Effects Of Ethylene On The Absorption,Distribution And Utilization Of Nitrogen In Apple Dwarfing Rootstocks M9T337 And M26

The experiment was carried out in Shandong Agricultural University,Tai'an City,Shandong Province from 2017 to 2018.The effects of ethylene on the absorption,utilization and distribution characteristics of nitrate nitrogen and ammonium nitrogen were studied using apple rootstock M9T337 and M26 seedlings as test materials.Besides,M26 tissue culture seedlings were used as experimental materials to study the effects of ethylene inhibitor Ag⁺on nitrogen uptake,utilization and distribution.The main test results are as follows:1.Foliar application of ethephon increased the root activity of M9T337 seedlings.In the 20days after treatment,the root activity of the two treatments was obviously higher than that of the control,and the 400?l/L ethephon treatment increased more obviously.The activities of nitrate reductase?NR?and glutamine synthetase?GS?in the roots and leaves of different treatments first increased and then decreased after treatment,and reached the peak at 8th day.The activity of two enzymes in the root of ethephon treated seedlings was higher than that of the control,but the activities of the two enzymes in the leaves were higher than the control within 12 days after treatment,and lower than the control at 16-20 days.Ethephon treatment increases the root-shoot ratio while increasing the biomass of the seedlings.The utilization rates of the two treatments of 200?l/L and 400?l/L were 1.37 times and 2.61 times,respectively;the root distribution ratios of 200?l/L and 400?l/L were 33.32%and 67.40%higher than the control.2.Foliar application of ethephon on leaf surface of M26 seedlings could increase the root length,root surface area,root tip number,root volume and other root morphological indexes and root vigor of seedlings in nitrate nitrogen and ammonium nitrogen.After that,the root morphology index and root activity were reduced,and the effect of treated with Ag⁺was more significant.The root length,root surface area,root tip number and total root volume of seedlings in nitrate with Ag⁺were 32.14%,11.90%,19.54%and 54.76%lower than CK1,respectively.The root length,root surface area,number of root tips and total root volume of seedlings in ammonium nitrogen with Ag⁺were 34.34%,38.17%,42.97%and 28.11%lower than CK2,respectively.At the same time,ethephon could increase the nitrogen partitioning rate of seedling roots.The nitrogen partitioning rate of the roots of ethephon-treated seedlings in ammonium nitrogen was 64.71%higher than that of CK2,while the ethylene inhibitor Ag⁺reduced the nitrogen partitioning rate in seedling roots.Compared with the control,ethephon could increase the antioxidant enzyme activity and NR activity in roots and leaves,and the total nitrogen and ¹⁵N absorption increased significantly.The nitrogen utilization rate of the seedlings treated with ethephon in nitrate nitrogen and ammonium nitrogen was 30.49%and31.13%higher than that of control,respectively.After treatment with ethylene inhibitor,the total nitrogen content,total ¹⁵N absorption and nitrogen utilization rate were decreased in the seedlings,and the effect of root application of Ag⁺was more significant.3.Root surface area,root length and total volume of M26 tissue culture seedlings after Ag⁺treatment showed reduction.The root surface area decreased the most,and the 2.5 mmol/L and 5 mmol/L Ag⁺treated seedlings were 24.13%and 40.29%lower than that of the control,respectively.At the same time,Ag⁺treatment reduced the ¹⁵N distribution rate in the roots.Ag⁺treatment also reduced the NR activity and antioxidant enzyme activity of tissue culture seedlings,inhibited the growth of tissue culture seedlings,and the nitrogen utilization rates of2.5 mmol/L and 5 mmol/L Ag⁺were 40.60%and 56.27%lower than that of the control,respectively.