Cotton boll water flux balance equation and phloem hydraulic conductivity quantification method

Abstract

The invention discloses a cotton boll water flux balance equation and a phloem hydraulic conductivity quantification method, and relates to the technical field of plant physiology and agricultural engineering. The method comprises the following steps: measuring the water vapor diffusion conductance of the fruit surface and the hydraulic conductance of the fruit xylem, monitoring the fresh weight and dry weight change of the fruit and the daily change of the water potential of the fruit and the stem, establishing a water flux balance equation of entering and exiting the fruit, and calculating the hydraulic conductance of the phloem. Parameters such as related conductance and osmotic potential are calculated through a formula, the phloem water flux is calculated according to a fruit phloem sugar unloading path selection formula, and then the phloem hydraulic conductance is obtained. The method solves the problem that a systematic quantification method for phloem hydraulic conductivity is lacked in the prior art, can accurately track the moisture flux of the fruits, provides a basis for crop stress-resistant variety breeding and accurate irrigation, and is suitable for fruit crops such as cotton and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of plant physiology and agricultural engineering technology, and particularly relates to a cotton boll water flux balance equation and a phloem water conductivity quantification method. BACKGROUND

[0002] As the core organ of cotton yield and quality formation, the water transport mechanism of cotton bolls directly affects fiber development. Studies have shown that the xylem of cotton bolls is not mature during the early development stage, and more than 80% of the water is transported by the phloem, so the dynamic water conductivity of the phloem sieve-tube-companion cell complex directly determines the cotton boll swelling rate and dry matter accumulation efficiency. However, the existing research has some deficiencies: on the one hand, traditional plant water physiology focuses on the xylem vessel system, and lacks a quantification method for phloem water conductivity, which makes it impossible to analyze the quantitative relationship between water input flux and cotton boll growth parameters; on the other hand, the existing method relies on indirect calculation of phloem water conductivity (such as pressure probe technology), which ignores the coupling effect of phloem osmotic pressure and pressure flow and the dynamic influence of cotton boll surface transpiration, seriously restricting the selection of stress-resistant varieties and the optimization of precise irrigation strategies. The present technology solves the above scientific problems: by constructing a “cotton boll water flux balance equation”, the water input of phloem and xylem and the cotton boll surface transpiration are included in a unified calculation framework, and combined with the dynamic monitoring results of linear displacement sensors, the precise tracking of cotton boll water flux is realized.

[0003] On the basis of the existing research, the present application establishes a method for quantifying the phloem water conductivity of cotton fruits, which can calculate the specific values of the phloem water conductivity of cotton fruits at different development stages. SUMMARY

[0004] The present application provides a method for dynamically and accurately quantifying the phloem water conductivity of fruits, which solves the technical gap of the prior art in lacking a quantification method for phloem water conductivity and serves the research on efficient water use of crops.

[0005] To solve the above problems, the present application provides a cotton boll water flux balance equation and a phloem water conductivity quantification method, which comprises the following steps: S1, measuring the fruit surface water vapor diffusion conductivity; S2, measuring the fruit xylem water conductivity; S3, monitoring the changes of fruit fresh weight and dry weight; S4, measuring the daily changes of fruit and stem water potential; S5, establishing a fruit in-out water balance equation and calculating the phloem water conductivity.

[0006] 2. The fruit in-out water balance equation and phloem water conductivity quantification method according to claim 1, wherein the step of measuring the fruit surface water vapor diffusion conductivity comprises: Sample at 7:00-8:00 in the morning, seal the fruits for transportation to the laboratory, measure the transverse diameter, longitudinal diameter and initial fresh weight, seal the incision with hot melt adhesive, calculate the weight loss rate by timed weighing, combine with the environmental temperature and humidity, and calculate the water vapor diffusion conductivity using the following formula: rho = -K1 / 1000 * R * (273.15 + T) / (18 * VPD) ; Where rho (cm h -1 ), K1 (g cm -2 h -1 ), T (℃) and VPD (KPa) are the water vapor diffusion conductivity of the boll surface, the weight loss rate per unit area of the boll, the temperature of the environment and the water vapor pressure difference on the boll surface, respectively; R is the gas constant, with a value of 83.14, cm 3 bar -1 mol -1 K -1 .

