Shed frame pear tree branch pulling evaluation method based on growth model construction

Abstract

The invention relates to the field of trellis pear tree management, and discloses a trellis pear tree branch pulling evaluation method constructed based on a growth model. According to the method, a'two-arm forward-moving 'trellis pear tree is taken as a research object, one-year new tips of the pear tree are subjected to branch pulling treatment, a linear or nonlinear regression equation is established by detecting relevant indexes of the length and the thickness of the new tips and the growth condition of fruits, and the dynamic trend of fruit quality formation under different treatment conditions is analyzed. Test results of the method prove that in a shed frame type cultivation mode, different branch processing angles are closely related to output efficiency and growth vigor of reserve carbon sources (branches and leaves) of pear trees to libraries (fruits). The nutrition management of the branches and the fruits can be coordinated and enhanced within 95-110 days after blooming, so that the formation of the fruit quality and the stabilization of the tree vigor in the later period can be ensured at the same time. According to the method, a theoretical basis can be provided for formulating reasonable technical measures for standardized and refined management of the Cuiguan shed frame pear tree bodies.

Description

Technical Field

[0001] The invention relates to the technical field of pear tree planting and management, and in particular to a trellis pear tree branch pulling evaluation method based on a growth model. Background Art

[0002] Pear is one of the five major fruits in the world, and is also the fruit tree species with the largest cultivation area in China after apples and citrus. At present, the cultivated area of ​​pear orchards 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 pears has changed from traditional human management to labor-saving, mechanized and automated methods. Therefore, it has become an inevitable trend to develop a light, simple, high-quality and high-yield tree management model. In recent years, the "double-arm forward-moving" pear trellis cultivation technology, which has the characteristics of labor-saving, machine-friendly and high-quality, has attracted much attention. Under the new cultivation model, how to evaluate the impact of different manual management methods on the growth status of fruit trees has become an important topic.

[0003] It is known that branch pulling is a practical way to inhibit vegetative growth, enhance canopy light interception, and improve fruit tree productivity. Affected by their inherent growth habits, different varieties have different physiological responses to different branch pulling times or angles, resulting in different positions or quantities of long and short branches. In the trellis pear cultivation model, since the growth of fruiting branches is controlled at a relatively fixed scale, it has an important impact on the expansion of the crown. At the same time, the number, length, and thickness of the fruiting branches on the trunk determine the recovery potential of the branches to a certain extent, control the number and attachment points of the leaves, are the basis for fruit formation in the current or next year, and are also the basis for pruning fruit trees to further shape the tree shape. Therefore, choosing a suitable branch pulling angle is of great practical significance.

[0004] There are few reports on the research on pear tree growth models in the existing technology, especially on the "double-arm progressive" pear trees with a new trellis cultivation model with strong growth polarity symmetry. There are few reports on the effects of pulling branches on their branch characteristics and fruit quality. Summary of the invention

[0005] The purpose of the present invention is to provide a method for evaluating the branch pulling of trellis pear trees based on a growth model. The present invention takes the "double-arm progressive" trellis pear trees as the research object, performs branch pulling on the one-year-old new shoots, and detects the length and thickness of the new shoots and the growth-related indicators of the fruit, establishes a linear or nonlinear regression equation, and analyzes the dynamic trend of the fruit quality formation under different treatment conditions. The present invention can provide a theoretical basis for formulating reasonable technical measures for the standardized and refined management of the 'Cui Guan' trellis pear trees.

[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 the double-arm forward-moving pear tree in the trellis cultivation mode, select appropriate branches to pull 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 branch is defined as the initial growth day 0, marked as D0. The length and thickness of the newly sprouted branch on the branch are measured and recorded at regular intervals.

