Effects Of Coupling Of Light Quality And Zinc Fertilizer On Quality And Zinc Accumulation Of Lettuce

Abstract:Light quality and nutrient solution are important environmental factors in growth and development of vegetables,which has an important influence on the distribution of vegetable assimilate and quality formation.The effects of different coupling treatments of light quality and Zn concentration on lettuce growth,quality,antioxidant capacity,antioxidant enzyme activity and mineral element accumulation were studied in this paper.Three levels of Zn are:(1)ordinary Zn concentration(7.65×10-4mmol/L Zn2+),(2)5-flod Zn concentration(3.82×10-3mmol/L Zn2+),and(3)10-flod concentration(7.65×10-3mmol/L Zn2+);three light quality levels are:(B)4B/1R,(M)1B/1R,(R)1B/4R;to determine the concentration of light quality and nutrient solutions suitable for Zn-rich lettuce production in plant factories.The main results are as follow:1.The effects of light quality and Zn treatment on the biomass and photosynthetic pigment content of lettuce were significant.Red light-based composite light and 10-flod Zn concentration treatment can promote the development of lettuce roots,improve the absorption of moisture and nutrients,so as to speed up the synthesis of photosynthetic pigments and enhance the photosynthetic capacity of lettuce,and then the vegetative growth of lettuce is accelerated.The lettuce has biggest biomass and photosynthetic pigment content under R3 treatment,and with the increase of the proportion of red light and Zn concentration increases.2.Different nutritional qualities have different responses to light quality and Zn treatment.The biggest content of Vc and soluble protein in B3 treatment,highest soluble sugar content under R3 treatment,lowest nitrate content in treatment B3,and highest free amino acid content under B2 treatment.Soluble sugar content increases with the proportion of red light improve.However,increased proportions of blue light can accelerate the synthesis of Vc,soluble protein,free amino acid and even nitrate degradation.The increase of Zn concentration can not only favors the accumulation of Vc,soluble protein,free amino acid and soluble sugar,but also promotes the metabolism of nitrate.3.Both light quality and Zn treatment have regulatory effects on antioxidant ability and antioxidant enzyme activity of lettuce.The proportion of blue light in the composite light increases,which can promote DPPH free radical scavenging rate,the antioxidant capacity of FRAP,the content of polyphenols and flavonoids,even the activity of POD and CAT.With the increase of Zn concentration,both antioxidant capacity and antioxidant enzyme activity have increased in varying degrees.The lettuce under B3 treatment,has the biggest DPPH free radical scavenging rate and FRAP antioxidant capacity,the highest polyphenols and flavonoids content,the strongest POD and CAT activity.4.Due to the red light-based compound light hold the biggest biomass of lettuce,so it has a relatively low content of elements.However,the specific trends of N,P,K,Ca,Mg content changes with light quality and Zn concentration are unknown.The increase of the proportion of red light and Zn concentration,which are beneficial to the accumulation of N,P,K,Ca,Mg and Fe,Mn,Zn.The accumulation amounts of N,P,K,Ca,Mg and Fe,Mn,Zn in shoots of lettuce are the biggest under treatment R3.5.The study shows that B3 treatment contributes to the improvement of quality and antioxidant capacity,and R3 treatment can promote the increase of yield and element accumulation,which can be used as a reference scheme for Zn-rich production in plant factories.