Effects Of Phosphorus Application On Root Morphology,Physiology And Soil Phosphorus Characteristics Of Platycodon Grandiflorum

This experiment was carried out with the 2-year-old P.grandiflorum as experimental material in the medicinal plant cultivation base of Shandong Agricultural University.The experiment sets two phosphorus application rates and two phosphorus application depths:no diammonium phosphate application?no phosphate,CK?,low level phosphorus application(40 kg_·hm^-2,15 cm,middle),low phosphorus application(40 kg_·hm^-2,25 cm,deep),high level phosphorus application(60 kg·hm^-2,15 cm,middle),high level phosphorus application(60 kg·hm^-2,25 cm,deep),there are totally 5 treatments.The effects of phosphorus application on phys-iological characteristics,phosphorus absorption,soil PH,soil phosphorus content and soil enzyme activity of P.grandiflorum root were studied,in order to reveal the change rules of different phosphorus application rates and phosphorus application methods on the root morphology,physiology and soil characteristics of P.grandiflorum,which provides a theoretical basis to guide the application of phosphate fertilizer in the production of P.grandifl-orum.The main findings are as follows:1.Phosphorus application increased the main root length and main root thickness of P.grandiflorum,reducing the number of roots.With the increase of phosphorus application rat-e,the root length of P.grandiflorum reduced,and the application of phosphorus fertilizer in t-he middle was more conducive to the thickening of the main root of P.grandiflorum than in the deep.From the fruiting period to the harvesting period,the main roots of the low-phosphorus in the middle were significantly higher than other treatments.In the early growth stage of platycodon grandiflorum,the main root length of P.grandiflorum was the longest in the low-phosphorus at medium level;During the harvesting age,the number of lateral roots of platycodon grandiflorum in low phosphorus of deep level was the least2.Low phosphorus application at intermediate level significantly increased the root activity of P.grandiflorum.During the harvesting period,the CAT activity of roots treated with phosphorus was significantly higher than that of the non-phosphorus-treated control,and the highest CAT activity was observed in high-phosphorus of middle level.The POD activity of roots with high phosphorus application of deep level was the highest.Phosphorus application reduced SOD activity of platycodon roots.In the phosphorus treatment,the SOD activeity of platycodon root in the low-phosphorus of intermediate level was higher than that of other phosphorus treatment.Phosphorus application reduced the MDA content of platycodon roots.3.During the vigorous growth and harvesting period,phosphorus application reduces the acid content of P.grandiflorum,which was conducive to maintaining the vigorous growth of Platycodon root.In the fruiting and harvesting period,the zeatin content of platycodon in the low-phosphorus of middle level was the highest,indicating that the low-phosphorus application in the middle was more conducive to the biosynthesis of platycodon zeatin.During the harvesting period,the content of auxin in the high-phosphorus at intermediate level was lower than that in the low-phosphorus,and the content of gibberellin in the high-phosphorus of level was higher than other treatments.4.Phosphorus application significantly increased the phosphorus content in the upper and lower parts of P.grandiflorum.During the harvesting period,the phosphorus content in the upper part of the low-phosphorus of middle level was significantly higher than that in the low-phosphorus of deep level,and the phosphorus content in the upper part of the high-phosphorus of middle level was the highest;The phosphorus content in the lower part of the high phosphorus of deep level was higher than that in the low phosphorus.Low phosphorus of middle level was highest.Regardless of low phosphorus or high phosphorus,the ratio of phosphorus content in the upper part and the lower part of the platycodon in the phosphate fertilizer was higher than that in the deep application,and the highest ratio was found in the low phosphorus in the middle.Phosphorus harvesting index and phosphorus utilization efficiency in low phosphorus of intermediate level were significantly higher than other treatments.5.Regardless of phosphorus application in middle or deep level,phosphatase activity of high phosphorus treatment soil was always higher than that of control and low phosphorus treatment.During the vigorous growth period,flowering stage and fruiting stage of P.grandiflorum,the alkaline phosphatase activity about soil in low-phosphorus deep application was higher than other treatments.Phosphorus application reduced soil acid phosphatase activety and urease activity,increasing soil catalase activity,and had no significant effect on soil sucrase activity.In the early stage of P.grandiflorum,the activity of soil catalase in low phosphor-us of middle level was higher than that in low phosphorus of deep level,and the late growth stage of platycodon was lower than that in low phosphorus of deep level.6.Phosphorus application increased the content of available phosphorus and inorganic phosphorus in the soil.The content of available phosphorus and Ca₂-P in soil with low phosphorus in the middle was the highest.Regardless of low phosphorus or high phosphorus,the content of Ca₂-P I in the soil under the phosphorus treatment of middle level was higher than that in the deep level,and the content of Ca₂-P in the low phosphorus treatment was higher than that in the high phosphorus treatment.During the harvesting period,regardless of low phosphorus or high phosphorus,the content of Ca₈-P in the soil treated with middle level phosphate fertilizer was higher than that in the deep application of phosphate fertilizer,and the content of Ca₈-P in soil with high phosphorus of middle level was the highest.In the fruiting and harvesting periods,the Al-P content in low phosphorus at intermediate level was significantly higher than in other treatments.During the harvesting period,the O-P content in low phosphorus in the middle was higher than other treatments.Conclusion:Low phosphorus application in the middle level significantly increased the main root length and root thickness of P.grandiflorum,and low phosphorus application in the deep level significantly reduced the number of lateral roots of P.grandiflorum.The low phosphorus applicationat intermediate significantly increased the root activity,SOD activity and zeatin content of the P.grandiflorum,and reduced the malondialdehyde content of the platycodon root.The phosphorus content ratio,phosphorus harvest index and phosphorus utilization efficiency of the above-ground and lower parts of platycodon in the low-phosphorus of deep level were significantly higher than other treatments.Phosphorus application reduced soil acid phosphatase activity and urease activity and increased soil catalase activity.The content of available phosphorus and Ca₂-P in soil with low phosphorus in the middle was the highest.Low phosphorus application of middle level significantly increased the total saponins and soluble sugar content of P.grandiflorum.Therefore,under the conditions of this test,the effect of low phosphorus in the middle is best.