[0009] Step 3: Determination of fruit quality indexes: picking fruits according to the test groups and measuring 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 branch; t is the growth time of the branch; k is the theoretical maximum value of the growth length of the branch; a and b are parameters; t1 is the start time of rapid growth of the branch; t2 is the end time of rapid growth of the branch; 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;

[0013] The scatter plot of fruit quality indexes was drawn, and single factor analysis was performed on it. Pearson's method was used for correlation analysis, and the difference between the mean values ​​was evaluated using LSD test (P<0.05). The full flowering period was defined as the 0th day of fruit development and growth. The number of days after full flowering was x, and the fruit index was 'y. The growth rate equation corresponding to each fruit index was obtained by online derivation. The inflection point prediction used -b / 2a (applicable to quadratic equations) and the second-order derivative f″(x)=0 (applicable to cubic equations);

[0014] Step 5: construct the growth model of new shoot length and thickness under different branch pulling angles. Use equation (1) to fit the growth data of new shoot length and thickness of the experimental group under different branch pulling conditions to obtain the fitting curve. The correlation coefficient exceeds 0.9, indicating that the correlation between the fitting equation and the measured data reaches 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 6: The growth stages of new shoots under different branch pulling angles are divided. Equations (3), (4), (5), and (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), and the late growth stage (t2, t n ) three stages;

[0016] Step 7, evaluate the changes in the growth rate of new shoot length and thickness under different branch pulling angles, and determine whether there are significant differences between different test groups at each growth stage;

[0017] Step 8: constructing a mathematical equation model of fruit growth under 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;

[0018] Step nine, compare the quality characteristics of mature fruits at different branch pulling angles, and compare whether there are significant differences between different test groups of various fruit indicators.

[0019] The present invention is further configured as follows: in step one, the branch selection method is: at a position where the arms of each tree are 1.0 to 2.0 m away from the central trunk, 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, which are 60°, 30°, and 0° respectively.

[0020] The present invention is further configured as follows: 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, the diameter is measured with an electronic vernier caliper, and then the thickness of the growth is calculated according to the area formula.

[0021] The present invention is further configured as follows: in step 3, Cuiguan fruits without obvious mechanical damage and pests and diseases are picked according to the test groups, the fruit weight is weighed with an electronic balance, the longitudinal and transverse diameters of the fruit are measured with a vernier caliper, and the fruit shape index is calculated, where the fruit shape index = maximum longitudinal diameter / maximum transverse diameter; the fruit hardness is measured by a fruit hardness meter at the part with the maximum transverse diameter of the fruit, and each group is measured 3 times, and the results are averaged; the soluble solid content is measured by a sugar meter; the titratable acid content is measured by an acidometer, and each sample is measured 3 times, and the average value is taken.

[0022] The present invention is further configured as follows: in step 4, the k value is determined according to the three-point rule, and the observation value (t a ,y a )、(t b ,y b ) and (t c ,y c ),make:

[0023]

[0024] The present invention is further configured as follows: in step 4, the rapid growth duration is T (T = t2-t1), the initial growth period is Rapid growth period Late growth According to the k value and the y value, a series of y' values ​​corresponding to different time points are obtained, and then the linear regression equation is fitted with time as the horizontal axis and y' as the vertical axis, and R is obtained. 2 value.

[0025] The present invention is further configured as follows: in step eight, five growth indices of the transverse diameter, sugar content, hardness, weight and longitudinal diameter of the fruit during growth in each test group are analyzed, the sugar content, weight and longitudinal diameter indices are fitted with a quadratic equation, the transverse diameter and hardness indices are fitted with a cubic equation, and corresponding fitting models are constructed.

[0026] The present invention is further configured as follows: in step eight, curves are drawn according to the time points of 78d, 87d, 100d, 112d, 119d and 127d after full flowering.

[0027] The beneficial effects of the present invention are as follows: the present invention takes the "double-arm forward-moving" trellis pear tree as the research object, and carries out branch pulling treatment (T1=60°, T2=30°, T3=0°) on its one-year-old new shoots, and detects the length and thickness of the new shoots and the growth-related indicators of the fruit (fruit quality, horizontal diameter, vertical diameter, hardness, sugar content, titratable acid, sugar-acid ratio), establishes a linear or nonlinear regression equation, and analyzes the dynamic trend of fruit quality formation under different treatment conditions. The test results of the present invention prove that under the trellis cultivation mode, different branch treatment angles are closely related to the output efficiency and growth potential of the pear tree's reserve carbon "source" (shoots, leaves) to the "sink" (fruit). Coordinating and enhancing the nutritional management of shoots and fruits within 95-110 days after full flowering may be beneficial to simultaneously ensure the formation of late fruit quality and stabilize the tree potential. The present invention can provide a theoretical basis for formulating reasonable technical measures for the standardized and refined management of the 'Cui Guan' trellis pear tree body. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the experimental design of the present invention A, and the trellis before being put on the shelf is a pear tree B.

