A method for evaluating the branch pulling of a pear tree based on a growth model

Abstract

The present application relates to the field of arbor pear management, and discloses a kind of arbor pear branch pulling evaluation method based on growth model construction.The present application takes the arbor pear of "double-arm forward type" as research object, and carries out branch pulling treatment to its 1-year-old new shoot, detects the length and thickness of new shoot and the growth situation of fruit related indexes, establishes linear or nonlinear regression equation, and analyzes the dynamic trend of fruit quality formation under different treatment conditions.The test results of the present application prove that, under the arbor cultivation mode, different branch treatment angles are closely related to the output efficiency of reserve carbon "source" (shoot, leaf) to "sink" (fruit) and growth potential.In 95-110 days after flowering, coordinating and enhancing the nutrition management of shoot and fruit can be beneficial to simultaneously guarantee the formation of fruit quality in later period and stable tree potential.The present application can provide theoretical basis for formulating reasonable technical measures for the standardization and fine management of 'Cui Guan' arbor pear tree body.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pear tree planting management, and particularly relates to a shed pear tree branch pulling evaluation method based on a growth model. BACKGROUND

[0002] Pear is one of the world's five major fruits, and is the largest fruit tree species in China after apple and citrus. At present, the pear orchard cultivation area in China is about 1.0047 million hectares, accounting for 70.85% of the world's pear cultivation area, ranking first in the world. With the sharp rise in labor costs, the cultivation mode of pear has changed from traditional manual management to labor-saving, mechanized and automated mode. Therefore, it is an inevitable trend to develop a simple, high-quality and high-yield tree management mode. In recent years, the "double-arm forward type" pear shed cultivation technology with the characteristics of labor-saving, machine-friendly and high quality has attracted much attention. Under the new cultivation mode, how to evaluate the influence of different artificial management methods on the growth state of fruit trees has become an important issue.

[0003] It is known that branch pulling is a practical way to inhibit vegetative growth, enhance canopy light interception and improve fruit tree productivity. Due to the inherent growth habit, different varieties have different physiological responses to different pulling times or angles, resulting in different distribution results of long and short branches in different parts or quantities. In the shed cultivation mode of pear, the growth of fruiting branches is controlled within a relatively fixed size, which has an important influence on the expansion of the tree crown. At the same time, the number and length, thickness of fruiting branches on the trunk determine the recovery potential of the branches and trunk to a certain extent, control the number and attachment points of leaves, and are the basis for fruit formation this year or next year, and also the basis for further shaping the tree shape by pruning, so it is of great practical significance to select the appropriate pulling angle.

[0004] There are few reports on the research of pear tree growth model in the prior art, especially on the new type of shed cultivation mode "double-arm forward type" pear tree with strong growth polarity symmetry, and there are few reports on the influence of branch pulling on the branch characteristics and fruit quality. SUMMARY

[0005] The purpose of the present application is to provide a shed pear tree branch pulling evaluation method based on a growth model. The present application takes the "double-arm forward type" shed pear tree as the research object, and the 1-year-old new shoots are subjected to branch pulling treatment. The length and thickness of the new shoots and the growth of the fruit are detected, a linear or nonlinear regression equation is established, and the dynamic trend of fruit quality formation under different treatment conditions is analyzed. The present application can provide a theoretical basis for formulating reasonable technical measures for the standardization and fine management of 'Cui Guan' shed pear tree.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions: a method for evaluating the pulling of branches of trellis pear trees based on a growth model, comprising the following steps:

[0007] Step 1: Select a double-arm progressive pear tree in a trellis cultivation mode, select appropriate branches for pulling branches at different angles for different test groups, and then fix them on the trellis;

[0008] Step 2: Determination of branch characteristics. The initial sprouting day of the shoot is defined as the initial growth day 0, marked as D0. The length and thickness of the newly sprouted shoots on the branches are measured and recorded at regular intervals.

[0009] Step 3: Determination of fruit quality indexes: Pick fruits according to the test groups and measure the fruit quality indexes;

[0010] Step 4: Data processing and growth model construction. Draw a logistic regression graph of the growth process of branch length and thickness. With date as x and branch length / thickness as y, the characteristic value of new shoot growth is calculated according to equations (1)-(6).

