| Hydroponics is a modern agricultural technology,which has the advantages of high yield per unit area,high product standardization,avoiding continuous cropping obstacles and shortening the growth period,which has been widely used in facility production.Spinach is an important green leaf vegetable in the world.However,there are few reports and researches on spinach hydroponics technology.In this study,the research on spinach hydroponics technology is carried out from the aspects of nutrient solution screening and improvement,pre-germination treatment method,addition of growth regulator,variety screening and hydroponics adaptability mechanism,etc..The aim of this study is to lay a foundation for improving spinach hydroponics technology and cultivating new spinach varieties special for hydroponics.The main research results are as follows:1.In order to select the nutrient solution formula suitable for hydroponic growth and spinach varieties,this experiment compared the effects of different nutrient solution formulas on spinach growth and quality indexes.The results showed that among the 6 nutrient solutions with the same nitrogen supply level(8 mmol·L-1)（0.76 times modified Hoagland,0.46 times Japanese garden trial,1.23 times Japanese Yamazaki,0.38 times horticultural equilibrium,south China agricultural leafy vegetable A,south China agricultural leafy vegetable B nutrient solution）,the fresh weight,plant height,leaf width and root length of spinach treated by Japanese Yamazaki formula were the highest.The comprehensive performance of formula A of South China Agricultural University is second only to Yamazaki of Japan.The fresh weight,leaf number,leaf width and root length（except Yamazaki,Japan）of spinach treated with balanced formula of Yamazaki,Japan and horticulture were higher than those of other formulas under the condition of shallow water culture in greenhouse.The soluble protein and chlorophyll content of spinach treated with Yamazaki formula in Japan were lower,but nitrate nitrogen content was also the lowest.The contents of nitrate nitrogen,chlorophyll and soluble protein in spinach（except South China Agricultural University A）were the highest under the treatments of South China Agricultural University A and horticultural balanced formula.The contents of vitamin C,soluble sugar,soluble sugar,soluble sugar and soluble oxalic acid were not significantly affected by different nutrient solution formulations.2.Based on the original Yamazaki formula,different concentrations of nitrogen,magnesium and humic acid（HA）were applied to increase the concentration of magnesium to 4 times(2.464 mmol·L-1)to significantly increase the fresh weight of spinach,which was 2.69 times as much as that of the control.However,when nitrogen increased to 1.5 times(12 mmol·L-1)and magnesium increased to 4 times(2.464 mmol·L-1),the nitrate nitrogen content of spinach was the lowest,and the fresh weight of spinach was significantly higher than that of the control,which was 2.00 times that of the control,indicating that the appropriate nitrogen-magnesium ratio could increase the yield of hydroponic spinach to a greater extent.Adding humic acid with different concentrations（0-0.232%）to hydroponic solution inhibited spinach growth.3.In order to select suitable growth regulators for spinach hydroponics,the effects of cytokinin,humic acid and alga spray on the growth and quality of spinach hydroponics were compared.The results showed that spraying humic acid significantly increased the fresh weight of hydroponic spinach ‘Hubo 6 ‘and ‘WD’,which were 2.31 times and 1.08 times higher than those of clean water control group respectively.Application of cytokinin and alga spray significantly reduced the fresh weight of hydroponic spinach ‘Hubo 2’ and ‘WD’.Cytokinin significantly increased the plant height of ‘Hubo 2’ and ‘Hubo 6’,while cytokinin decreased the plant width of ‘WD’,while humic acid significantly increased the plant width of ‘Hubo 6’.In addition to the increase of nitrate content in spinach,the three growth regulators had no significant effect on the content of chlorophyll,soluble protein,free amino acid,soluble sugar and VC.4.Proper pretreatment of spinach seeds before germination can improve spinach germination ability and promote hydroponic growth performance.Compared with the control group（T1,soaking seeds in distilled water for 15 min）,the electrostatic field treatment of 50 k V·5 cm-1× 20 s significantly improved the germination potential,germination rate and germination index of spinach seeds,which were 3.11,2.00 and 2.21 times of the control group respectively,followed by the chemical treatment of 100 mg·L-1 PEG8000 soaking for 24 h.Both electrostatic field treatments and chemical treatments can promote the growth of spinach hydroponics seedlings.The width,plant height,root length and fresh weight of spinach hydroponics leaves treated with chemical treatment T5(soaking with 100 mg·L-1 PEG 8000 for 24 h)are significantly higher than those of control group（soaking with distilled water for 15 min）,were are 1.50 times,1.43 times,2.24 times and 2.66 times of T1 respectively.Under chemical treatment T7（soaking in 1% boric acid for 24 h）,the leaf width,root length and fresh weight of overground part of hydroponic spinach were significantly higher than those of control group,and were 1.45 times,2.34 times and 2.21 times of T1 respectively.The leaf width,leaf length,root length and fresh weight of hydroponic spinach shoots treated by electrostatic field T14（50 k V·5 cm-1× 20 s）were significantly higher than those of control group,which 1.58 times,1.18 times,1.77 times and 1.99 times greater than those of T1 respectively.5.The growth performance of different spinach materials（‘WD’,‘Aolv’,‘Hubo 2’ and ‘Japlan large-leaf’）were different under hydroponic conditions.Under hydroponics,the shoot fresh weight of ‘WD’ and ‘Aolv’ were 2.65 and 2.68 times greater than those cultured in substrate,respectively.And the number of leaves,width of leaves,length of leaves and plant height of ‘WD’ and ‘Aolv’ were also higher than those cultured in substrate.Whereas,the shoot fresh weight of ‘Japan large-leaf’ grown in substrate culture was 1.2 times of that under hydroponics,which may not suitable for hydroponic cultivation.In addition to the fresh weight,the number,width,length and height of spinach leaves in ‘WD’ and ‘AOLv’ hydroponic culture were higher than those in substrate culture.The better growth performance of ‘WD’ and ‘Aolv’ under hydroponics may be related to their relative longer main root length and lateral root number,higher nitrate reductase activity,root activity and the more developed secondary xylem in rhizome structure when compared with those under substrate cultivation.The developed parenchyma cell structure on the outer side of the stem periderm of ‘Japlan large-leaf’ were disappeared under hydroponics,and the number of adventitious roots,nitrate reductase activity,root activity of ‘Japlan large-leaf’ were also decresed,which may be related to its poor adaptability to hydroponics. |
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