MdBT2 regulates nitrogen-mediated cuticular wax biosynthesis via a MdMYB106-MdCER2L1 signalling pathway in apple.

Cuticular waxes play important roles in plant development and the interaction between plants and their environment. Researches on wax biosynthetic pathways have been reported in several plant species. Also, wax formation is closely related to environmental condition. However, the regulatory mechanism between wax and environmental factors, especially essential mineral elements, is less studied. Here we found that nitrogen (N) played a negative role in the regulation of wax synthesis in apple. We therefore analysed wax content, composition and crystals in BTB-TAZ domain protein 2 (MdBT2) overexpressing and antisense transgenic apple seedlings and found that MdBT2 could downregulate wax biosynthesis. Furthermore, R2R3-MYB transcription factor 16-like protein (MdMYB106) interacted with MdBT2, and MdBT2 mediated its ubiquitination and degradation through the 26S proteasome pathway. Finally, HXXXD-type acyl-transferase ECERIFERUM 2-like1 (MdCER2L1) was confirmed as a downstream target gene of MdMYB106. Our findings reveal an N-mediated apple wax biosynthesis pathway and lay a foundation for further study of the environmental factors associated with wax regulatory networks in apple.

[Effects of large-grained activated humic acid fertilizer on soil aggregates and organic carbon in apple orchard soil]. / å¤§é¢—ç²’æ´»åŒ–è æ¤é ¸è‚¥å¯¹è‹¹æžœåœŸå£¤å›¢èšä½“å’Œæœ‰æœºç¢³çš„å½±å“.

The new large-grained activated humic acid fertilizer (LAF) can significantly reduce the amount of chemical fertilizer application and stable fruit yield. Understanding its impacts on soil aggregates and organic carbon is an important basis for revealing its role in driving soil structure of apple orchard. There were four LAF treatments: LAF1 (full fertilization, fertilization period and mass ratio (the same below), germination stage: fruit expansion stage: maturity stage=3:4:3), LAF2 (full fertilization, germination stage: fruit expansion stage: maturity stage=2:3:5), LAF3 (fertilizer application reduction by 1/4, germination stage: fruit expansion stage: maturity stage=2:3:5), LAF4 (fertilizer application reduction by 1/3, germination stage: fruit expansion stage: maturity stage=2:3:5); with no fertilization as control (CK). In a four-year pot experiment, we examined the composition, stabi-lity and organic carbon content of soil aggregates under different fertilization treatments. The results showed that: 1) compared with CK, each treatment of LAF increased the content of >2 mm and 2-0.25 mm aggregate by 53.4%-77.5% and 12.3%-17.0%, respectively. The application of LAF significantly increased the content of soil water stable aggregates, and such effects were positively related with application amount. The content of soil water stable aggregate was the highest in the LAF1 treatment. 2) There was no significant difference in aggregate content of each particle size among LAF treatments, with the proportion of aggregate content of 2-0.25 mm particle size being the highest. 3) Compared with CK, all LAF treatments significantly increased the average weight diameter (MWD) and geometric mean diameter (GMD), and reduced the fractal dimension (D). LAF1 treatment had the highest MWD and GMD values, and had the strongest effect on the stability of soil aggregates. 4) Except for LAF4 treatment, the content of soil organic carbon in other LAF treatments was significantly higher than that in CK, and the content of soil organic carbon in LAF2 treatment was the highest. All LAF treatments increased the organic carbon content of soil aggregates with each particle size. LAF1, LAF2, and LAF3 treatments significantly increased the organic carbon of aggregates with particle size >2 mm. Particle size >2 mm had the highest contribution to the total organic carbon. The contribution rate of water stable large aggregate organic carbon to total organic carbon of LAF treatment was significantly higher than that of CK, which was all higher than 66.0%, and that of LAF1 treatment was the highest. In conclusion, the application of LAF enhanced the formation and stability of water stable aggregates and increased organic carbon content of aggregates in apple orchard soil, with the best performance of the full application. The application of LAF could be used as an effective measure to improve soil structure and fertility in apple orchard.

[Effects of Na2WO4 on 15N absorption and utilization,13C accumulation of apple seedling, and fruit quality]. / é’¨é ¸é’ å¯¹è‹¹æžœå¹¼è‹—15N吸收利用、13C积累及果实品质的影响.