[0007] Further, the step of measuring the hydraulic conductivity of the fruit xylem includes: Sample at 7:00-8:00 in the morning, the fruit stem length is required to be 3-5 cm, seal the fruits for transportation to the laboratory, use a plant pressure chamber to complete the measurement of the initial water potential of the fruit within 2-3 min, measure the transverse and longitudinal dimensions of the fruit with a vernier caliper, and weigh the fresh weight of the fruit and stem with an analytical balance, conduct a water absorption test under 100% environmental humidity, monitor the weight change and water potential during the water absorption process of the fruit, and calculate the hydraulic conductivity of the fruit xylem using the following formula: L pcf = -ΔW / (A * Ψ f * Δt) Where Ψ f is the fruit water potential (bar), A is the fruit surface area (cm²), ΔW / Δt is the fruit weight change rate (gmin -1 ), L pcf is the hydraulic conductivity of the fruit xylem, cm 3 min -1 bar -1 cm -2 .

[0008] Further, the step of monitoring the changes in fresh weight and dry weight of the fruit includes: The linear displacement sensor is used to monitor the change in fruit transverse diameter ΔD in situ, and the water content change ΔW is calculated based on the transverse diameter-volume relationship, fruit density and water content.

[0009] Further, the step of measuring the daily changes in fruit and stem water potential includes: On the same day of monitoring the change of fruit transverse diameter, the water potential of fruit and stem was measured by using plant pressure chamber at 5:00, 8:00, 11:00, 14:00, 17:00, 20:00, 23:00, 2:00 time points, and the fruit solute concentration C was determined by using osmometer f .

[0010] Further, the fruit water flux balance equation is: ΔW = Q x +Q ph -Q tr Q x = (Ψ x - Ψ f )*L pcf *A Ψ x = Ψ ph = Ψ stem wherein Q x is the water flux entering the cotton boll through xylem, cm 3 min -1 ; Q ph is the water flux entering the cotton boll through phloem, cm 3 min -1 ; Q tr is the water flux of water vapor evaporation on the surface of cotton boll, cm 3 min -1 ; Ψ x is the water potential of xylem of stem, MPa; Ψ f is the water potential of cotton boll, MPa; Ψ ph is the water potential of phloem of stem, MPa; and Ψ stem is the water potential of stem, MPa.

[0011] Further, the calculation of the water flux Q ph entering the cotton boll through phloem is according to the pathway selection formula of sugar unloading into the cotton boll: Symplasmic pathway: Q ph = ( P ph -P f ) *L ph *A wherein Pph P is the stem phloem turgor pressure, MPa; L f P is the cotton boll fruit turgor pressure, MPa; L ph L is the phloem hydraulic conductance; apoplast pathway: Q ph = ( Ψ ph - Ψ f ) *L ph *A Ψ ph is the stem phloem water potential, Ψ f is the cotton boll fruit water potential.

[0012] Further, the calculation formula of the stem phloem water potential Ψ ph and the fruit water potential Ψ f is: Ψ ph =P ph +π ph Ψ f =P f +π f wherein, π ph and π f are the phloem and fruit osmotic potential, respectively, calculated by the following formula: π ph = -iRTC / σ ph = -iRTC π f = (β * ΔDW / η + r * DW * t * β / η) / N / (ΔW / 1000) f π ph and π f are the phloem and fruit osmotic potential, MPa; i is the dissociation coefficient, equal to 1 when the solute is mainly sucrose; R is the gas constant, taking the value of 0.0083 L MPa -1 mol -1 K -1 ; C ph and C f are the phloem sugar concentration and cotton boll solute concentration, respectively, mol L -1; T is the temperature in Kelvin, (273+t℃) ; sigma is the contribution of sucrose in phloem sap to the osmotic potential.