[0029] Figure 2 It is a schematic diagram of the trellis of the present invention for processing pear trees at different branch pulling angles.

[0030] Figure 3This is the growth fitting curve of the one-year-old new shoot growth length (A) and thickness (B) of the 'Cui Guan' double-arm pear tree of the present invention, 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 growth measurement results of the T1-T3 treatment groups.

[0031] Figure 4 It is the variation rule of the longitudinal diameter of the fruit of the present invention.

[0032] Figure 5 This is the dynamic change rule of the fruit transverse diameter growth of the present invention.

[0033] Figure 6 This is the dynamic variation rule of the fruit weight of the present invention.

[0034] Figure 7 This is the dynamic change rule of the fruit soluble solids of the present invention.

[0035] Figure 8 This is the dynamic change rule of the fruit hardness of the present invention.

[0036] Fig. 9 It is the difference in the quality of the Cuiguan fruit of the present invention at different branch pulling angles. DETAILED DESCRIPTION

[0037] Example

[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, at the transition zone from Jianghan Plain to southern Hubei hills. The soil type is yellow-brown soil. The altitude is 30m (N 30°17'24″E 114°8'55″). It has a subtropical monsoon climate, with an average annual temperature between 15.9 and 17.9℃ and an average annual precipitation of 1260.6mm.

[0041] 1.2 Test materials

[0042] This experiment was conducted at the Double-arm Prograde Trellis Pear Experimental Base of the Fruit and Tea Research Institute of Hubei Academy of Agricultural Sciences. The experimental trees were all planted in January 2019 (one-year-old seedling rootstock grafted seedlings), the participating varieties were 'Cuiguan' (Pyruspyrifolia nakai cv. Cuiguan), and the pollination variety was 'Yuanhuang' (P.pyrifolia Nakaicv. Wonhwang). The 'Cuiguan' double-arm model pear trees with strong and uniform tree vigor were selected for listing, and standardized water and fertilizer management was carried out in accordance with the "Double-arm Pear" technical regulations.

[0043] 1.3 Experimental design

[0044] The plantation was divided into three experimental areas, each area including 8-9 strong and uniform 'Cui Guan' trees (a1, 9 trees; a2, 9 trees; a3, 8 trees), a total of 26 trees ( Figure 1 A), and put them on the shelves in early February 2023 (see Figure 1 B). Branch selection method: At a distance of 1.0 to 2.0 m between the arms of each tree and the central trunk, select one-year-old branches of the same orientation, similar thickness and length and with natural growth angles for pulling branches at different angles, namely 60° (T1), 30° (T2), and 0° (T3) (i.e. nearly parallel to the ground), and then fix them on the rack (see Figure 2 As shown in the figure). For each angle treatment, 10 to 15 branches were pulled from each tree, and the measurement positions were marked. The thickness measurement point was about 3 cm from the base of the branch, and the length was the distance from the base of the branch to the top bud. The length and thickness of the newly sprouted branches on the branches were measured and recorded every 6-10 days.