[0011]

[0012] Where: y is the length or thickness of the shoot; t is the growth time of the shoot; k is the theoretical maximum value of the shoot growth length; a and b are parameters; t1 is the start time of rapid growth of the shoot; t2 is the end time of rapid growth of the shoot; v m is the maximum relative growth rate; t m is the time of maximum relative growth. t1 and t2 are the two points with the fastest daily growth rate, i.e., the dividing point from germination to rapid growth to slow growth. t2-t1 is the peak growth period.

[0013] A scatter plot of fruit quality indices was drawn and univariate analysis was performed. Correlation analysis was performed using the Pearson method, and differences between mean values ​​were assessed using the LSD test (P < 0.05). The peak flowering period was defined as day 0 of fruit development and growth. The number of days after peak flowering was defined as x, and the fruit indices were defined as 'y'. The growth rate equations corresponding to the fruit indices were obtained by online derivation. The inflection point was predicted using -b / 2a (for quadratic equations) and the second-order derivative f"(x) = 0 (for cubic equations).

[0014] Step 5: The growth model of shoot length and diameter under different branch pulling angles was constructed. Equation (1) was used to fit the growth data of shoot length and diameter of the experimental group under different branch pulling conditions. The fitting curve was obtained. The correlation coefficient exceeded 0.9, indicating that the correlation between the fitting equation and the measured data reached an extremely significant level. The constructed Logistic model has a relatively reliable predictive reference for the development process of new shoots during this growth period.

[0015] Step six, new shoot growth stage division under different pulling branch angles, using equations (3) (4) (5) (6) to calculate the branch shoot growth rate inflection point and other phenological parameters, the growth of new shoot length and thickness can be divided into three stages of initial growth (0, t1), rapid growth period (t1, t2), and late growth (t2, t n ) three stages;

[0016] Step seven, evaluating the change of new shoot length and thickness growth rate under different pulling branch angles, determining whether there is significant difference between different test groups in each growth stage;

[0017] Step eight, mathematical equation model construction of fruit growth under different pulling branch angles, using one-dimensional quadratic equation and one-dimensional cubic equation to fit the related index of fruit and the number of days after full bloom;

[0018] Step nine, comparing the quality characteristics of mature fruits under different pulling branch angles, comparing whether there is obvious difference between different test groups of each fruit index.

[0019] The further setting of the application is that in step one, the branch selection method is that: at the position of 1.0-2.0 m away from the center trunk of each tree, 1-year-old branches with the same orientation, similar thickness and length and natural growth angle are selected for pulling branches with different angles, and the angles are 60°, 30° and 0°.

[0020] The further setting of the application is that in step two, the length and thickness of newly sprouted branches on the branches are measured and recorded every 6-10 days, the length is measured by a fixed ruler, the diameter is measured by an electronic vernier caliper, and then the growth thickness is calculated according to the area formula.

[0021] The further setting of the application is that in step three, the Cui Guan fruits without obvious mechanical damage and pests and diseases are picked according to the test groups, the fruit quality is weighed by an electronic balance, the fruit length and width are measured by a vernier caliper, the fruit shape index is calculated, the fruit shape index = maximum longitudinal diameter / maximum transverse diameter; the fruit hardness is measured by a fruit hardness meter at the maximum transverse diameter of the fruit, 3 times are measured for each group, and the average value is taken; the soluble solid content is measured by a sugar tester; the titratable acid content is measured by an acidimeter, each sample is measured 3 times, and the average value is taken.

[0022] The further setting of the application is that in step four, the k value is determined according to the three-point rule, the observation values (t a ,y a ), (t b ,y b ) and (t c ,y c ) are taken, so that:

[0023]

[0024] The further setting of the present application is that in step four, the fast growth duration T (T=t2-t1), the growth initial stage Fast growth stage Growth late stage According to the k value and the y value, a series of y' values corresponding to different time points are obtained, then a straight line regression equation is fitted with time as the horizontal coordinate and y' as the vertical coordinate, and R 2 Value.

[0025] The further setting of the present application is that in step eight, the five growth indexes of the fruit growth process in each test group, including the transverse diameter, the sugar content, the hardness, the weight and the longitudinal diameter, are analyzed, the sugar content, the weight and the longitudinal diameter indexes are fitted by using a quadratic equation, and the transverse diameter and the hardness indexes are fitted by using a cubic equation, and the corresponding fitting models are constructed.