Pot culture and field experiments were carried out with one-year-old apple rootstock M9T337 seedlings and five-year-old 'Yanfu3'/SH6/M. hupehensis Rehd. as test materials respectively. Combined with 15N and 13C isotope tracer technology, we examined the effects of different concentrations of NR inhibitor Na2WO4(0, 0.5, 1, 1.5 mmol·L-1, expressed by CK, T1, T2 and T3 respectively) on 15N absorption and 13C accumulation of seedling and apple quality. The results showed that 0.5-1.0 mmol·L-1 Na2WO4 significantly inhibited shoot growth but not root growth of seedling in the pot experiment. Root growth was significantly inhibited when the concentration of Na2WO4 reached 1.5 mmol·L-1. The NR activity of each treatment was negatively correlated with the concentrations of Na2WO4 in the same period, with an order of CK>T1>T2>T3. The content of nitrate in leaves showed the trend of first rising and then decreasing with the extension of processing time. Nitrate content was positively correlated with Na2WO4 concentration in the same period, with an order of T3>T2>T1>CK. Spraying Na2WO4 reduced the 15N absorption of each organ and 15N utilization rate, with such effects increasing with the amount of spraying. With the increases of Na2WO4 concentration, 13C accumulation on the ground increased first and then decreased, with highest value in T2 treatment. The 13C accumulation of whole plant showed a similar pattern. The results of field experiment showed that Na2WO4 application reduced nitrogen contents of leaves and fruits at maturity stage, and increased the anthocyanin content in peel, soluble solids, soluble sugar content and sugar acid ratio in fruits. The T2 treatment showed the best effect. In summary, T2 treatment (1.0 mmol·L-1 Na2WO4) could inhibit shoot growth of seedlings, reduce 15N absorption and utilization, improve 13C accumulation, which would improve apple quality.

[Effects of potassium levels on translocation of 13C-photoassimilates to fruit in 'Fuji' apple during fruit expanding period].

A field experiment was carried out in a six-year old 'Fuji'3/M26/Malus hupehensis Rehd. apple with the 13C tracer method to examine the changes of chlorophyll fluorescence parameters, photosynthetic characteristics of leaf, sugar transporter gene expression, 13C assimilation capability and the characteristics of translocation and distribution of 13C-photoassimilates to fruit under different levels of potassium addition (K2O 0, 0.5%, 1.0%, 1.5%, 2.0%, expressed by CK, K1, K2, K3, K4, respectively). Potassium aqueous solution smear the leaves within 20 cm around the fruit at fruit enlargement stage. Compared with other treatments, K3 treatment significantly increased Rubisco enzyme activity, net photosynthetic rate, maximal photochemical efficiency of PSII, actual photochemical efficiency of PSII, coefficient of photochemical quenching, sorbitol and sucrose content, sorbitol 6-phosphate dehydrogenase (S6PDH) and sucrose phosphate synthase (SPS) enzyme activities and 13C assimilation capability of leaves. Furthermore, K3 treatment increased gene expression of sorbitol transporter MdSOT1 and MdSOT2 and sucrose transporter MdSUT4, and promoted the unloading of sugar in fruit. The 13C of self retention (self leaves and self branches) was the highest in CK (82.6%) and the lowest in K3 treatment (60.5%). With increasing potassium concentration, the 13C absorption of fruit first increased and then decreased, which was the highest in K3 treatment (1.31 mg·g-1) and the lowest in CK (0.57 mg·g-1). Our results indicated that foliage application of potassium solution improved PSII photochemical efficiency, activities of key enzymes related with carbon assimilation, synthesis ability, and outward transport ability of photosynthates in leaves, and consequently promoted the directional transportation of sugar to fruit. The amount of photoassimilates transported to fruit was the most under 1.5% K2O treatment (K3).

[Effects of different integration of water and fertilizer modes on the absorption and utilization of nitrogen fertilizer and fruit yield and quality of apple trees].

We examined nitrogen use efficiency of 15N-urea of 15-year-old 'Gala' apple trees by broadcast fertilization (T1), nitrogen fertilization with drip irrigation (T2) and nitrogen fertilization with subsurface irrigation (T3), to further improve the water and fertilizer integration technology for apple orchard and to improve nitrogen utilization efficiency. The results showed that leaf area, chlorophyll, and leaf nitrogen content of leaves were significantly higher in T3 treatment than those in T1 and T2 treatments. Soil mineral nitrogen content (20-40 cm) in each period followed the order of T3>T2>T1, while that in 0-20 cm followed an order of T2>T3>T1. The Ndff value at organ level (the contribution rate of the 15N amount absorbed by various organs of the tree to the total nitrogen content of the organ) was the highest in T3 treatment in each period, followed by T2 and T1 treatments. The utilization rate of 15N in the fruit ripening period followed an order of T3>T2>T1. The 15N utilization rate of T3 reached 24.2%, being 1.19 and 1.65 times of T2 and T1, respectively. The 15N distribution rate in the fruits during the fruit maturity stage was the highest in T1 treatment, while that in the storage organs was the highest in T2 treatment and that in the reproduction organs was the highest in T3 treatment. The single fruit weight, yield, soluble solids, hardness, soluble sugar and sugar-acid ratio were the highest in T3 treatment, followed by T2 and T1 treatments. In summary, nitrogen application by percolation irrigation (subsurface application) significantly promoted leaf growth and nitrogen utilization of apple tree, and improved fruit yield and quality.