[0045] 1.4 Experimental methods

[0046] 1.4.1 Determination of branch traits

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

[0048] 1.4.2 Determination of fruit quality indicators

[0049] Cuiguan fruits without obvious mechanical damage and pests were picked according to the test groups, and the fruit weight was weighed with an electronic balance, and the longitudinal and transverse diameters of the fruit were measured with a vernier caliper to calculate the fruit shape index (fruit shape index = maximum longitudinal diameter / maximum transverse diameter). The fruit hardness was measured using a GY-4 digital fruit hardness meter (Zhejiang Top Yunnong Technology Co., Ltd.) at the maximum transverse diameter of the fruit. Each group was measured 3 times, and the results were averaged. The soluble solids content was measured using a PAL-1 portable digital sugar meter [produced by ATAGO (Ai Tuo) Scientific Instrument Co., Ltd., Japan]; the titratable acid content was measured using a PAL-Easy portable digital acidity meter [produced by ATAGO (Ai Tuo) Scientific Instrument 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] Excel 2013 was used to organize the data, 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 using Origin 9.0 software (with date as x and branch length / thickness as y), and the characteristic values ​​of new shoot growth were calculated according to equations (1)-(6). GraphPad 8 software was used to draw scatter plots of fruit weight, horizontal diameter, vertical diameter, hardness, etc. SPSS 20.0 software was used to perform one-way analysis of variance (ANOVA), Pearson method was used for correlation analysis, and LSD test was used to evaluate the difference between mean values ​​(P<0.05). With the number of days after full flowering as x and the various fruit indicators as 'y, WolframAlpha was used for online derivation to obtain the growth rate equation corresponding to each fruit indicator. The inflection point prediction used -b / 2a (applicable to quadratic equations) and the second-order derivative f″(x)=0 (applicable to cubic equations).

[0052]

[0053]

[0054] Determine the value of k according to the three-point rule. Take t equally spaced observations (t a ,y a )、(t b ,y b ) and (t c ,y c ),make:

[0055]

[0056] Rapid growth duration T (T = t2-t1), initial growth Rapid growth period Late growth According to the k value and y value, a series of y' values ​​corresponding to different time points are obtained. Then, with time as the horizontal axis and y' as the vertical axis, a linear regression equation is fitted to obtain r 2 value.

[0057] Where: 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 growth length of the branch; a and b are parameters; t1 is the start time of rapid growth of the branch; t2 is the end time of rapid growth of the branch; 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, that is, the dividing point from germination to rapid growth to slow growth, and t2-t1 is the peak growth period.

[0058] 2 Results and analysis

[0059] 2.1 Construction of new shoot length and thickness growth model at different branch pulling angles

[0060] The growth of new shoot length and thickness of trellis pear can be fitted by formula (1), where the length and thickness growth fitting curves are shown in Figure 1 It can be seen that the new shoots under different branch pulling conditions show an S-shaped growth trend of "slow-fast-slow (stable)". The new shoot length and thickness growth data of other treatment groups under different branch pulling conditions were fitted, and the correlation coefficients were all over 0.9, indicating that the correlation between the fitting equation and the measured data reached an extremely significant level, and the theoretical extreme value k was also very close to the measured value (see Table 1). Therefore, the constructed Logistic model has a more reliable predictive reference for the development process of new shoots during this growth period.

[0061] 2.2 Division of new shoot growth stages at different branch pulling angles

[0062] According to formulas (3), (4), (5), and (6) in the data processing of 1.4, the inflection point of shoot growth rate and other phenological parameters (Table 2) can be calculated. The growth of new shoot length and thickness can be divided into the early growth period (0, t1), the rapid growth period (t1, t2), the late growth period (t2, t n The results generally showed that in terms of length growth, although the turning point of the T1 group entering the rapid growth period was delayed by about 2 days (April 16) compared with T2 and T3 (April 14), there was no significant difference in the length of the initial growth period and the rapid growth period among the three treatments. The maximum relative growth rate v m There was no significant difference (P>0.05). In terms of thickness development, the end time t2 of rapid growth in the T3 group was significantly shorter than that in the T1 and T2 groups (P<0.05), and the duration of the rapid growth period was also significantly shorter than that in the T1 and T2 groups (P<0.05), which means that the T3 group entered the slow growth state the earliest.

[0063] Table 1 Logistic model parameters and test indicators of new shoot growth of 'Cui Guan' under the 'Shuangbi Pear' tree shape model

[0064]

[0065] (Note: The p values ​​of the above processed data are all less than 0.01, length unit: cm, thickness unit: mm 2 )

[0066] At the same time, it can be seen from the table that under different treatments, as the branch pulling angle decreases, the rapid growth start time (t1) of length growth tends to be gradually advanced; on the contrary, the rapid growth start time of thickness growth tends to be gradually delayed. In the thickness growth characteristics, the maximum relative growth time inflection point (t3) of the T3 group is nearly one week earlier than that of the T1 group (6.14 days), and the maximum relative growth rate v m It was about 2.02 times faster than the latter, and the overall performance was T3>T2>T1, but this trend was not significant in length growth (P>0.05).