[0013] Further, the fruit includes a cotton fruit, and the phloem sugar concentration C ph By the formula: C ph r = m + ((1 - Y ) * (1 / DW) * (d , wherein beta=1.764g is the amount of glucose required for 1g of cotton boll dry matter to be produced, eta=1.053g is the amount of glucose required for 1g of sucrose to be produced, and N=342.3g mol -1 is the molecular weight of sucrose; r is the cotton boll respiration rate, g of respiratory substrate / g of dry matter / day; DW is the cotton boll dry weight, g; and t is the cotton boll respiration time, d.

[0014] Further, the cotton boll respiration rate r is calculated by the formula Figure 1 G ) / Y G Figure 2 DW / d t ) , wherein r is the respiration rate in g of respiratory substrate / g of dry matter / day; m is the maintenance respiration rate, g of respiratory substrate / g of dry matter / day, and is taken as 0.006±0.01; Y G is the efficiency of substrate conversion into cotton boll dry matter (excluding maintenance respiration), g of dry matter / g of substrate, and is taken as 0.74±0.01.

[0015] Compared with the prior art, the present application has the following beneficial effects: 1. Filling the technical blank, establishing a systematic quantitative method; The prior art has long relied on indirect calculation or single parameter estimation for the study of phloem hydraulic conductivity, and lacks a dynamic balance model that comprehensively considers the phloem, phloem, fruit surface transpiration and respiration. The present application first proposes a phloem hydraulic conductivity quantification method based on the fruit in-out water flux balance equation, integrates multi-dimensional data such as fruit surface water vapor diffusion conductivity, fruit xylem hydraulic conductivity, water potential daily variation and dry matter accumulation, and constructs a complete calculation framework, solving the problem of lack of systematic method for phloem hydraulic conductivity quantification in the prior art.

[0016] 2. Realize dynamic and accurate monitoring; The traditional method (such as pressure probe technology) only calculates the phloem water transport through static measurement, ignoring the dynamic changes in the fruit development process. The linear displacement sensor is used to monitor the transverse diameter change of the fruit in situ, and the precise water potential instrument (such as plant pressure chamber) and timed weighing technology are combined to realize the real-time dynamic tracking of fruit water flux, which significantly improves the accuracy and reliability of the data.

[0017] 3. Strong universality; The present application provides differentiated calculation formulas for different ways of sugar unloading into cotton bolls (symplast and apoplast): Symplast pathway: based on the difference between the stem phloem and the fruit turgor pressure (P) P ph -P f driving water transport; Apoplast pathway: based on the difference between the stem phloem and the fruit water potential (P) Figure 3 ph Figure 4 f driving water transport.

[0018] This method can be flexibly applied to different crops or growth stages, expanding the application range of the technology.

[0019] 4. High application value; The existing technology cannot directly quantify the phloem hydraulic conductivity, making it difficult to analyze the quantitative relationship between water input and fruit growth. The present application accurately calculates the phloem hydraulic conductivity of the fruit, which can clearly determine the correlation between water transport efficiency and fruit enlargement and dry matter accumulation, providing scientific basis for breeding of stress-resistant varieties (such as drought-resistant and salt-tolerant) and precise irrigation strategies (such as optimizing irrigation time and water quantity), and helping agricultural water-saving and yield increase.

[0020] 5. Standardized and repeatable operation, easy to popularize and apply; Compared with the traditional method with ambiguous experimental process (such as non-uniform sampling time and non-standardized environmental conditions), the present application clearly defines the technical details of the key steps, for example: The sampling time is specified as 7:00-8:00 am to reduce transpiration interference; 100% humidity environment is used for fruit xylem hydraulic conductivity measurement to eliminate errors; Combined with linear displacement sensor and drying method to monitor the changes of fruit fresh weight and dry weight. These standardized operations ensure the stability and repeatability of experimental results, and are easy to popularize in laboratory and field.