[0026] The further setting of the present application is that in step eight, the curves are drawn according to the time points of 78d, 87d, 100d, 112d, 119d and 127d after flowering.

[0027] The beneficial effects of the present application are that the present application takes the 'double-arm forward type' shed frame pear tree as the research object, carries out the branch pulling treatment (T1=60°, T2=30°, T3=0°) on the one-year-old new shoots, detects the length and thickness of the new shoots and the growth situation related indexes (fruit weight, transverse diameter, longitudinal diameter, hardness, sugar content, titratable acid, sugar acid ratio) of the fruit, establishes the linear or nonlinear regression equation, and analyzes the dynamic trend of the fruit quality formation under different treatment conditions. The test results of the present application prove that under the shed frame cultivation mode, different branch treatment angles are closely related to the output efficiency of the reserve carbon'source' (branch, leaf) to'sink' (fruit) and the growth potential of the pear tree. It is possible to benefit the formation and stable tree potential of the fruit quality in the later period by coordinating and enhancing the nutrition management of the branch and the fruit within 95-110 days after flowering. The present application can provide a theoretical basis for formulating reasonable technical measures for the standardization and fine management of the 'Cui Guan' shed frame pear tree. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is the test design schematic diagram of the present application, and the shed frame is the pear tree B before being put on the frame.

[0029] Figure 2 is the shed frame that makes the pear tree different branch pulling angle treatment schematic diagram of the present application.

[0030] Figure 3is the growth length (A) and thickness (B) fitting curve of the one-year-old new shoots of the ‘Cuiguan’ double-arm pear tree of the present application, T1 = 60° branch pulling treatment, T2 = 30° branch pulling treatment, T3 = 0° branch pulling treatment, and each point represents the average value of the branch and shoot growth determination results of the T1-T3 treatment groups.

[0031] Figure 4 is the fruit longitudinal diameter variation law of the present application.

[0032] Figure 5 is the fruit transverse diameter growth dynamic variation law of the present application.

[0033] Figure 6 is the fruit weight dynamic variation law of the present application.

[0034] Figure 7 is the fruit soluble solid dynamic variation law of the present application.

[0035] Figure 8 is the fruit hardness dynamic variation law of the present application.

[0036] Figure 9 is the difference in fruit quality of the ‘Cuiguan’ pear under different branch pulling angles of the present application. DETAILED DESCRIPTION

[0037] EMBODIMENT

[0038] 1. MATERIALS AND METHODS

[0039] 1.1. Overview of the Test Site

[0040] The test site is located in Jiangxia District, Wuhan City, Hubei Province, and is located in the transition section from the Jianghan Plain to the E'nan Hilly region. The soil type is yellow-brown soil, the altitude is 30 m (N 30°17'24"E 114°8'55"), and it belongs to subtropical monsoon climate. The annual average temperature is between 15.9-17.9℃, and the annual average precipitation is 1260.6 mm.

[0041] 1.2. Test Material

[0042] The test was carried out in the double-arm in-line shed pear test base of the Fruit and Tea Institute of Hubei Academy of Agricultural Sciences. The test tree species were all 1-year-old seedling grafts planted in January 2019, the test variety was ‘Cuiguan’ (Pyrus pyrifolia nakai cv. Cuiguan), the pollination variety was ‘Wonhwang’ (P. pyrifolia Nakai cv. Wonhwang), and the ‘Cuiguan’ double-arm model pear trees with healthy and uniform tree vigor were selected and labeled. Standardized water and fertilizer management was carried out in accordance with the “Double-arm pear” technical regulations.

[0043] 1.3. Test Design

[0044] Three experimental plots were set up in the plantation, each plot including 8-9 ‘CuiGuan’ trees with healthy growth and uniform vigor (a1, 9 trees; a2, 9 trees; a3, 8 trees), totaling 26 trees Figure 1 A), and the branches were pulled and placed on the shelf in early February 2023 (see Figure 1 B). Branch selection method: At a distance of 1.0-2.0 m from the center trunk on both arms of each tree, 1-year-old branches with similar orientation, thickness, and length were selected for different angle pulling, with angles of 60° (T1), 30° (T2), and 0° (T3) (i.e., nearly parallel to the ground), and then placed on the shelf and fixed (see Figure 2 ). The number of branches pulled for each angle treatment on each tree was 10-15, and the measurement position was marked. The thickness measurement point was about 3 cm from the base of the branch, and the length was the distance from the base to the terminal bud. The length and thickness of the newly sprouted shoots were measured and recorded every 6-10 days.

