Effects Of Different Nutrient Solution Ratios In Plant Factory On Growth And Nutritional Quality Of Brassica Rapa

Plant factories can artificially control environmental conditions and create suitable growth environment for plants.Nutrient solution is the core of plant factory,providing nutrients needed for plant growth.Brassica rapa（Brassica rapa L.）is a nutritious plant with high levels of glucosinolates,which can help prevent cancer and improve health.At present,brassica rapa has become one of the biggest vegetables in our market demand,and the traditional cultivation method can not meet people’s pursuit of quality already.At present,there are many researches on the formulation screening and improvement of hydroponic leaf vegetable nutrient solution,but there are few researches on the effect of different nutrient solution ratio on the growth and nutrient quality of brassica rapa Therefore,the effects of different nutrient solution concentrations and nitrate nitrogen concentrations on the growth and nutrient quality of brassica rapa were studied in this experiment,in order to provide theoretical basis and technical support for the formulation optimization of hydroponic nutrient solution of brassica rapa under plant factory conditions.The main research results were as follows:1.The effects of different nutrient solution concentrations on brassica rapa growth and photosynthetic indexes were significant.With the increase of nutrient solution concentration,the growth,biomass and water content of brassica rapa showed an overall upward trend,with the maximum value under T_2.5treatment.Chl a,Chl b and Chl（a+b）of brassica rapa showed a trend of first increasing,then decreasing and then increasing with the increase of nutrient solution concentration.Among them,Chl a,Chl b and Chl（a+b）under T_2.5treatment increased by 9.02%,7.37%and 8.52%,respectively compared with CK.The content of chlorophyll a/b in each nutrient solution was higher than CK.2.Different nutrient solution treatments affected the nutrient quality and mineral element absorption of brassica rapa.With the increase of nutrient solution concentration,the content of vitamin C in brassica rapa showed a trend of first increasing,then decreasing,and then increasing.Under T_1.5treatment,the content of vitamin C was the highest,5.8%higher than CK treatment.Except T_1.5treatment,the other treatments were significantly lower than CK.With the increase of the concentration of nutrient solution,the content of crude protein increased significantly.The content of crude protein was the highest under T_2.5treatment,which was14.8%higher than CK.In terms of mineral element absorption,with the increase of nutrient solution concentration,the absorption of N by brassica rapa showed a significant upward trend.Except that T_0.5treatment was significantly lower than CK,other treatments were significantly higher than CK.The absorption of K,Ca and Mg showed a trend of first increasing,then decreasing and then increasing,and all reached the maximum value under T_2.5treatment;The absorption of P in brassica rapa was significantly lower than that in CK;The absorption of Fe increased with the increase of nutrient solution concentration,reached the maximum under CK treatment,and then decreased gradually;The absorption of Mn by brassica rapa decreased significantly with the increase of nutrient solution concentration.3.Under different nutrient solution concentrations,T_0.5treatment significantly increased the contents of PRO,SIN,NAP,GBN and 4OH and total glucosinolates,aliphatic glucosinolates of brassica rapa;The content of indole glucoside was the highest under T_2.5treatment.4.Appropriate nitrate concentration treatment was beneficial to the growth of brassica rapa and the accumulation of photosynthetic pigments.High or low concentration of nitrate nitrogen will inhibit growth.The plant height,stem diameter,leaf area,root length and biomass of brassica rapa first increased and then decreased with the increase of nitrate concentration.Compared with CK,the plant height,stem diameter,root length and leaf area of N₁₀treatment increased by 21.1%,12.1%,28.2%and 44.2%,respectively.Chlorophyll content and root activity also increased first and then decreased with the increase of concentration,and both had the maximum value in N₁₀treatment.5.There was no significant difference in vitamin C content and crude fiber content among the treatments under different nitrate nitrogen concentrations.However,with the increase of nitrate concentration,the crude protein content in brassica rapa showed a trend of increasing first and then decreasing.When treated with N₁₀,the crude protein content in brassica rapa was 1.1 times of CK.In terms of mineral accumulation of brassica rapa,with the increase of nitrate nitrogen concentration,the absorption of N,K,Mg,Ca and Fe by brassica rapa increased first and then decreased,but the absorption of N and Mg was the highest under N₁₀treatment,and the absorption of K,Ca and Fe was the highest under CK treatment.The absorption of P by brassica rapa showed a trend of first decreasing,then increasing and then decreasing,and the highest content was 6.02 mg·g^-1under N₁₀treatment.The absorption of Mn decreases with the increase of concentration.6.Ten glucosinolates were detected in brassica rapa under different concentrations of nitrate nitrogen.Among them,N₂treatment significantly increased the content of total glucosinolates,aliphatic glucosinolates and aromatic glucosinolates in brassica rapa.N₁₄treatment significantly increased the content of indole glucosinolates in brassica rapa.To sum up,under the treatment of different nutrient solution concentrations,the growth index,biomass,leaf water content and total chlorophyll of brassica rapa under T_2.5treatment took the first place among all treatments;It also significantly increased the content of indole glucoside,the content of crude protein in nutritional quality and the absorption of mineral elements N,K,Ca and Mg by brassica rapa.Therefore,for the purpose of production,T_2.5treatment was the concentration of nutrient solution suitable for brassica rapa growth and quality improvement,and T_0.5treatment was beneficial to enhance the biological activity of brassica rapa.With the increase of nitrate concentration,the growth of brassica rapa showed a trend of increasing first and then decreasing.Under N₁₀treatment,the growth index,biomass,leaf water content,chlorophyll content and root activity were the highest,and the vitamin C content,crude protein content and indole glucoside content also ranked first among all treatments.N₁₀treatment significantly promoted the growth and quality of brassica rapa.Therefore,for the purpose of production,N₁₀treatment was beneficial to the growth and quality of brassica rapa,and N₂was beneficial to enhance the biological activity of brassica rapa.