FRAP value,content of polyphenol and flavonoid in lettuce also increased.6.Potassium content in lettuce decreased significantly under potassium-restriction treatments,and decreased more with the potassium supply decrease.Potassium content in the treatment of 0Mm K in two weeks before harvest was the lowest,which decreased about 66.6%.However,the content of sodium,magnesium and calcium in lettuce increased in potassium-restriction treatments.On the whole,the high proportion of blue light?1R1B?was contribute to the improvement of nutrition and antioxidant activity of lettuce.In 450?mol·m^-2·s^-11 light intensity,lettuce could maintain the normal growth under potassium-restriction treatments.And the treatment of 0Mm K in two weeks before harvest was more suitable ways to reduce potassium content of lettuce.Therefore,the most suitable environmental condition for the cultivation of low-potassium lettuce is the combination of 1R1B-450?mol·m^-2·s^-1light and potassium-restriction treatment in two weeks before harvest.