[Effects of exogenous ABA on translocation of photosynthate to fruit of Fuji apple during late stage of fruit rapid-swelling.] / å¤–æºè„±è½é ¸å¯¹å¯Œå£«è‹¹æžœæžœå®žè†¨å¤§åŽæœŸå ‰åˆäº§ç‰©å‘æžœå®žè¿è¾“çš„å½±å“.

To clarify the effects and underlying mechanism of ABA on sugar accumulation in apple fruits, 13C trace technique was used to examined the effects of different ABA levels (0, 50, 100 and 150 mg·L-1) and fluoridone (ABA biosynthesis inhibitor) on translocation of photosynthate to fruit during late stage of fruit rapid-swelling in five-year-old 'Yanfu3'/M26/Malus hupehensis Rehd. The results showed that the activities of related enzyme in sugar metabolism, the relative expression of sucrose transporter gene MdSUT1, MdSUT2.2 and sorbitol transporter gene MdSOT3 tended to increase first and then decrease with increasing ABA concentration, with a peak in 100 mg·L-1ABA treatment. Fluridone treatment significantly inhibited the enzymes activities of sugar metabolism and the relative expression of sugar transporters. The treatment of 100 mg·L-1ABA significantly reduced leaf 13C content, increased fruit 13C content and increased the transport rate of photosynthate from leaves to fruits compared with other treatments. Our results indicated that exogenous ABA enhanced sink strength of fruit and promoted the transportation of more photosynthate to fruits, which increased the soluble sugar content in fruits.

[Effects of potassium supply on the growth, photosynthesis and 15N and 13C absorption and utilization of M9T337 seedling.] / ä¾›é’¾æ°´å¹³å¯¹è‹¹æžœç §æœ¨M9T337å¹¼è‹—ç”Ÿé•¿ã€å ‰åˆç‰¹æ€§ä¸Ž15N、13C吸收利用的影响.

Hydroponic experiment was carried out on M9T337 seedlings using 15N and 13C isotope tracer technology to study the effects of different potassium supply levels (K0, K1, K2, K3 and K4 were equivalent to 0, 3, 6, 9 and 12 mmol·L-1, respectively) on the growth, photosynthetic characteristics and 15N and 13C absorption and utilization of M9T337 seedlings. The results showed that dry mass, root length, root surface area, number of tips and root activity of M9T337 seedlings under the K2 level were significantly higher than those under other levels. The net photosynthetic rate (Pn) of leaves increased at low K+ concentration and then decreased with the increases of potassium supply level, and reached the maximum value at K2 treatment (15.5 µmol CO2·m-2·s-1). At the 30th day after treatment, the activities of nitrate reductase (NR) and carbon metabolism enzyme were highest in K2 treatment, and lowest in K0 treatment. With the increases of potassium application rate, the 13C accumulation of seedlings were first increased and then decreased, with the 13C distribution rate of each organ being the most balanced at K2 treatment. There were significant differences in 15N uptake and utilization rate among treatments. 15N uptake and utilization rates of seedlings under K2 treatment were the highest, which were 16.1 mg and 17.9%, respectively. Therefore, too low or too high potassium supply could inhibit seedling root growth and leaf photosynthesis, which was not conducive to carbon and nitrogen absorption. Appropriate potassium supply could improve root activity and net photosynthetic rate, enhance nitrate reductase (NR) and carbon metabolic enzyme activity, and promote carbon and nitrogen metabolism.

[Effects of split combined application of organic-inorganic fertilizers on plant growth, 15N absorption, utilization and loss of Gala apple tree]. / æœ‰æœºæ— æœºè‚¥åˆ†æ¬¡é æ–½å¯¹å˜Žå•¦è‹¹æžœç”Ÿé•¿ã€15N-å°¿ç´ å¸æ”¶åˆ©ç”¨åŠæŸå¤±çš„å½±å“.

Fifteen-year-old 'Gala'/M. hupehensis Rehd. trees and 15N trace technique were used to explore the effects of split combined application of organic-inorganic fertilizers on plant growth, 15N absorption, utilization and loss. The main results were as follows: compared to control, combined application of organic-inorganic fertilizers significantly increased the root-shoot ratio, chlorophyll content, total nitrogen content of leaves and mean fruit mass. The effects of split combined application of organic-inorganic fertilizers treatment were more obvious than one time combined application. Combined application of organic-inorganic fertilizers treatment improved the capacity of 15N derived from fertilizer (Ndff) of different organs, with the effects of split combined application of organic-inorganic fertilizers treatment being more significant. The Ndff value of fruits in different treatments were the highest, followed by leaves, biennial branches, fine roots, large roots and perennial branches, and lowest in trunks. Total N content of plant and 15N-urea utilization rate of the split combined application of organic-inorganic fertilizers treatment were 395.39 g and 28.4% respectively, which were obviously higher than the treatments of one time combined application (342.77 g and 21.1%) and no organic fertilizer application (296.41 g and 14.6%), while 15N loss rate was 51.3%, which was obviously lower than the treatments of one time combined application (57.5%) and no organic fertilizer application (60.6%).

