| This research mainly established a high-efficiency farming mode of an agricultural fish-flower(mint)symbiosis closed-loop system in the glass glasshouse,which aims to use fish excrement to provide nutrition for mint.Mint can purify water quality and beautify the glasshouse environment by absorbing excessive ammonia nitrogen and nitrite in the water.Through the detection of the light environments inside and outside the glasshouse,it was found that the mint can not get enough light in the system due to space obstructions and other problems when the light passes through the glasshouse.Therefore,in order to solve this problem,four kinds of different light types(red light(R),blue light(B),far red light(FR),red and blue light(BR))are used to supplement the light on the mint,respectively.Compared with the control(i.e.,no supplementary light),we studied the changes of water quality,physiological characteristics,quality of different parts,enzyme activity and volatile components in the fish-flower(mint)symbiosis closed-loop system under different supplementary light.The main results are shown below:(1)The effects of different light types on the water quality.The results showed that the content of ammonia nitrogen and nitrite had an overall downward trend,and the content in the control(CK)group was slightly higher than the other supplementary light groups,and the content of nitrite decreased the most by supplement the red and blue light(BR);the content of phosphate of each supplementary light group was higher than the control(CK)group,and the content of phosphate with far-red light(FR)was 0.03mg/L,which overall was slightly lower than the control(CK)group.In addition,the pH tends to be stable in the range of 7.8～8.2 because of stable environmental glasshouse.(2)The effects of different light types on physiological characteristics of mint.Compared with the control(CK),supplementary light can increase the fresh weight and dry weight of mint.The fresh weight on the plate and under the plate by the red and blue light(BR)was the largest at 80g;the dry weight on the board by red and blue light(BR)was the largest at 8.82g and the dry weight under the board by red light(R)was the largest;the growth of plant height and root length of mint with the treatment of red and blue light(BR)was best;the stem thickness was best by the treatment of blue light(B)and the maximum stem thickness was 3.91mm.Red and blue light(BR)and blue light(B)were more conducive to promote the growth of mint plant height,stem thickness and root length.Different treatments of supplementary light significantly increased the number of leaves,leaf length,leaf width and leaf area;red and blue light(BR)was most conducive to the increase of chlorophyll,anthocyanin,and carotenoid content.The water content of mint was not significantly different with the increasing of supplementary light time.(3)The effects of different light types on the quality of different parts of mint and the activity of antioxidant enzymes.The contents of ash,crude protein,crude fat,and crude fiber were significantly higher than those in the control(CK)group.The quality of mint was comprehensively evaluated through correlation analysis and principal component analysis.The quality of the mint roots with the treatment of the red and blue light(BR)had the best quality.The quality of the stems and leaves with the treatment of blue light(B)had the best quality.The activity of SOD enzyme is the highest under the treatment of red and blue light(BR),reached 138.33 and 140.98 U·g-1·min-1,respectively.The POD enzyme activity was the highest under the red and blue light(BR),and the activity of the POD enzyme was the highest in the red and blue light(BR).The difference between the far-red light(FR)and control(CK)was not significant.There was no significant difference in CAT activity among the supplementary light groups.In general,for the three antioxidant enzyme activities of mint,the root activity was slightly greater than the stem and leaf activity.Under the same kind of treatment of supplementary light,its enzyme activity will increase with the prolongation of supplementary light time.(4)The effect of different light types on the volatile components of different parts of mint,mainly adopted gas chromatography-ion mobility spectroscopy(GC-IMS)technology.In the root,a total of fifteen kinds of volatile substances including three kinds of alcohols,four kinds of ketones,five kinds of aldehydes,two kinds of esters,one kind of terpenes.The peak volume was higher for the red and blue(BR)light treated n-butanol,n-hexanal,etc.,the red light(R)treated valeraldehyde,and far red light(FR)treated butyraldehyde,ethyl acetate,etc.In the stem,a total of twenty-five kinds of volatile substances were identified,including eleven kind of alcohols,four kind of ketones,four kind of aldehydes,three kind of esters,two kinds of terpenes and one kinds of pyrazine compound.The peak one was higher for the red and blue(BR)light treated phenethyl alcohol,1-octene-3-ol,etc.,and the far-red light(FR)treated valeraldehyde,ethyl acetate,etc.A total of thirty-seven volatile substances were identified in the leaves,including twelve kinds of alcohols,eleven kinds of ketones,six kinds of aldehydes,two kinds of alkenes,four kinds of esters,and two kinds of pyrazines.Among them,the peak volumes of limonene and α-pinene under the treatments of blue(B),red-blue combination(BR),and far-red light(FR)were higher than other light treatments.By the principal component analysis,there was a great difference between the treatments of four supplementary light.The difference between the initial stage and the final stage was also large,which indicated that there were differences in volatile components between different treatments of supplementary light on the root,stem and leaf.The results showed that the GC-IMS technical analysis can better judge the effects of different light qualities on the volatile components of peppermint roots,stems and leaves.To sum up,this study mainly used different light types to supplement light in the fish-flower(mint)symbiosis closed-loop system established in a glasshouse.The results showed that supplementary light can significantly promote the growth,quality and quality of peppermint.Through the identification and analysis of the volatile components of mint with the treatment of supplementary light,it was found that the volatile components of different treatment of supplementary light were very different.The above research can provide scientific and reasonable advice and basis for the future processing of mint in food flavors,condiments,mint drinks or mint feed,and so on. |
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