[0021] In summary, the present application realizes dynamic and accurate quantification of phloem hydraulic conductivity by innovatively constructing a fruit in-out water balance equation, which not only overcomes the limitations of the prior art, but also provides an efficient and reliable technical means for plant water physiology research and agricultural production practice. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 5 Fig. 1 is a schematic diagram of a linear displacement sensor monitoring fruit transverse diameter change in the present application; Figure 6 Fig. 2 is a fitting curve of fruit transverse diameter and volume in the present application; Figure 7 Fig. 3 is a curve of fruit density change with growth period in the present application; Figure 8 Fig. 4 is a curve of fruit water content change with growth period in the present application; rho = -K1 / 1000 * R * (273.15 + T) / (18 * VPD) Fig. 5 is a schematic diagram of establishing a cotton boll water flux balance equation and quantifying phloem hydraulic conductivity in 1 day in the present application; = -ΔW / (A * Ψ Fig. 6 is data of cotton boll and stem water potential daily change after 25 days of flowering in the present application; * Δt) Fig. 7 is data of cotton boll solute concentration daily change after 25 days of flowering in the present application; Figure 1 Fig. 8 is a calculation process of cotton boll phloem hydraulic conductivity within 25 days after flowering in the present application. DETAILED DESCRIPTION

[0023] In order to make the technical solutions of the present application clearer and more concise, the present application will be described more clearly and completely below in combination with examples. Obviously, the examples mentioned below are only examples of the present application. Without creativity, the remaining examples obtained by workers in the art based on the examples of the present application all belong to the scope of protection of the present application.

[0024] Example: A cotton boll water flux balance equation and phloem hydraulic conductivity quantification method is provided Step one: sample measurement of cotton fruit surface water vapor diffusion conductivity Sampling was done between 7:00 and 8:00 am, and the fruits were cut from the plant and placed in a ziplock bag, sealed, and immediately transported to the laboratory in an insulated box with ice packs (to prevent transpiration). The peduncle was removed, and the fruit was measured for cross diameter (D1, D2) and longitudinal diameter (D3) using a vernier caliper. The fruit was then sealed with a hot glue gun. The cotton boll was then placed on a test tube rack and fanned to ensure that the only resistance to water loss from the surface of the cotton boll was the cuticle. The weight of the cotton boll was then measured every hour for eight hours, and the temperature and humidity of the environment were recorded simultaneously. From these measurements, the surface area (A), volume (V), overall rate of weight loss (K), and rate of weight loss per unit area (K1) of the cotton boll were calculated. Further, the water vapor diffusion conductance (rho) of the cotton boll surface was calculated using the following equation: Figure 2 where rho (cm h -1 ), K1 (g cm -2 h -1 ), T (°C), and VPD (KPa) are the water vapor diffusion conductance of the cotton boll surface, the rate of weight loss per unit area of the cotton boll, the temperature of the environment, and the water vapor pressure difference across the surface of the cotton boll, respectively; R is the gas constant, taken as 83.14, cm 3 bar -1 mol -1 K -1 . The surface area and volume of the cotton boll were calculated assuming the cotton boll to be an ellipsoid.

[0025] Step two: Sampling and measuring the hydraulic conductance of the xylem of the cotton fruit First, fruits with 3-5 cm peduncles were cut from the plant between 7:00 and 8:00 am and immediately placed in a ziplock bag with a wet paper towel to seal. They were then placed in an insulated box with ice packs to slow transpiration. Within ten minutes, the samples were transported to the laboratory, and the initial water potential (Ψ f0 ) of the fruit was measured using a portable plant water potential chamber within 2-3 min. The cross and longitudinal diameters of the fruit were then measured using a vernier caliper, and the fresh weight of the fruit and peduncle was measured using an analytical balance. Next, a water uptake experiment was performed.