[0045] 1.4 Experimental methods

[0046] 1.4.1 Branch trait determination

[0047] The initial sprouting of CuiGuan branches in 2023 occurred on March 18, which was defined as the initial growth day 0, marked as D0. The flowering period was on March 20, which was defined as the 0th day of fruit development growth. According to the branch hanging number on the test tree, the length and diameter of the newly sprouted shoots were measured and recorded. The length was measured with a fixed ruler, and the diameter was measured with an electronic vernier caliper, and then the growth thickness was calculated according to the area formula (i.e., cross-sectional area of branch base, CSAB), S = π·(d / 2) 2 .

[0048] 1.4.2 Fruit quality index determination

[0049] CuiGuan fruits without obvious mechanical damage and pests were picked according to the experimental groups, and the fruit quality was determined. The fruit quality was determined by electronic balance, and the fruit shape index was calculated (fruit shape index = maximum longitudinal diameter / maximum transverse diameter). The fruit hardness was measured using a GY-4 type digital fruit hardness meter (Zhejiang Topuynong Technology Co., Ltd.), and the average value was taken for each group. The soluble solid content was measured using a PAL-1 portable digital sugar meter [produced by ATAGO (Ato) Scientific Instruments Co., Ltd., Japan], and the titratable acid content was measured using a PAL-Easy portable digital acidity meter [produced by ATAGO (Ato) Scientific Instruments Co., Ltd., Japan]. Each sample was measured 3 times, and the average value was taken.

[0050] 1.5 Data processing and growth model construction

[0051] Data were processed by Excel 2013, and the Logistic model of branch growth was calculated according to the following equation. The Logistic regression graph of branch length and thickness growth process was drawn by Origin 9.0 software (with date as x and branch length / thickness as y), and the characteristic value of new shoot growth was calculated according to equations (1)-(6). The scatter plot of fruit weight, transverse diameter, longitudinal diameter, hardness, etc. was drawn by GraphPad 8 software, and single factor analysis of variance (ANOVA) was performed on it by SPSS 20.0 software. Pearson method was used for correlation analysis, and LSD test was used to evaluate the difference between the mean values (P<0.05). The growth rate equation of each fruit index was obtained by online derivation using WolframAlpha, and the inflection point prediction used-b / 2a (for quadratic equation) and second derivative f''(x)=0 (for cubic equation).

[0052]

[0053]

[0054] The value of k was determined according to the three-point rule. The observation values (t a ,y a ), (t b ,y b ) and (t c ,y c ) were taken at equal intervals, so that:

[0055]

[0056] The duration of rapid growth T (T=t2-t1), the initial growth Rapid growth period Late growth According to the value of k and y, a series of y' values corresponding to different time points were obtained. Then the time was taken as the horizontal coordinate and y' as the vertical coordinate, and the linear regression equation was fitted, and the r 2 value was obtained.

[0057] In the formula: y is the length or thickness of the branch; t is the growth time of the branch; k is the theoretical maximum value of the length of the branch growth; a and b are parameters; t1 is the starting time of rapid growth of the branch; t2 is the termination time of rapid growth of the branch; v m is the maximum relative growth rate; t m is the time when the maximum relative growth rate occurs. t1 and t2 are the two points with the fastest rate of change in consecutive days, i.e. the dividing point from germination to rapid growth into slow growth, and t2-t1 is the peak growth period.

