Studies On Nitrogen Absorption, Utilization Of Apple Dwarf Interstock And Its Effect On Leaf Senescence

The study was carried out in orchard of Shandong Agricultural University fruit research station from 2013 to 2014.Two-year-old Fuji 3/M. micromalus Makin, Fuji 3/M7, Fuji3/M26/M. micromalus Makin were used to research the effects of different and scion rootstock combinations on leaf senescence, Rubisco activity, RCA activity and it’s gene expression under different nitrogen levels in sand culture, in order to reveal the relationship between nitrogen and senescence and its mechanism. At the same time, the study was carried out in the orchard of Laishan District of Shandong city in Yantai Province from 2012 to 2014. Five/Six-year-old dwarf apple trees and15 N trace technique were used to research the effects of different nitrogen methods on 15N-Urea absorption, utilization and anti-aging nitrogen management technology, in order to provide a scientific basis for nitrogen management of dwarf orchard.The main results were as follows:1. The effects of different scion rootstock combinations on leaf senescence, Rubisco activity,RCA activity and its gene expression and 15N-urea absorption, utilization under different nitrogen levels in sand culture were explored in the study. The main results were as follows: At Autumn shoot growth arrest stage, the plant leaf chlorophyll content(SPAD) and nitrogen content from high to low were in order of Fuji 3/M. micromalus Makin > Fuji 3/M7 > Fuji 3/M26/M.micromalus Makin under 0N and 25%N treatments. While under 100%N treatment, the plant leaf SPAD and leaf nitrogen content of Fuji 3/M26/M. micromalus Makin were the highest,and then followed Fuji 3/M7, with the indicators of Fuji 3/M.micromalus Makin were the lowest. The leaf SOD and CAT activity of Fuji 3/M.micromalus Makin exceeded Fuji 3/M7 and Fuji 3/M26/M. micromalus Makin under 0N and 25%N treatments, while under 100%N treatment, the leaf SOD and CAT activity were obviously the highest in Fuji 3/M26/M.micromalus Makin, and then in Fuji 3/M7, the minimum was found in Fuji 3/M.micromalus Makin at later stage of the plant growth. Regarding to the leaf MDA content, the results from high to low were in order of Fuji 3/M26/M. micromalus Makin > Fuji 3/M7 > Fuji 3/M.micromalus Makin under 0N and 25%N treatments, while Fuji 3/M26/M. micromalus Makin and Fuji 3/M. micromalus Makin presented the highest and lowest leaf MDA respectively under 100%N treatment. The leaf area, SPAD, nitrogen content of the apple trees with different stock-scion combination increased with the nitrogen application level. The leaf SODand CAT activity increased with the nitrogen application level, while the leaf MDA content decreased with the nitrogen level.The leaf Pn, Rubisco activity and RCA activity of each stock-scion combination apple trees increased first, then decreased under the same nitrogen level, among them Fuji 3/M.micromalus Makin were the largest, then followed in Fuji 3/M26 /M. micromalus Makin, and Fuji 3/M9 /M. micromalus Makin were the lowest under 0N and 25% N treatment., while the leaf Pn, Rubisco activity and RCA activity of Fuji 3/M9 /M. micromalus Makin were the largest, then followed in Fuji 3/M26 /M. micromalus Makin, and Fuji 3/ M. micromalus Makin were the lowest under 100% N treatment.. The leaf Pn, Rubisco activity and RCA activity of each stock-scion combination apple trees increased with the increase of nitrogen concentration under different nitrogen application level. The expression of gene Md RCA-1 and Md RCA-3 have the same trend which increased under nitrogen stress, but the expression of gene Md RCA-2 decreased under nitrogen stress. The expression of gene Md RCA-1 and Md RCA-3 of Fuji 3/M9/M. micromalus Makin were the largest, then followed in Fuji 3/M26 /M. micromalus Makin, and Fuji 3/M. micromalus Makin were the lowest under the same nitrogen level(0N and 25%N),but that of Fuji 3/M. micromalus Makin were the largest, then followed in Fuji 3/M26 /M. micromalus Makin, and Fuji 3/M9/M. micromalus Makin were the lowest under 100% N treatment, while the expression of gene Md RCA-2 of Fuji 3/M. micromalus Makin were the largest, then followed in Fuji 3/M26 /M. micromalus Makin, and Fuji 3/ M9/M. micromalus Makin were the lowest under the same nitrogen level( 0N and 25% N),but that of Fuji 3/M9/M. micromalus Makin were the largest, then followed in Fuji 3/M26/M. micromalus Makin, and Fuji 3/M. micromalus Makin were the lowest under100% N treatment.Significant difference can be seen on the 15 N derived from fertilizer(Ndff%) value of different organ under different nitrogen application levels. Specifically, Fuji 3/M. micromalus Makin was obviously the highest, and then in Fuji 3/M7, while Fuji 3/M. micromalus Makin was the lowest in Ndff% under different nitrogen application levels at fruit maturity period.The nitrogen utilization ratio of apple trees with different stock-scions combination under different nitrogen application levels(0N, 25%N and 100%N respectively) were in order of Fuji 3/M. micromalus Makin(45.60%, 