[Effects of nitrogen application levels on translocation and distribution of 13C-photosynthate and 15N to fruit from leaves of apple tree]. / 氮水平对苹果叶片13Cå ‰åˆäº§ç‰©å’Œ15Nå‘æžœå®žè½¬ç§»åˆ†é çš„å½±å“.

A field experiment was carried out in a six-year old 'Fuji3'/M26/Malus hupehensis Rehd. apple with 15N and 13C labeled tracers, to understand 13C assimilation capability and the characteristics of translocation and distribution of 13C-photosynthate and 15N to fruit under different nitrogen application levels (urea 0%, 0.6%, 1.2%, 1.8%, 2.4%, CK, N1, N2, N3, N4, respectively) to smear the leaves within 20 cm around the fruit at late stage of fruit enlargement. The results showed that, with the increases of urea application, the chlorophyll content, nitrogen content, net photosynthetic rate, sorbitol and sucrose content, sorbitol 6-phosphate dehydrogenase (S6PDH) and sucrose phosphate synthase (SPS) activities, 13C assimilation capability of leaves were first increased and then decreased, with the highest value in 1.8% urea smear treatment and the lowest value with the treatment of clear water. The 13C of self retention (self leaves and self branches) was the highest in clear water (81.6%) and the lowest in 1.8% urea smear treatment (63.5%). The 13C was mainly allocated to fruit, followed by unlabeled perennial branch, and the lowest in unlabeled leaves. With the increases of urea application, the 13C absorption of fruit was first increased and then decreased, with the highest value in 1.8% urea smear treatment (1.21 mg·g-1) and the lowest value in clear water (0.51 mg·g-1). The 15N absorption of fruit was enhanced with the increases of urea application. These results indicated that foliage application of urea solution improved translocation and distribution of leaf photosynthate and nitrogen to fruit with varying degrees, which was the highest in 1.8% urea smear treatment and could avoid excessive intake of nitrogen to fruit.

Dynamics of growth and nitrogen accumulation and utilization of young apple trees.

Taking 6-year-old Yanfu3/SH6/Malus hupehensis Rehd. as the test material, the dynamics of plant growth and nitrogen (N) accumulation under seven periods from germination stage to fruit maturity stage were examined by destructive analysis. The absorption, utilization, and distribution of fertilizer N were studied by 15N isotope tracer technique to clarify the N accumulation dynamics of apple trees and the maximum efficiency period of fertilizer N, and to provide theoretical basis for scientific application of N fertilizer. The results showed that the net accumulation of dry matter was 4.51 kg in germination stage (March 25) to fruit maturity stage (210 d after budbreak), with fruit accounting for 66.5%, the leaves and new shoots accounting for 20.2%, and the perennial organs accounting for 13.3%. The dry matter accumulation in 30-60 d after budbreak was the fastest, accounting for 42.9% of the whole treatment period. The fruit dry matter accumulation in 120-180 d after budbreak was the fastest, which accounted for 70% of the whole treatment period. The total N accumulation of the plant was 29.1 g, which increased rapidly in the 30-60 d and 120-180 d after budbreak by 7.2 g and 12.8 g, respectively accounting for 24.7% and 44% of the whole treatment period. The N accumulation of leaves and new shoots was the fastest in 0-60 d after budbreak, which accounted for 69.1% of the whole period. The N accumulation of fruit was the fastest in 120-180 d after budbreak, accounting for 60.8% of the whole period. The N accumulation of the perennial organ decreased first and then increased, and reached the lowest level at 60 d after budbreak. The 15N utilization rate of plant differed significantly in different periods which was at a high level in 30-60 d,120-150 d and 150-180 d after budbreak with 2.3%, 4.1% and 4.0% respectively. The 15N distribution rate in perennial organs in each period showed a high level, that of the new born organ increased first and then decreased which reached the highest level of 38.4% in 30-60 d after budbreak. The fruit reached the highest in 120-150 d and 150-180 d after budbreak by 15.0% and 16.6% respectively. Therefore, the key period of N accumulation in leaves and shoots was 30-60 d after budbreak, and that in fruit was 120-180 d after budbreak. The period with maximum efficiency for fertilizer N was at 30-60 d and 120-180 d after budbreak.