[0067] Table 2 Characteristic values ​​of new shoot length and thickness growth

[0068]

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

[0070] 2.3 Changes in the growth rate of new shoot length and thickness at different branch pulling angles

[0071] The "double-arm forward-type" trellis pear tree has a main axis in the east-west or north-south direction, and has an important feature of symmetrical growth distribution of branches and leaves. The growth rate of the shoots on the main branches determines the sustainable expansion structure of its crown width to a certain extent. Table 4 shows that in the early growth period, there was no significant difference in the average growth rate of length among the three groups (P>0.05), and the average growth rate of thickness T3 was significantly higher than that of T1 and T2 groups; in the rapid growth period, the average growth rate of length T2>T1>T3, and there was a significant difference between T3 and T2 (P<0.05), and the average growth rate of thickness T3 was significantly higher than that of T1 and T2 groups, which was similar to the situation in the early growth period; in the late growth period, the average growth rate of length T2>T1>T3, and there was a significant difference between T3 and T2 (P<0.05), and the average growth rate of thickness showed a trend of T3>T2>T1, and there were significant differences among the three (P<0.05). In general, in terms of the growth rate of length growth, there was no significant difference between the T1 and T3 groups in the three periods, and the average growth rate of T2 was relatively high in the rapid growth period and the late growth period. However, in terms of thickness growth, the T3 group was significantly greater than the T1 and T2 groups, especially in the late growth period.

[0072] Table 3 Growth process of new shoot length and thickness

[0073]

[0074] Table 4 Comparison of average growth rate of new shoot length and thickness

[0075]

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

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

[0078] The quadratic equation and cubic equation were used to fit the fruit-related indexes with the number of days, which had a good fitting degree and could also study the changing rules of the related indexes in the fruit growth cycle. The five growth indexes of the fruit growth process, including the horizontal diameter, sugar content, hardness, weight and vertical diameter, were analyzed under three different angles, and the curves were drawn according to the time points of 78d (June 7), 87d (June 16), 100d (June 29), 112d (July 11), 119d (July 18) and 127d (July 26) after full bloom.

[0079] The sugar content, weight, and longitudinal diameter were fitted by a quadratic equation, and the transverse diameter and hardness were fitted by a cubic equation to construct the corresponding fitting model. The relevant parameters are shown in Table 5. The results show that the weight, longitudinal diameter, and transverse diameter have higher data fitting degrees, and R 2 The fitting degree is close to 0.90. The corresponding fitting curve and derivative function graph are as follows Figure 2As shown. From the perspective of the fruit transverse diameter fitting curve, the trends of the T1, T2, and T3 fitting curves are basically similar. As time goes by, the fruit transverse diameter increases, and from the perspective of the growth rate, the increase rate of the three treatment groups shows a downward trend; from the perspective of the fruit sugar content fitting curve, the trends of the T1, T2, and T3 fitting curves are basically similar. The growth rate of the T3 fitting curve is lower than that of T1 and T2 in the early stage, but exceeds that of T1 and T2 in the later stage. From the perspective of the growth rate, the growth rate of the sugar content of T1 and T2 fruits shows a downward trend, while 90° shows an upward trend; from the perspective of the fruit hardness fitting curve, the trends of the T1 and T3 fitting curves are basically similar, showing a positive "U" shape, and the trend of the T2 fitting curve shows a negative "U" shape. As time goes by, the fruit hardness increases, and from the perspective of the growth rate, the increase rate of T1 and T3 shows an upward trend, while T2 shows a slow downward trend; from the perspective of the fruit weight and longitudinal diameter fitting curves, the trends of the T1, T2, and T3 fitting curves are basically similar. As time goes by, the fruit weight and longitudinal diameter increase, and from the perspective of the growth rate, the three treatments show a downward trend.