38.97% and 30.80%) > Fuji 3/M7(37.61%, 31.54%and 23.85%) > Fuji3/M26/M. micromalus(33.97%, 27.28% and 20.16%). With the increasing application of nitrogen, the nitrogen utilization ratio of the apple trees increased similarly.2. The effects of different nitrogen application rates on 15N-urea absorption, utilizationand loss in dwarfed apple trees were explored in the study. The results show that there were different values of plant growth,15 N absorption, utilization and loss under different treatments.The plant leaf chlorophyll content(SPAD), total N content and the biomass in N150 treatment were obviously higher than N50 and N250 treatments, and root-shoot ratio significantly increased. Significant differences can be seen on the Ndff% value of different organs under different nitrogen application rates. Ndff% of the fruits(flowers), leaves, annual shoots, and perennial branches at the determination period were N50 >N150>N250 treatment, but Ndff%of the roots at full-bloom and new shoot growing stage were N50 >N150>N250 treatments,and at flower bud differentiation, fruit rapid-swelling and fruit maturity Stage were N150 >N50>N250 treatments. At fruit maturity Stage, Significant differences can be seen on the N residuals in soil under different nitrogen application rates, which was N150(2.10g)<N50(2.50g) <N250(2.81g) treatments, and the majority of residual N is concentrated in0-60 cm layer, which indicated fertilizer nitrogen losses in deep soil layers were small. At fruit maturity stage plant 15 N nitrogen ratio of N150 treatment was 23.62%, which was obviously higher than N50(16.33%) and N250(14.44%) treatments, and15 N loss rate was 56.37%,which was obviously lower than N50(60.55%) and N250(66.05%) treatments.3. The effects of different depths of fertilizer application treatments on15N-urea absorption, utilization and loss in dwarf apple trees were explored in the study. The results showed that the plant leaf area, soil and plant analyzer develotrnent(SPAD value) and total N of apple leaves in 20 cm treatment were obviously higher than 0 cm and 40 cm treatments.The Ndff% in different organs of apple plant under different depths of fertilizer application treatments were significantly different, and the Ndff% was the highest in roots at the full-bloom stage, and then in perennial branches. During the shoot rapid-growing and flower bud differentiation stage, the Ndff% of new organs were higher than that of the storage organs,and the Ndff% of different organs were in high level at fruit rapid-expanding stage, and at fruit maturity stage the Ndff% of fruit was the highest. The distribution ratio of15 N at fruit maturity stage was significantly different under different depths of fertilizer application treatments, and that of the vegetative and reproductive organs of 20 cm treatment were obviously higher than 0 cm and 40 cm treatments, but that of the storage organs of 20 cm treatment was lower than 0 cm and 40 cm treatments. At fruit maturity stage apple plant15 N nitrogen rate of 20 cm treatment was 23.96%, which was obviously higher than 0 cm(14.07%)and 40 cm(7.60%) treatments, and15 N loss rate was 54.02%, which was obviously lower than0 cm(67.75%) and 40 cm(63.48%) treatments. With increase of fertilizer depths, the Nresidue in soil sharply increased under different depths of fertilizer application treatments.4. The effects of different N fertilization stages on15N-urea absorption, distribution and utilization in the dwarf apple trees were explored in the study. The results show that the Ndff% in different organs are significantly affected by the application date. The highest Ndff% was in roots at the full-bloom stage when the urea was applied at the bud stage,followed were in the perennial branches. From the spring shoot slowly growing stage to fruit rapidly swelling stage, the Ndff% values of new organs are higher than those of to the storage organs. At the fruit premature stage, the Ndff values of different organs are in high level, and at fruit maturity stage the Ndff% value of fruits is the highest. When the fertilization was applied at the spring shoot slowly growing stage, the Ndff% in roots of the autumn shoot growing stage is the highest, the Ndff% values of new organs are at a high level at the fruit maturity stage, and the Ndff% of fruits is the highest. The Ndff% values of the storage organs(roots and perennial branches) are at a high level in each period under the autumn shoot growing stage fertilization treatment. Therefore, along with the changing of the phenological period,the Ndff% values of new organs(annual branches, leaves and fruits) aboveground increase gradually, and reach the peak till the fruit maturity stage, but the 15 N absorption ability of fruits is weakened in comparison. The 15 N distribution ratios of each organ at the fruit maturity stage are significantly different among different treatments. The 15 N distribution ratio in the vegetative organs is the highest when urea was applied at the bud stage, and that was in reproductive organs when the urea was applied at the spring