[0058] 2 Results and Analysis

[0059] 2.1 New shoot length and diameter growth model construction under different pulling angles

[0060] The growth of new shoot length and diameter of‘Pyrus x bretschneideri’ under different pulling angles could be fitted by equation(1), and the growth curves of length and diameter were shown in Fig.1 and Fig.2, respectively. Figure 1 It could be seen that the new shoot growth showed a S-shaped trend of“slow-fast-slow(stable)”under different pulling angles. The growth data of new shoot length and diameter under different pulling angles were fitted, and the correlation coefficients were all more than 0.9, which indicated that the correlation between the fitted equation and the measured data reached a very significant level, and the theoretical extreme value k was very close to the measured value(see Table 1). Therefore, the constructed Logistic model had a reliable prediction reference for the development process of new shoot in this growth period.

[0061] 2.2 New shoot growth stage division under different pulling angles

[0062] According to the calculation of equation(3), (4), (5), (6) in 1.4 data processing, the inflection point of shoot growth rate and other phenological parameters were calculated(Table 2), and the growth of new shoot length and diameter could be divided into three stages: early growth stage(0, t1), rapid growth stage(t1, t2), and late growth stage(t2, t n ). The results showed that, in terms of length growth, although the inflection point of T1 group entering the rapid growth stage was delayed by about 2d(4 / 16) compared with T2 and T3(4 / 14), there was no significant difference in the length of early growth stage, rapid growth stage, and the maximum relative growth rate v m also had no significant difference(P>0.05). In terms of diameter development, the termination time t2 of rapid growth of T3 group was significantly less than that of T1 and T2 groups(P<0.05), and the length of rapid growth stage was also significantly shorter than that of T1 and T2 groups(P<0.05), which meant that T3 group entered the slow growth state earliest.

[0063] Table 1 Logistic model parameters and test indexes of‘Cui Guan’ new shoot growth under‘Pyrus x bretschneideri’ tree shape mode

[0064]

[0065] (Note: the p value of each group of data above is less than 0.01, the unit of length is cm, and the unit of diameter is mm 2 )

[0066] Meanwhile, it can be seen from the table that the starting time of rapid growth (t1) of length growth gradually advances with the decrease of pulling angle in different treatments; on the contrary, the starting time of rapid growth of diameter growth gradually delays. In the characteristics of diameter growth, the inflection point of the appearance time of maximum relative growth (t3) of T3 group is nearly one week (6.14 d) earlier than that of T1, and the maximum relative growth rate v m of the former is about 2.02 times faster than that of the latter, and the overall performance is T3>T2>T1, but this trend is not significant in length growth (P>0.05).

[0067] Table 2 New shoot length and diameter growth characteristics values

[0068]

[0069] t1 is the starting time of rapid growth, d; t2 is the ending time of rapid growth, d; v m is the maximum relative growth rate; t m is the appearance time of maximum relative growth, d. The new shoot length and diameter growth values of the three groups (a1, a2, a3) of pear trees are shown as the average value ± standard error of each treatment (n=30-45 branches / treatment). Different letters in each column indicate significant differences between treatments (P<0.05).

[0070] 2.3 Changes of new shoot length and diameter growth rate under different pulling angle

[0071] The "double-arm forward type" shed frame pear tree has the important feature of symmetrical growth distribution of branches and leaves in the east-west or north-south direction, and the growth rate of the shoots on the main branches determines the sustainable expansion structure of the crown to a certain extent. Table 4 shows that in the early growth stage, there is no significant difference in the average growth rate of length among the three groups (P>0.05), and the average growth rate of diameter of T3 is significantly higher than that of T1 and T2; in the rapid growth period, the average growth rate of length is T2>T1>T3, and there is a significant difference between T3 and T2 (P<0.05), and the average growth rate of diameter of T3 is significantly higher than that of T1 and T2, which is similar to the case in the early growth stage; in the late growth stage, the average growth rate of length is T2>T1>T3, and there is a significant difference between T3 and T2 (P<0.05), and the average growth rate of diameter shows the trend of T3>T2>T1, and there is a significant difference among the three (P<0.05). Overall, in terms of the growth rate of length, there is no significant difference between T1 and T3 in the three periods, and the average growth rate of T2 is relatively high in the rapid growth period and the late growth period. However, in terms of diameter growth, T3 is significantly higher than T1 and T2, especially in the late growth period.

