The Effects Of Exogenous Calcium On Nitrogen Absorption And Utilization Of Apple

Apple has a long history of planting in China,and it is one of the fruit trees with the largest cultivated area in China.Insufficient nitrogen use efficiency often occurs in apple orchard production in China,and how to improve nitrogen use efficiency has become a key problem for the sustainable development of modern fruit industry.Calcitonin affects nitrogen metabolism in Gramineae plants,but it has not been reported in apple.In 2019,Malus hupehensis Rehd seedlings were treated with 0.2N?0.2 mmol·L^-11 NO₃^-?and 3N(3 mmol·L^-1NO₃^-).On this basis,1 mmol·L^-11 EGTA?calcium chelating agent?was set up,and different CaCl₂ concentration gradients were 0,0.1,1 and 3 mmol·L^-1.Respectively,to study their effects on physiological growth,nitrogen absorption and utilization of Malus hupehensis Rehd seedlings..In April 2019,the normally managed two-year-old'Fuji/Malus hupehensis Rehd'as the test material.On April 28 th,30 g/strain KNO3;on May 6 th,the four treatments of 0?CK?,3,10 and 30 g/strain CaCl₂ were applied and on August 6th,various indexes were detected.The effects of different amounts of calcium fertilizer on plant growth,root development and nitrogen metabolism of'Fuji/Malus hupehensis Rehd'were studied.The main results are as follows:?1?Under different nitrogen levels,calcium application promoted the above-ground growth of Malus hupehensis Rehd seedlings,increased leaf area,leaf dry weight,fresh weight and chlorophyll,and improved leaf quality.At the level of 0.2N,the concentration of calcium was 0.1 mmol·L^-11 and at the level of 3 N,the combination of calcium concentration of 1mmol·L^-11 had the best effect on the aboveground growth of Malus hupehensis Rehd seedlings.At the same calcium level,the effect of nitrogen on aboveground index was 3 N>0.2 N.?2?External application of calcitonin promoted the development of under-ground part of Malus hupehensis Rehd seedlings at 0.2 N and 3 N levels,increased underground biomass,root index,root activity,and promoted root development.Under both nitrogen levels,the root system developed best under 0.1 mM Ca²⁺treatment.At 0.2 N level,the underground biomass increased by 148.3%compared with the control,and increased by 55.2%compared with the control.At the same calcium level,the effect of nitrogen on underground index was 0.2 N>3N.?3?Under different nitrogen levels,the calcium content of Malus hupehensis Rehd seedlings increased with the increase of calcium application.At 0.2 N and 3 N levels,calcium application promoted nitrogen metabolism of Pingyi sweet tea seedlings.Compared with the control,calcitonin increased the absorption of NO₃^-,decreased the accumulation of NH₄⁺,increased the activities of NR and GS,and increased the accumulation of total N.At 0.2N level,0.1 mM Ca²⁺treatment and 3 N level,1 mM Ca²⁺treatment had the best effect on plant nitrogen metabolism.The overall performance is as follows:low nitrogen and low calcium,high nitrogen and high calcium.?4?Similar to the results of seedlings,the application of calcium fertilizer in-creased plant chlorophyll,leaf area,plant height and stem diameter.Compared with no calcium fertilizer,each index of 3 g/plant CaCl₂ treatment increased the most,which increased by 17.7%,2.3%,11.1%and 9.8%,respectively.Compared with the control,the root activity of'Fuji/Malus hupehensis Rehd'was increased by proper applying calcium fertilizer.The net photosynthetic rate,transpiration rate and stomatal conductance of'Fuji/Malus hupehensis Rehd'were increased by external application of calcium fertilizer,and the treatment of 3 g/plant CaCl₂ was the best.?5?The external application of calcium promoted the nitrogen metabolism of'Fuji/Malus hupehensis Rehd'.The contents of nitrate nitrogen,ammonium nitrogen,total nitrogen,NR and GS activities in roots and leaves were increased.The effect of 3 g/plant CaCl₂ treatment was the best.The calcium accumulation in roots increased with the increase of total calcium application,which was the highest at 30 g/plant CaCl₂ treatment,and the leaf calcium content was the highest at 3 g/plant CaCl₂ treatment.The above results confirmed the possibility of the application of seedling test results in the field,and the application of a small amount of calcium in Shandong area was beneficial to improve the nitrogen use efficiency of apples.