| The study was carried out in orchard of Shandong Agricultural University fruit research station from 2014 to 2015.Two-year-old Fuji/Malus robusta biennial plants and Malus Hupehensis Rehd.seedlings were selected as test materials,and the plants were potted in sand fertilized with Hoagland's solution,as the seedlings were cultivated in solution culture,then to study of nickel on absorption,transformation and distribution of 15N-urea on apple and Malus Hupehensis Rehd.seedlings.Effects of different Ni levels on nickle content,glutamine synthetase?GS?activity,superoxide dismutase?SOD?activity of leaves,and other physiological indexs were analysed in the study.Besides,Malus Hupehensis Rehd.seedlings were used under soil culture by pot experiment,to explore the effects of applying nickel into soil on the growth of apple rootstock and its 15N-urea utilization.The main results were followed:1 ? With the increase of nickel levels,the nickel content in apple leaves improved correspondingly.Under low concentration of nickel treatment?Ni0.5,Ni1.0,Ni2.0?,the GS activity and SOD activity in leaves were higher than those of Ni0 treatment,and the treatment with 11.16 ?g·kg-1 nickel in sand?Ni1.0?had the highest effect in the study.However,the GS activity and SOD activity in leaves under high concentration of nickel treatment?Ni10?were significantly lower than those of Ni0.The 15N-urea utilization ratio of Ni0.5,Ni1.0 or Ni2.0 treatment was significantly higher than that of Ni0,and the 15 N use efficiency of Ni1.0 was up to 48.74%,which was 1.71 times as many as that of Ni0,but the 15 N use efficiency of Ni10 reduced by 38.26% compared with Ni0.Nickle also had obvious effect on the 15 N distribution ratios in the apple trees.The 15 N distribution ratio in roots was the highest,followed by leaves and stems in terms of Ni1.0 treatment.However,15 N distribution to leaves was the highest of the other treatments.Overall,our results suggested that appropriate nickel concertration could increase the GS and SOD activities,retard senescence of apple leaves,and improve the absorption and utilization of urea,but high nickel concertration could result in the opposite effect on utilization of urea.2?There was a positive correlation between the total nickel content in seedlings and Ni levels,and the concentration and content in roots were significantly effected by nickel.The biomasses of Ni0.02 and Ni0.04 treatments enhanced by 46.2% and 34.3% compared with Ni0,but it was decreased by 26.1% in Ni0.4.Root activity in Ni0.02 was the highest,while the lowest was Ni0.4.At the 16 th day,chlorophyll content and related enzyme activities in leaves maintained high level in Ni0.02 and Ni0.04,but the lowest were found in Ni0.4.The MDA content in leaves was very low under Ni0.02 and Ni0.04 treatments,while it was high in Ni0.4.The total 15 N absorption of Ni0.02 and Ni0.04 was improved by 82.6% and 86.5% respectively compared with Ni0,and the Ndff value in different organs and the 15 N distribution in leaves increased significantly,meanwhile the 15 N use efficiency was raised by 154.8% and 146.7% respectively.On the contrary,the total 15 N absorption was decreased by 47.7% in Ni0.4,while 15 N use efficiency was significantly decreased by 50.6% compared with Ni0.The results showed that Ni0.02 and Ni0.04 could maintain the activities of enzymes in high levels,promote 15 N use efficiency and seedlings growth,however,it went against the seedlings growth and 15 N use efficiency in Ni0.4.Malus hupehensis Rehd.seedlings were sensitive to nickel,the root activity,GS and NADH-GOGAT activities in leaves improved effectively in the suitable concentration of Ni,meanwhile,the seedlings growth and 15 N utilization were promoted,but high concentration of nickel could have opposite effects.3?Under Ni10 treatment,the leave and root fresh weight,root activity,GS,NADH-GOGAT and SOD activities in leaves were decreased significantly,while the soil nickel content,root total nickel content and malondialdehyde?MDA?content in leaves were increased obviously.Meanwhile,the 15 N distribution in leaves and the 15N-urea use efficiency were significantly lower compared with Ni0.However,the dry weight of different parts were increased,and the scapus was overstriking.Therefore,in this experiment,the Ni10 treatment went against the relative water content of leaves and roots,as well as the 15N-urea absorption and utilization of seedlings were inhibited,but it in favour of the stem thickening growth. |
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