[Effects of different fulvic acid application rates on fruit yield, quality and fate of 15N-urea in 'Red General' apple.] / ä¸åŒé»„è é ¸ç”¨é‡å¯¹'红将军'苹果产量、品质和15N-å°¿ç´ åŽ»å‘çš„å½±å“.

To explore the effects of different fulvic acid application rates on 15N-urea absorption, utilization, residue amount, loss and fruit yield and quality, fifteen-year-old 'Red General'/ Malus micromalus Makino was selected as experiment material by using the 15N-labeled tracer technique. Five treatments were established: single urea (CK), combination of urea and fulvic acid with varied rates (NF1, NF2, NF3 and NF4 represented 75, 150, 300 and 450 kg·hm-2 fulvic acid application rates, respectively). The main results were as follows: the 15N derived from fertilizer (Ndff) in root, one-year-old branch and leaf were displayed with an order of NF3>NF4>NF2>NF1>CK at the fruit maturity stage, and significant difference was observed in Ndff value among the five treatments. The total N content and 15N absorption amount were highest in NF3, followed by NF4, and lowest in CK. Compared with CK, the 15N utilization rate in NF1, NF2, NF3 and NF4 was increased by 14.2%, 33.5%, 64.2% and 50.0%, and the 15N loss rate was decreased by 9.1%, 18.5%, 37.1% and 28.7% respectively. The residue amount of 15N-urea varied across different treatments, and that in 0-60 cm soil layer under combination of urea and fulvic acid was significantly higher than CK, with the highest value occurred in NF3, while it was lower than CK in 60-100 cm soil layer. In comparison with CK treatment, the largest increment of yield per plant and net income appeared in NF3, with an enhancement of 15.8% and 20.2%, respectively. In addition, the fruit hardness, soluble solid and sugar-acid ratio reached the highest value in NF3. Considering the responses of fruit yield and N utilization efficiency, the suitable fulvic acid application rate was 326.41-350.61 kg·hm-2.

[Nitrogen application technology in dwarfed apple trees.] / 矮化苹果氮肥施用技术.

15N trace technique was used to explore the characteristics of 15N-urea absorption, utilization, loss and fruit quality of eight-year-old 'Yanfu3'/M26/Malus hupehensis Rehd. seedlings. There were three different nitrogen fertilization treatments: one-time nitrogen application in spring (1), two times nitrogen application (2), the intensive technique of nitrogen application with several times application and reduction in amount (3). The results showed that leaf area, chlorophyll content (SPAD value), photosynthetic rate (Pn), total N content of leaves and the total biomass per plant (except fruit), as well as the root-shoot ratio of treatment 3 were obviously higher than those in the treatments of 1 and 2. Treatment 3 significantly increased the protective enzymes (SOD, POD and CAT) activities and decreased the malondialdehyde (MDA) content in leaves. Significant differences were found on the 15N derived from fertilizer (Ndff value) of different organs, with the fruit Ndff showing the highest, followed by the one-year-old branches, leaves and roots of the three treatments. The Ndff values of each organ were the highest in the treatment 3. At fruit maturity stage, total N content of plant in treatment 3 was 93.0 mg·kg-1, which was obviously higher than that in the treatments 1 (70.2 mg·kg-1) and 2 (81.9 mg·kg-1). 15N nitrogen utilization ratio of treatment 3 was 33.6%, which was obviously higher than that in the treatments 1 (20.4%) and 2 (26.0%). The 15N loss rate was 46.9% in treatment 3, being obviously lower than that in the treatments 1 (56.5%) and 2 (52.9%). There were significant differences of fruit mass, soluble solid, fruit firmness, soluble sugar content, titratable acids and sugar-acid ratio among different treatments, with the highest values in the treatment 3 and the lowest values in treatment 1.

[Effects of controlled-release nitrogen fertilizer and bag-controlled release fertilizer on utilization of 15N-urea in 'Orin' apple and its accumulation in soil.] / 控释氮肥和袋控肥对'王林'苹果15N-å°¿ç´ åˆ©ç”¨åŠå ¶åœ¨åœŸå£¤ç´¯ç§¯çš„å½±å“.