[0072] Table 3 New shoot length and diameter growth development process

[0073]

[0074] Table 4. Comparison of average growth rate of shoot length and diameter

[0075]

[0076] The shoot length and diameter growth rate values of the three zones (a1, a2, a3) of pear trees are shown as the average values ± standard error of each treatment (n = 30-45 branches / treatment). Different letters within each column indicate significant differences between treatments (P < 0.05). The starting calculation day t0=0 was set on March 18, and the end of the growth period was August 1, t0=0.

[0077] 2.4 Construction of mathematical equation models for fruit growth at different pulling angles

[0078] The use of quadratic and cubic equations for fitting fruit-related indicators with days has good fitting degree and can study the change rules of related indicators during the fruit growth period. By analyzing the growth of five indicators such as horizontal diameter, sugar content, hardness, weight, and vertical diameter during the fruit growth process under three different angle treatments, curves were drawn according to the time points of 78 d (June 7), 87 d (June 16), 100 d (June 29), 112 d (July 11), 119 d (July 18), and 127 d (July 26) after flowering.

[0079] The quadratic equation was used to fit the sugar content, weight, and vertical diameter, and the cubic equation was used to fit the horizontal diameter and hardness indicators and construct the corresponding fitting models, and the related parameters are shown in Table 5. The results show that the weight, vertical diameter, and horizontal diameter have a higher data fitting degree, R 2 The fitting degree is close to 0.90. The corresponding fitting curve and derivative function graph are as follows Figure 2As shown in the figure, the fitting curves for fruit transverse diameter showed similar trends for T1, T2, and T3. Over time, the transverse diameter of the fruit increased, while the growth rate showed a decreasing trend for all three treatments. The fitting curves for fruit sugar content showed similar trends for T1, T2, and T3. The growth rate of T3 was lower than that of T1 and T2 in the early stage, but exceeded that of T1 and T2 in the later stage. The growth rate of sugar content in T1 and T2 showed a decreasing trend, while that of 90° showed an increasing trend. The fitting curves for fruit firmness showed similar trends for T1 and T3, showing a positive U-shaped curve, while the fitting curve for T2 showed a negative U-shaped curve. Over time, the firmness of the fruit increased. The growth rate showed an increasing trend for T1 and T3, while that of T2 showed a slow decreasing trend. The fitting curves for fruit weight and longitudinal diameter showed similar trends for T1, T2, and T3. Over time, the weight and longitudinal diameter of the fruit increased, while the growth rate showed a decreasing trend for all three treatments.

[0080] Table 5 Fruit growth model parameters and test indicators at different branch pulling angles

[0081]

[0082] 2.5 Comparison of quality characteristics of mature fruits at different branch pulling angles

[0083] Fruit weight and longitudinal and transverse diameter values ​​can directly reflect the size of a single fruit. Comparing the relationship between single fruit weight, fruit shape index, transverse diameter, longitudinal diameter, soluble solids, titratable acid, sugar-acid ratio and flesh hardness of fully mature 'Cui Guan' fruits at different branch pulling angles, we found that ( Figure 9 ), single fruit weight, fruit shape index, transverse diameter, longitudinal diameter, and soluble sugar content did not differ significantly under the three branch pulling angles (p>0.05); for titratable acid, there was no significant difference between the T2 and T3 groups, and the average titratable acid content of the T1 group was significantly higher than that of the T2 and T3 groups (p<0.05); in terms of sugar-acid ratio, there was no significant difference among T2, T1, and T3, while the average sugar-acid ratio of the Cuiguan fruit grown under the T3 treatment was significantly higher than that of the T1 group (p<0.05), but not significantly different from that of T2; in terms of flesh firmness, the Cuiguan fruit grown under the T2 and T3 conditions were significantly lower than that of the T1 treatment group (p<0.05). Comparing these indicators, the overall quality of the Cuiguan fruit in the T3 group was better than that of the T1 and T2 groups.

[0084] Tree structure is the key of orchard management, and branch pulling is an important method to change tree structure. It plays an important role in improving tree light-receiving, inhibiting vegetative growth, inducing flower bud sprouting and promoting fruit secondary metabolite accumulation. The relationship between plant branch or fruit growth index and development time is an effective means to evaluate tree growth, fruit yield and quality by using Logistic equation and polynomial regression method. In this study, the curve fitting equation and derivative function constructed by shoot length and thickness can accurately reflect the growth dynamics of branch, and provide a prediction idea for the growth or decline of orchard branch. Meanwhile, the relationship between shoot growth rate and fruit quality formation was preliminarily determined by comparing the effects of three branch pulling angles on fruit quality formation.