[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. 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 was compared. Fig. 9 ), single fruit weight, fruit shape index, horizontal diameter, vertical diameter and soluble sugar content were not significantly different under the three branch pulling angles (p>0.05); for titratable acid, there was no significant difference between T2 and T3 groups, and the average titratable acid content of T1 group fruit was significantly higher than that of T2 and T3 groups (p<0.05); in terms of sugar-acid ratio, there was no significant difference between T2 and T1 and T3, while the average sugar-acid ratio of Cuiguan fruit grown under T3 group treatment was significantly higher than that of T1 group (p<0.05), but not significantly different from T2; compared with the flesh hardness, Cuiguan fruit under T2 and T3 conditions were significantly lower than that of T1 treatment group (p<0.05). Comparing these indicators, the comprehensive quality of Cuiguan fruit in T3 group was better than that of T1 and T2 groups.

[0084] Tree structure is the key to orchard management and production. Branch pulling is an important means to change tree structure. It plays an important role in improving tree light, inhibiting vegetative growth, inducing flower bud initiation, and promoting the accumulation of secondary metabolites in fruits. Using the Logistic equation and polynomial regression method to analyze the relationship between plant branch or fruit growth indicators and development time is an effective means to evaluate tree growth, fruit yield and quality. In this study, the curve fitting equation and derivative function constructed by using branch length and thickness can accurately reflect the branch growth dynamics, providing a prediction method for the growth or decline of fruiting branches of trellis pears. At the same time, by comparing and analyzing the effects of three branch pulling angles on fruit quality formation, the relationship between branch growth rate and fruit quality formation was preliminarily clarified.

[0085] In the early stage of branch growth and fruit growth of 'Cui Guan' pear, the growth rhythm and trend of the two are basically consistent. The peak period of branch growth also ushered in the peak period of fruit growth. From mid-April to mid-to-late May, the length of branches grows rapidly, and the length growth of branches during this period can account for more than 90% of the annual branch height growth ( Figure 1 ). After June, the branches of each treatment group grew slowly, and the growth of length and thickness showed a temporary suspension period. The growth of thickness was relatively unobvious, but it lasted for a relatively long period of time, which may be attributed to the fact that the focus of tree nutrient distribution shifted from vegetative growth to fruit reproductive growth. This situation was more typical under the conditions of the T3 group (0°). This shows that the fruit growth of 'Cui Guan' depends on the growth of new shoots to form more leaves to produce nutrients, and under the management conditions of pulling branches down to inhibit vegetative growth, this trend becomes more obvious as the pulling angle decreases.

[0086] The branch lengths under the three angle treatments all showed the growth characteristics of an "S" curve, while in terms of thickness growth, the trends presented by the T1 and T2 groups were relatively gentle, while the T3 group showed a very typical "S" shape. The results showed that different branch pulling angles affected the biomass of new branches, and had a much greater impact on the growth rate of branch thickness than on length. From the perspective of length development, the T3 group entered the rapid growth period the earliest, 2-3 days earlier than the TI group; and from the perspective of thickness development, the T3 group entered the rapid growth period the latest, about 2-3 days later than the T1 group. At the same time, it can be seen from the table that the start time of rapid growth in length is increasingly advanced as the branch pulling angle decreases. In the characteristics of thickness growth, the maximum relative growth rate v m The turning point in the T3 group appeared nearly a week earlier than that in the T1 group, and the maximum relative growth rate v mIt was 2.02 times faster than the latter, and the overall performance was T3>T2>T1, but this trend was not obvious in length growth (Table 2). As for fruit quality, by testing the fully mature Cuiguan fruits, it was found that although there was no significant difference in the soluble sugar content of the fruits under the three treatments, the titratable acid content of the T1 group (0.21%±0.07%) was significantly higher than that of the T2 (0.19%±0.04%) and T3 groups (0.18%±0.04%), and the sugar-acid ratio showed a trend of T3>T2>T1. Correspondingly, the average growth rate of the cross-sectional area of ​​the branches of the three treatment groups in the late growth period was T3 (11.69mm 2 / d)>T2(10.54mm 2 / d)>T1(9.47mm 2 / d), which can be further speculated that under the branch pulling conditions of the T3 group, the branch length entered the rapid growth period earlier, the maximum relative growth rate of the thickness (cross-section) was higher, and the growth stopped relatively early (72.16d), which was conducive to the rapid output of the reserve carbon "source" (stem and leaf) to the "sink" (fruit), so that the organic acids in the pulp cells (malic acid, citric acid, etc.) were converted and accumulated into sugar compounds in advance, so the sugar-acid ratio was relatively significantly improved ( Figure 3 ), and at the same time, it also promotes the accelerated transport of important mineral elements such as calcium, so the flesh is relatively less hard. This may suggest that branch pulling may regulate the growth and development of pear fruiting branches mainly by changing the radial transport of nutrients (in the direction of the branch cross-section diameter) rather than the axial direction (perpendicular to the branch cross-section), thereby affecting the synthesis and transport of secondary metabolites in the flesh.