Taking a six-year old 'Orin' apple tree plantation ('Orin'/SH6/ Malus micromalus Makino) as test material, the effects of common urea treatment (CU), bag-controlled release ferti-lizers treatment (BCRF) and controlled-release nitrogen fertilizer treatment (CRNF) on 15N-urea absorption, utilization, loss and accumulation dynamics of nitrogen content in 0-80 cm soil layer were investigated by 15N labeled tracer method. The results showed that compared with CU treatment, both CRNF and BCRF treatments increased the inorganic nitrogen content in soil at the late stage of apple growth, the leaf SPAD value, leaf nitrogen content, net photosynthetic rate and 15N derived from fertilizer (Ndff value) of different organs at fruit maturity stage, with CRNF showing stronger effects than BCRF. The amount of 15N residue in 0-40 cm soil layer showed a decreasing trend in different phenological stages. The amount of 15N residue was the highest in CRNF, followed by BCRF, and the lowest in CU, among which CRNF declined gently with 15N residue mainly concentrated in the 0-40 cm soil layer. 15N residue in 40-80 cm soil layer showed an increasing trend in different phenological stages, which was the highest in CU, followed by BCRF, and the lowest in CRNF, and that of CRNF increased gently. The 15N fertilizer utilization rate of CRNF was 32.6% at fruit maturity stage, which was 1.11 and 1.56 times as high as that of BCRF and CU, whereas its 15N loss rate was 21.6%, being obviously lower than BCRF (35.6%) and CU (59.6%). CRNF significantly improved fruit yield and quality and increased economic benefits.

[Effects of different phosphorus application rates on growth, 15N-urea absorption, and utilization characteristics of pear rootstocks.] / ä¾›ç£·æ°´å¹³å¯¹æ¢¨ç §æœ¨ç”Ÿé•¿å’Œ15N-å°¿ç´ å¸æ”¶åˆ©ç”¨ç‰¹æ€§çš„å½±å“.

Three kinds of potted one-year-old pear rootstocks (Pyrus calleryana, P. pashia, and P. xerophila) and 15N trace technique were used to examine the effects of different phosphorus application rates (P0, P1, P2, P3 and P4 equivalent to 0, 50, 100, 150 and 200 kg·hm-2 P2O5, respectively) on plant growth and the characteristics of 15N-urea absorption and utilization. The results showed that, with the increases of phosphorus levels, plant height, ground diameter, dry mass, root surface area, root length, number of root tips, root activity, root respiration rate, Ndff values, and nitrogen use efficiency of rootstocks first increased and then decreased. However, the range of rise and fall of different rootstocks were distinct, and each index reached the highest level at different phosphorus levels. The plant height, diameter, dry mass of P. xerophila were the highest under the same phosphorus level, followed by P. pashia, and P. calleryana was the lowest. The root architecture parameters and root respiration rate showed the same trend, but Ndff values and nitrogen use efficiency performed different. Under different phosphorus levels, each index of P. xerophila reached the highest level at P3, but those of P. pashia and P. calleryana appeared at P2 and P1 rates, respectively. The Ndff values in stem were the highest among different organs of rootstocks at diffe-rent phosphorus levels, and the highest nitrogen use efficiency of P. xerophila, P. pashia and P. calleryana was 9.6%, 8.9% and 8.3%, respectively. The variations of plant growth and N absorption and utilization of different pear rootstocks across different phosphorus levels indicated that phosphorus fertilizer should be carry out reasonably in practice and give full consideration of phosphorus demands of plants.

[Fate of fertilizer nitrogen and soil nitrogen pool budget of Fuji apple from germination stage to new shoot growing stage]. / 富士苹果萌芽至新梢旺长期肥料氮去向和土壤氮库盈亏.

15N trace technique were used to explore the fertilizer nitrogen (N) absorption and utilization, soil residue and soil nitrogen pool budget under different nitrogen fertilization levels (0, 50, 100, 150, 200, 250 kg·hm-2) for five-year-old 'Yanfu 3'/SH6/M. hupehensis Rehd. from germination stage to new shoot growing stage. The results showed that 15N were preferentially distributed to the roots and then transported to aboveground for the construction of new organs after N application in early spring. After the end of new shoot growing (two months later after N application), 5.9%-9.9% of fertilizer N was absorbed by apple tree, 29.8%-33.4% of fertilizer N was resided in 0-60 cm soil, and 56.7%-64.4% of fertilizer N was lost. With the increases of N application rate, the amount of fertilizer N absorbed by trees and the amount of soil residual N gradually increased, the utilization ratio of fertilizer N and soil residual ratio decreased, and the loss and the loss ratio of N were increased. With the increases of N application rates, the total balance of soil N changed from deficit to surplus, and the surplus increasing significantly with the increases of N application rates. The results indicated that low N application rate could cause a decrease of soil N fertility and the excessive application of nitrogen could increase the accumulation of N and increase the risk of N pollution. Fertilizer N levels showed a significant linear correlation with soil total N balance, with the regression equation being y=0.3511x-20.808 (R2=0.9927). In the stages from germination to new shoot growing, soil N pool reached balance when the N application rate was 59.27 kg·hm-2.

[Effects of nitrate nitrogen supply on the growth, photosynthetic characteristics and 15N absorption, utilization of Malus hupehensis seedlings.] / ç¡é ¸ç›ä¾›åº”æ°´å¹³å¯¹å¹³é‚‘ç”œèŒ¶å¹¼è‹—ç”Ÿé•¿ã€å ‰åˆç‰¹æ€§ä¸Ž15N吸收、利用的影响.