[0085] In the early stage of shoot growth and fruit growth of ‘Cui Guan’ pear, the growth rhythm and trend of the two were basically consistent. The peak period of shoot growth was also accompanied by the peak period of fruit growth. From mid-April to mid-May, the length of the shoot grew rapidly, and the length growth of the shoot accounted for more than 90% of the annual shoot height growth. Figure 1 After entering June, the shoot growth of each treatment group was slow, and the growth of length and thickness appeared a temporary period. The thickness growth was relatively not obvious, but it maintained a relatively long period of time. This may be due to the shift of tree nutrient allocation from vegetative growth to fruit reproductive growth, which was more typical in T3 group (0°). This indicated that the fruit growth of ‘Cui Guan’ pear relied on the growth of new shoots to form more leaves to produce nutrients, and under the management condition of branch pulling to inhibit vegetative growth, this trend was more obvious with the decrease of branch pulling angle.

[0086] The length of the shoot under three angle treatments showed the growth characteristics of “S” curve, while the thickness growth of T1 and T2 groups showed a relatively flat trend, and T3 group showed a typical “S” type. The results showed that different branch pulling angles affected the biomass of new shoot sprouting, and the effect on the growth rate of shoot thickness was much greater than that of length. From the length development, T3 group entered the rapid growth period earliest, which was 2-3 days earlier than T1 group. From the thickness development, T3 group entered the rapid growth period latest, which was about 2-3 days later than T1 group. At the same time, it can be seen from the table that the initial time of length growth rapid growth was increasingly advanced with the decrease of branch pulling angle. In the thickness growth characteristics, the maximum relative growth rate v m The inflection point of the maximum relative growth rate v mwhich was 2.02 times faster than T3, and the overall trend was T3>T2>T1, but this trend was not obvious in length growth (Table 2). For fruit quality, by testing the fruits of Tsugumi after full ripening, it was found that although there was no significant difference in soluble sugar content among the three treatments, the titratable acid content of T1 group (0.21% ± 0.07%) was significantly higher than that of T2 (0.19% ± 0.04%) and T3 (0.18% ± 0.04%), and the sugar-acid ratio showed a trend of T3>T2>T1. Correspondingly, the average growth rate of branch cross-sectional area in the late growth period of the three treatment groups was T3 (11.69 mm 2 / d)>T2 (10.54 mm 2 / d)>T1 (9.47 mm 2 / d), which further suggested that, due to the pulling of the branches in the T3 group, the length of the branches entered the rapid growth period earlier, the maximum relative growth rate of the thickness (cross-sectional area) growth was higher, and the growth stopped relatively early (72.16 d), which was beneficial to the rapid output of carbon "source" (stem, leaf) to "sink" (fruit), so that the organic acid (malic acid, citric acid, etc.) in the pulp cells completed the transformation and accumulation to sugar compounds in advance, and therefore the sugar-acid ratio was relatively significantly increased ( Figure 3 ), at the same time, it also promoted the accelerated transport of important mineral elements such as calcium, so the pulp hardness was relatively lower. This may imply that pulling the branches can mainly change the radial transport (the direction of the diameter of the branch cross section) of nutrients rather than the axial (perpendicular to the direction of the branch cross section) to regulate the growth and development of pear fruiting branches, thereby affecting the synthesis and transport of secondary metabolic compounds in the pulp.