Claims

1. A method for evaluating the pulling of branches of trellis pear trees based on a growth model, characterized in that: The following steps are included: Step 1: Select the double-arm forward-moving pear tree in the trellis cultivation mode, select appropriate branches to pull 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 branch is defined as the initial growth day 0, marked as D0. The length and thickness of the newly sprouted branch on the branch are measured and recorded at regular intervals. Step 3: Determination of fruit quality indexes: picking fruits according to the test groups and measuring 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 branch; t is the growth time of the branch; k is the theoretical maximum value of the growth length of the branch; a and b are parameters; t1 is the start time of rapid growth of the branch; t2 is the end time of rapid growth of the branch; 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; The scatter plot of fruit quality indexes was drawn, and single factor analysis was performed on it. Pearson's method was used for correlation analysis, and the difference between the mean values ​​was evaluated using LSD test (P<0.05). The full flowering period was defined as the 0th day of fruit development and growth. The number of days after full flowering was x, and the fruit index was 'y. The growth rate equation corresponding to each fruit index was obtained by online derivation. The inflection point prediction used -b / 2a (applicable to quadratic equations) and the second-order derivative f″(x)=0 (applicable to cubic equations); Step 5: construct the growth model of new shoot length and thickness under different branch pulling angles, and use equation (1) to fit the growth data of new shoot length and thickness 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), and (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), and the late growth stage (t2, t n ) three stages; Step 7, evaluate the changes in the growth rate of new shoot length and thickness under different branch pulling angles, and determine whether there are significant differences between different test groups at each growth stage; Step 8: constructing a mathematical equation model of fruit growth under 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, and compare whether there are significant differences between different test groups of various fruit indicators.

2. The method for evaluating the branch pulling of trellis pear trees based on the 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 between the arms of each tree and the central trunk, 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, which are 60°, 30°, and 0° respectively.

3. The method for evaluating the 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 the 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 using the area formula.

4. The method for evaluating the branch pulling of trellis pear trees based on a growth model according to claim 1, characterized in that: In step three, pick Cuiguan fruits without obvious mechanical damage and pests and diseases according to the test groups, weigh the fruit weight with an electronic balance, measure the longitudinal and transverse diameters of the fruit with a vernier caliper, and calculate the fruit shape index, which is the maximum longitudinal diameter / maximum transverse diameter. The fruit hardness is measured by a fruit hardness meter at the part with the largest transverse diameter of the fruit, and each group is measured 3 times, and the results are averaged. The soluble solids content is measured with a sugar meter; the titratable acid content is measured with an acidometer, and each sample is measured 3 times, and the average value is taken.

5. The method for evaluating the branch pulling of trellis pear trees based on a growth model according to claim 1, characterized in that: In step 4, the k value is determined according to the three-point rule, and the observation values ​​(t a ,y a )、(t b ,y b ) and (t c ,y c ),make:

6. A method for evaluating the pulling of branches of trellis pear trees based on a growth model according to claim 1 or 5, characterized in that: In step 4, the duration of rapid growth is T (T = t2-t1), and the initial growth period is Rapid growth period Late growth According to the k value and the y value, a series of y' values ​​corresponding to different time points are obtained, and then the linear regression equation is fitted with time as the horizontal axis and y' as the vertical axis, and R is obtained. 2 value.

7. The method for evaluating the 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, namely, transverse diameter, sugar content, hardness, weight and longitudinal diameter, during the growth process of the fruit in each experimental group were analyzed. 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 the corresponding fitting models were constructed.

8. A method for evaluating the pulling of branches of trellis pear trees based on a growth model according to claim 1 or 7, characterized in that: In step eight, curves are drawn at the time points of 78d, 87d, 100d, 112d, 119d and 127d after full flowering.

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