To explore the effects of different nitrate nitrogen levels (N0, N1, N2, N3 and N4 were equivalent to 0, 2.5, 5, 10, 20 mmol·L-115NO3- -N, respectively) on the growth, photosynthetic characteristics and 15N absorption, utilization and distribution, Malus hupehensis seedlings were grown in cultural liquid Hoagland by using the 15N-labeled tracer method. The results showed that the leaf chlorophyll content, leaf area and dry mass in different organs were the highest in N2 treatment. With the increase of 15NO3- -N application rates, the leaf net photosynthetic rate (Pn)significantly increased but tended to decease when the 15NO3--N concentration exceeded N2 treatment. In the 20th day after treatment, the root activity, root length, root surface area and number of tips of seedlings in N2 treatment were significantly higher than those in the other treatments. The distribution ratio of 15N in different organs was significantly different among those treatments. The relatively balanced distribution ratio of 15N appeared in N2 treatment, which the 15N utilization rate also reached relatively higher level. The total N content and 15N absorption of seedlings increased at low 15NO3--N concentration, reached the highest value in N2 treatment with 103.77 and 21.57 mg, and then deceased at high 15NO3--N concentration. At the 12th day after treatment, the leaf nitrate reductase (NR) activity was the highest in N2 treatment and the lowest in N4 treatment. The leaf nitrate reductase (NR) activity deceased by 84.9% in N4 treatment compared with N2 treatment at the 16th day after treatment. Our findings indicated that the photosynthesis and absorption of nitrate nitrogen were inhibited under low 15NO3--N stress, and the assimilation of nitrate nitrogen and root growth were restrained under too much higher 15NO3--N level, which was not good for the growth, nitrogen absorption and utilization of apple seedlings. The appropriate nitrogen level could promote plant growth, enhance the photosynthesis and also increase the absorption, utilization and distribution of nitrogen.

Improving the Accuracy of the Hyperspectral Model for Apple Canopy Water Content Prediction using the Equidistant Sampling Method.

The influence of the equidistant sampling method was explored in a hyperspectral model for the accurate prediction of the water content of apple tree canopy. The relationship between spectral reflectance and water content was explored using the sample partition methods of equidistant sampling and random sampling, and a stepwise regression model of the apple canopy water content was established. The results showed that the random sampling model was Y = 0.4797 - 721787.3883 × Z3 - 766567.1103 × Z5 - 771392.9030 × Z6; the equidistant sampling model was Y = 0.4613 - 480610.4213 × Z2 - 552189.0450 × Z5 - 1006181.8358 × Z6. After verification, the equidistant sampling method was verified to offer a superior prediction ability. The calibration set coefficient of determination of 0.6599 and validation set coefficient of determination of 0.8221 were higher than that of the random sampling model by 9.20% and 10.90%, respectively. The root mean square error (RMSE) of 0.0365 and relative error (RE) of 0.0626 were lower than that of the random sampling model by 17.23% and 17.09%, respectively. Dividing the calibration set and validation set by the equidistant sampling method can improve the prediction accuracy of the hyperspectral model of apple canopy water content.

[Effects of nitrogen-supply levels on leaf senescence and characteristics of distribution and utilization of 13C and 15N in Fuji 3 apple grafted on different stocks]. / ä¾›æ°®æ°´å¹³å¯¹ä¸åŒç §ç©—ç»„åˆè‹¹æžœå¶ç‰‡è¡°è€åŠ13C、 15Nåˆ†é åˆ©ç”¨çš„å½±å“.

Two-year-old potted Fuji 3 apple trees on different rootstocks [Fuji 3/M. micromalus Makin (joe), Fuji 3/M7 (semi-dwarf) and Fuji 3/M26/M. micromalus Makin (dwarf)] were used to study leaf morphology and photosynthesis and the characteristics of distribution and utilization of 13C and 15N at different nitrogen supply levels (0N, 25%N and 100%N, the N content in 100% N treatment was the same as that in Hoagland complete nutrient solution) under sand culture condition. The main results were as follows: At shoot growth cessation stage in autumn, the leaf chlorophyll content (SPAD), leaf nitrogen content and photosynthetic rate were found the highest in Fuji 3/M. micromalus Makin, followed by Fuji 3/M7, and the lowest was found in Fuji 3/M26/M. micromalus Makin under the same nitrogen stress treatments (0N and 25%N), however, under normal nitrogen treatment (100%N) Fuji 3/M26/M. micromalus Makin had the highest leaf SPAD value, photosynthetic rate and the nitrogen content, followed by Fuji 3/M7, and the lowest was found in Fuji 3/M. micromalus Makin. The leaf SOD and CAT activities showed Fuji 3/M. micromalus Makin > Fuji 3/M7 > Fuji 3/M26/M. micromalus Makin under the same nitrogen stress treatments, but showed Fuji 3/M26/M. micromalus Makin > Fuji 3/M7 > Fuji 3/M. micromalus Makin under the normal nitrogen treatment. There were significant differences in the distributions of 15N and 13C in root and leaf in the 3 scion-stock combinations, and the distribution rates of 15N and 13C in roots were the highest under nitrogen stress treatments and in the order of Fuji 3/M. micromalus Makin > Fuji 3/M7 > Fuji 3/M26/M. micromalus Makin. The distribution rates of 15N and 13C in leaves were the highest under the normal nitrogen treatment and in the order of Fuji 3/M26/M. micromalus Makin > Fuji 3/M7 > Fuji 3/M. micromalus Makin. The 15N utilization ratio differed significantly among the 3 scion-stock combinations under different nitrogen application levels and was in the order of Fuji 3/M. micromalus Makin (44.3%, 37.5% and 31.4%)> Fuji 3/M7 (38.8%,30.7% and 26.6%) > Fuji 3/M26/M. micromalus Makin (32.0%,27.2% and 22.5%).