shoot growing slowly stage, and that was in the storage organs when applied at the autumn shoot growing stage.There are significant differences in the total N contents of plant, the Ndff% and their utilization rates with the three application stages at fruit maturity stage. The highest values(86.34 g, 1.38 g and 30.07%) were measured in the saplings applied fertilizer at the spring shoot growing slowly stage, then was at the autumn shoot growing stage(75.64 g, 1.25 g and27.22%) and the lowest(72.82 g, 1.09 g and 23.63%) was at bud stage fertilization.5. The effects of fruit load on absorption, distribution and utilization of 15N-Urea applied in dwarf apple trees were explored in the study. The main results were as follows: the leaf area,chlorophyll content(SPAD) and the single fruit weight significantly increased compared with control(non-thinning), with the single fruit weight of 2/3 fruit load treatment and 1/3 fruit load treatment treatment increasing 19.02% and 37.38% respectively, and root-shoot ratio significantly increased, however the average yield per plant significantly decreased.Significant differences can be found on the Ndff% value of different organs, with the fruit Ndff% showing the highest and then the perennial branches, leaves and roots of the threetreatments. The Ndff% of fruit decreased with fruit thinning increased, and that of perennial branches, leaves and roots increased on the contrary. Fruit15 N distribution ratio of the three treatments(control, 2/3 fruit load and 1/3 fruit load treatment treatment) were 35.32%,28.35% and 18.18% respectively, however, that of the biennial branch, leaves and roots increased with the increasing fruit thinning. Plant 15 N utilization of the three treatments(control, 2/3 fruit load and 1/3 fruit load treatment treatment) were 19.59%, 22.01% and28.35% respectively, indicating that the 15 N utilization ratio increased significantly with the increasing fruit thinning.6. The effects of autumn foliar application of high concentration urea on growth in the following spring and fruit quality in dwarfed apple trees were explored in the study. The results show that the utilization efficiency of nitrogen was observed 88.88%, 83.44% and73.98% respectively by different autumn foliar application of15N-urea(1.50%N, 3.00%N and4.50%N) in the dormant season due to the high capacity of nitrogen absorption. Significant difference can be seen on Ndff% value in different organs in the following year, and the highest value was seen in 4.50% N treatment, then followed in the 3.00% N treatment, and the lowest was presented in 1.50% N treatment. At the full-bloom stage, the Ndff% value of perennial branch was the highest, and then followed leaf, flower and root successively,indicating that the nitrogen absorbed by leaf was primarily stored in perennial branches. At spring shoot growth stage, the Ndff% of leaf was the highest, followed by annual branch,perennial branches and root, and the lowest value was observed in trunk. The plant leaf area,SPAD and the total N content of leaves were found significant difference at fruit maturity stage, specifically, the highest value was found in 4.50%N treatment, and then followed3.00%N and1.50%N treatment, while the lowest was observed in control, which was consistent with the presentation of the physiological indicators, such as mean fruit weight,yield per plant, soluble solid, fruit firmness, soluble sugar content and sugar-acid ratio. The results showed that the fruit quality was improved by foliar application of nitrogen in the dormant season, but the effect varied among different nitrogen concentrations.7. The effects of topdressing nitrogen application at fruit rapid-swelling stage on absorption and utilization of 15N-Urea applied in dwarf apple trees were explored in the study.The main results were as follows: significant differences can be seen on chlorophyll content(SPAD), total N content of leaves, average fruit weight and average yield per plant under different topdressing nitrogen treatments, and five-time topdressing application was the highest, and then in three-time topdressing application, and the last was the five-time topdressing application. The total N content of plant, 15 N absorbed from 15N-urea and15N-urea utilization rate of five-time topdressing treatment were the highest, which were85.95 g, 1.19 g and 25.86% respectively, and then in three-time topdressing application, which were 81.34 g, 0.98 g and 21.40% respectively, and one-time topdressing application was the least. which were 75.46 g,0.73 g and 15.90% respectively, and there are significant differences between the three treatments. At fruit maturity stage the Ndff% of fruit was the highest, and then in biennial branch, leaf, root, branch of perennial, the Ndff% of trunk was the least.Significant differences can be seen on the Ndff% of plant organs under different topdressing nitrogen treatments, and five-time topdressing application was the highest, and then in three-time topdressing application, and the last was the five-time topdressing application.