Claims

1. A method for evaluating branch pulling of trellis pear trees based on a growth model, characterized by: The following steps are included: Step 1: Select a double-arm progressive pear tree in a trellis cultivation mode, select appropriate branches for pulling branches at different angles for different test groups, and then fix them on the trellis; Step 2: Determination of branch characteristics. The initial sprouting day of the shoot is defined as the initial growth day 0, marked as D0. The length and thickness of the newly sprouted shoots on the branches are measured and recorded at regular intervals. Step 3: Determination of fruit quality indexes: Pick fruits according to the test groups and measure the fruit quality indexes; Step 4: Data processing and growth model construction. Draw a logistic regression graph of the growth process of branch length and thickness. With date as x and branch length / thickness as y, the characteristic value of new shoot growth is calculated according to equations (1)-(6). Where: y is the length or thickness of the shoot; t is the growth time of the shoot; k is the theoretical maximum value of the shoot growth length; a and b are parameters; t1 is the start time of rapid growth of the shoot; t2 is the end time of rapid growth of the shoot; v m is the maximum relative growth rate; t m is the time of maximum relative growth; t1 and t2 are the two points with the fastest daily growth rate, i.e., the dividing point from germination to rapid growth to slow growth, and t2-t1 is the peak growth period; Determine the k value according to the three-point rule, take the observation value of t equal distance (t a ,y a )、(t b ,y b ) and (t c ,y c ),make: Rapid growth duration T (T = t2-t1), initial growth Rapid growth period Late growth period ( ~after), according to the k value and y value, a series of y corresponding to different time points are obtained ′ value, and then use time as the horizontal axis, y ′ As the vertical coordinate, fit the linear regression equation and get R 2 value Step 5: The growth model of shoot length and diameter under different branch pulling angles was constructed. Equation (1) was used to fit the growth data of shoot length and diameter of the experimental group under different branch pulling conditions to obtain the fitting curve. Step 6: The growth stages of new shoots under different branch pulling angles are divided. Equations (3)(4)(5)(6) are used to calculate the inflection point of shoot growth rate and other phenological parameters. The growth of new shoot length and thickness can be divided into the early growth stage (0, t1), the rapid growth stage (t1, t2), the late growth stage (t2, t3), and the rapid growth stage (t4, t5). n ) three stages; Step 7: Evaluate the changes in the growth rate of new shoot length and diameter at different branch pulling angles to determine whether there are significant differences between different experimental groups at each growth stage; Step 8: Constructing a mathematical equation model for fruit growth at different branch pulling angles, using a quadratic equation and a cubic equation to fit fruit-related indicators and the number of days after full flowering; Step nine: Compare the quality characteristics of mature fruits at different branch pulling angles to see if there are significant differences between different test groups in various fruit indicators.

2. The method for evaluating branch pulling of trellis pear trees based on a growth model according to claim 1, characterized in that: In step one, the branch selection method is: at a position of 1.0 to 2.0 m from the central trunk of each tree's arms, select one-year-old branches with the same orientation, similar thickness and length and natural growth angles for pulling branches at different groups of angles, namely 60°, 30°, and 0°.

3. The method for evaluating branch pulling of trellis pear trees based on a growth model according to claim 1, characterized in that: In step 2, the length and thickness of newly sprouted shoots on the branches are measured and recorded every 6-10 days. The length is measured with a fixed ruler and the diameter is measured with an electronic vernier caliper. The thickness of the growth is then calculated according to the area formula.

4. The method for evaluating branch pulling of trellis pear trees based on a growth model according to claim 1, characterized in that: In step three, Cuiguan fruits without obvious mechanical damage and pests and diseases were picked according to the experimental groups, the fruit weight was weighed with an electronic balance, the longitudinal and transverse diameters of the fruit were measured with a vernier caliper, and the fruit shape index was calculated, which was the maximum longitudinal diameter / maximum transverse diameter. The fruit hardness was measured with a fruit hardness meter at the part with the maximum transverse diameter of the fruit, and the hardness of the peeled flesh was measured at the part with the largest transverse diameter of the fruit. Each group was measured three times, and the results were averaged. The soluble solids content was measured with a sugar meter; the titratable acid content was measured with an acidity meter. Each sample was measured three times, and the average value was taken.

5. The method for evaluating branch pulling of trellis pear trees based on a growth model according to claim 1, characterized in that: In step eight, the five growth indices of the fruit during growth, namely, transverse diameter, sugar content, hardness, weight, and longitudinal diameter, were analyzed in each experimental group. The sugar content, weight, and longitudinal diameter indices were fitted with a quadratic equation, and the transverse diameter and hardness indices were fitted with a cubic equation, and corresponding fitting models were constructed.

6. A method for evaluating branch pulling of trellis pear trees based on a growth model according to claim 1 or 5, characterized in that: In step eight, curves are drawn according to the time points of 78 days, 87 days, 100 days, 112 days, 119 days and 127 days after full flowering.

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