[Effects of different nitrogen application rates on 15N-urea absorption, utilization, loss and fruit yield and quality of dwarf apple]. / 供氮水平对矮化苹果15N-å°¿ç´ å¸æ”¶ã€åˆ©ç”¨ã€æŸå¤±åŠäº§é‡å’Œå“è´¨çš„å½±å“.

Seven-year-old 'Yanfu3'/M26/M. hupehensis Rehd. seedlings and 15N trace technique were used to explore the characteristics of 15N-urea absorption, utilization, loss and fruit yield and quality under different nitrogen application rates (N100, N200 and N300). The main results were as follows: the plant growth, 15N absorption, utilization and loss differed significantly under different treatments. The plant leaf chlorophyll content (SPAD value), photosynthetic rate (Pn), total N content of leaves and the biomass, as well as the root-shoot ratio of N200 treatment were obviously higher than the N100 and N300 treatments. Significant differences were observed in the 15N derived from fertilizer (Ndff value) of different organs under different nitrogen application rates. The Ndff of fruits (flowers), leaves, one-year-old branch, and perennial branches in each measurement period was N100 >N200＞N300, while that of the roots at full-bloom and spring shoot growing slowly stage was N100 >N200＞N300, and in a trend of N200 >N100＞N300 at autumn shoot growing stage, fruit rapid-swel-ling stage and fruit maturity stage. At fruit maturity stage, plant 15N nitrogen utilization ratio of N200 treatment was 23.6%, which was obviously higher than the N100 (16.3%) and N300 (14.4%) treatments, with the 15N loss rate of 56.4%, obviously lower than the N100 (60.6%) and N300 (66.1%) treatments. There were significant differences among the treatments in fruit mass, yield per plant, soluble solid, fruit firmness, soluble sugar, titratable acids and sugar-acid ratio of different nitrogen rates, and the N200 treatment showed the best performance, followed by the N300 treatment, and then the N100 treatment.

[Effects of different potassium levels on growth and NO3- uptake and utilization of Malus hupehensis seedlings]. / 不同供钾水平对平邑甜茶幼苗生长及NO3-吸收利用特性的影响.

In order to explore the effects of potassium fertilizer on the absorption and utilization of nitrogen fertilizer, and provide theoretical basis for scientific fertilization in apple orchard, Malus hupehensis seedlings were used to study the effects of different potassium levels (K0, K1, K2, K3, K4, K5, and K6 equivalent to 0, 2, 4, 6, 8, 10, and 12 mmol·L-1 K+, respectively) on growth and NO3- uptake and utilization using the track technology of 15N and non-damage microtest technique. The results showed that root vigor, nitrate reductase activity and root morphological index of seedlings in K3 treatment were significantly higher than those in the other treatments. The 15N derived from fertilizer (Ndff) in different organs of M. hupehensis seedlings was significantly different among treatments, and the Ndff values of root, stem and leaf appeared in K3 treatment were the highest, being 1.36, 1.33 and 1.47 times as those of the K0 treatment, respectively. With the increase of potassium application rate, the 15N utilization rate of seedlings were firstly increased and then decreased, and reached the highest value (23.3%) in K3 treatment, which was 3.04 times as that of K0 treatment. The results of non-damage microtest technique showed that there was a strong absorption of NO3- in K3 treatment (19.34 pmol·cm-2·s-1), while a clear trend of outflow was observed in the potassium deficiency (K0) and high potassium (K6) treatments. Therefore, the deficit or excess of potassium could inhibit the uptake and utilization of nitrogen, while appropriate potassium could promote root growth, enhance the activity of nitrate reductase, and then increase the absorption of nitrogen by seedlings.