外源钙对平邑甜茶幼苗氮素吸收及利用的影响

Effects of exogenous calcium on nitrogen absorption and utilization of Malus hupehensis Rehd.seedlings

【目的】探究钙素施用量对平邑甜茶氮素吸收和利用的影响以及最适宜施钙量。【方法】以正常浓度氮(3.0 mmol·L^-1 NO3^-)处理当年生平邑甜茶幼苗,在此基础上设0(CK)、0.1、1.0、3.0 mmol·L^-1 Ca^2+4种钙浓度梯度,以根部灌施的方式施入。研究钙素施用量对平邑甜茶幼苗生物量、氮相关表观指标和氮同化以及氮积累的影响。【结果】与对照相比外施钙素增加了平邑甜茶幼苗地上部生物量、叶绿素含量、总叶面积以及株高,并在1.0 mmol·L^-1 Ca^2+处理时达到最高水平。同时外施钙素提高了平邑甜茶幼苗的根系指标和根系活力,并在0.1 mmol·L^-1 Ca^2+处理时达到最高水平。外施钙素促进了植株对硝态氮的吸收;降低了植物体内氨离子的含量;提高了氮同化通路中关键酶硝酸还原酶和谷氨酰胺合成酶的活性并促进了氮在植物体内的积累,在1.0 mmol·L^-1 Ca^2+处理下达到最高水平。此外发现不同浓度钙处理导致了植株体内多种元素含量发生改变。【结论】外源钙促进了幼苗氮素的吸收以及利用,正常氮素处理下1.0 mmol·L^-1 Ca^2+可能是平邑甜茶幼苗氮素吸收以及利用的最佳钙浓度。

【Objective】This study was to examine the effect of calcium application on nitrogen absorption and utilization in Malus hupehensis Rehd.and to screen the optimum amount of calcium for application.Calcium and nitrogen are both macronutrients needed by fruit trees.There are many studies on the effect of a single element on the growth of fruit trees,but there are few studies on the interactions of calcium and nitrogen.This study aimed to provide some data for improving the nitrogen use efficiency in apple.【Methods】The seedlings of M.hupehensis Rehd.were applied with 3 mmol·L^-1 NO3^-.On this basis,there were four calcium treatments:0(CK),0.1,1 and 3 mmol·L^-1 Ca^2+.The calcium solutions applied were prepared with analytical pure CaCl2 and adjusted to pH 6.0.Nitrogen and calcium were applied by soil drenching.Twenty-four seedlings with even growth were selected for each treatment,and the effect of calcium on the biomass of different parts of the seedlings was analyzed by drying and weighing the samples.The difference in leaf area among different treatments was analyzed by image J software.The plant height was measured with a ruler and the stem diameter with an electronic Vernier caliper.A root morphology scanner(Epson V 700)was used to collect the root images,which were analyzed with software WinRHIZO and data of total root length,total root area and root tip number in different treatments were obtained.The content of nitrate nitrogen was determined with salicylic acid method.The activity of nitrate reductase was determined by sulfonamide colorimetry,and the changes in nitrate reductase activity were compared between calcium treatment and the control.Glutamine synthetase activity was determined by glutamine synthetase(GS)kit purchased from Suzhou Keming Technology Co.,Ltd..After the underground and aboveground parts of the seedlings were dried at 80℃,they were digested using H2SO4-H2O2 method,and the contents of total nitrogen,total calcium and phosphorus,potassium,iron,magnesium,zinc and molybdenum were determined by automatic Kjeldahl nitrogen meter,atomic absorption spectrophotometer or Icp-Ms.【Results】The aboveground indexes of M.hupehensis Rehd.seedlings was the highest level in the treatment with 1 mmol·L^-1 Ca^2+.The fresh weight and dry weight of the seedlings increased by 31.5%and 33.5%,respectively,and the seedling height increased by 129.3%compared with the control.The total leaf area of the seedlings increased by 49.2%compared with the control.In the treatment with 3 mmol·L^-1 Ca^2+,the stem diameter was the highest,which was 22.8%higher than that of the control.At the same time,calcium increased root length,root surface area,root tip number and root activity,which were highest level in the treatment with 0.1 mmol·L^-1 Ca^2+,where these indexes increased by 24.1%,26.6%,17.3%and 129.9%respectively compared with the control.The application of calcium promoted the absorption of nitrate nitrogen in different parts and reduced the content of ammonia ion in the plant.Calcium content in the plant increased with the increase of the calcium concentration applied.The activities of nitrate reductase(NR)and glutamine synthetase(GS),the key enzymes of nitrogen assimilation,increased with the increase in calcium concentration.Ca^2+treatments significantly affected the nitrogen assimilation in M.hupehensis Rehd seedlings,and the nitrogen assimilation amount in the treatment with 1 mmol·L^-1 Ca^2+was the highest under normal nitrogen level.In addition,we found that different concentrations of calcium led to changes in the contents of phosphorus,potassium,iron,magnesium,zinc and molybdenum in the plant.With the increase in calcium concentration,the aboveground phosphorus content decreased gradually,and phosphorus content in roots increased at first and then decreased,and was the highest at 1 mmol·L^-1,while the contents of potassium,iron,magnesium,zinc and molybdenum increased at low calcium concentrations,but decreased at higher concentrations.Calcium application not only affected the absorption of nitrogen,but also influenced the absorption of the other mineral elements.It is suggested that calcium might play an important regulatory role in the process of nitrogen absorption and assimilation.【Conclusion】Exogenous calcium promotes nitrogen absorption and utilization in M.hupehensis seedlings.Under normal nitrogen treatment,1 mmol·L^-1 Ca^2+may be the best calcium concentration for nitrogen absorption and utilization.