[0026] The fruit water absorption test device consists of two parts: one part is to ensure 100% relative humidity, including a humidifier, a temperature and humidity sensor, a plastic box with a lid, a storage rack, a towel and a wet paper; the other part is the device for fruit water absorption, including a centrifuge tube containing deionized water treated by ultrasonic degassing. Before the experiment, the relative humidity of the water absorption device is adjusted to 100%. Use raw material tape to wrap around the fruit stem, and use a self-sealing bag to wrap the fruit surface, to ensure that the fruit only absorbs water through the fruit stem cut surface. In the deionized water, quickly trim the fruit stem with a blade, wipe off the water immediately after trimming with a water absorption paper, and weigh with an analytical balance, then quickly connect to the water absorption device. Thereafter, every hour, take out the fruit, wipe off the water with a water absorption paper, weigh, and measure the fruit water potential. The whole test is carried out in a constant temperature environment of 25℃.

[0027] During the water absorption process of cotton bolls, the increase in fresh weight of cotton bolls is equal to the amount of water absorbed. Therefore, the hydraulic conductivity (L pcf ) of the fruit xylem can be calculated according to the following formula: L pcf Figure 3 f Figure 4 where Ψ f is the fruit water potential (bar), A is the fruit surface area (cm²), ΔW / Δt is the fruit weight change rate (gmin -1 ), L pcf is the fruit xylem hydraulic conductivity, cm 3 min -1 bar -1 cm -2 .

[0028] Step three: calculate the fresh weight and dry weight change of cotton bolls in one day (1) Measure the initial transverse diameter (D0) of the cotton boll with a vernier caliper between 8:00 and 9:00 in the morning, then monitor the change in fruit transverse diameter ΔD in situ using a linear displacement sensor, as shown in Figure 3 .

[0029] (2) After taking off the cotton bolls at different growth stages, put them into an incubator and transport them to the laboratory, measure the fruit transverse and longitudinal diameters and fresh weight with a vernier caliper, then put them into an oven at 85℃ to dry to obtain the moisture content of the cotton bolls, thereby establishing the correlation between the transverse diameter of the cotton bolls and the fruit volume (as shown in Figure 7 ), the density change at different growth stages (as shown in ΔW = Q ), and the change of cotton boll moisture content with growth stage (as shown in = (Ψ ).

[0030] (3) According to the change of boll diameter monitored by linear displacement sensor, the boll diameter D at the end of monitoring can be obtained. According to the relationship between boll diameter and volume, the boll volume V can be calculated. Assuming that the boll density and water content are constant within 1 day, the change of boll water content ΔW within 1 day can be calculated by - Ψ The boll density changes non-linearly with the growth period at different growth periods, so the change of boll water content ΔW within 1 day can be calculated.

[0031] Step four: Measurement of daily changes of boll water potential and osmotic potential and stem water potential On the same day when the linear displacement sensor is used to monitor the change of boll diameter, the daily changes of boll and stem water potential are measured by using plant pressure chamber, and the sampling time is 5:00, 8:00, 11:00, 14:00, 17:00, 20:00, 23:00 and 2:00. After the water potential is measured, the bolls are quickly frozen in liquid nitrogen and stored in a-80℃ refrigerator, and the boll solute concentration C f changes daily (as shown in Ψ ).

[0032] Step five: Establishment of boll water flux balance equation within 1 day and quantification of phloem hydraulic conductivity It is assumed that the change of boll weight is mainly due to the accumulation of water and solute. In addition, it is assumed that the water in the boll mainly comes from the transportation of xylem and phloem, and the water loss mainly comes from the diffusion of water vapor on the surface of the boll and the backflow of xylem.

[0033] (1) Assuming that the water transport in xylem is mainly driven by the difference between stem and fruit water potential, the xylem water potential is equal to the stem phloem water potential, and the stem phloem water potential is equal to the stem water potential, the boll water flux balance equation within 1 day can be established: = Ψ x +Q ph -Q tr Q x = Ψ x Figure 5 f )*L pcf *A = (Ψ x - Ψ ph Ψ stem where Q x is the water flux into the boll through xylem, cm 3 min -1 ; Q phcm 3 min -1 ; Q tr cm 3 min -1 ; Ψ x MPa; Ψ f MPa; Ψ ph MPa; Ψ stem MPa.

[0034] (2) Quantification of phloem conductance into bolls within 1 day, as shown in Ψ Previous studies have shown that there are two pathways for phloem unloading into bolls, symplastic (0-9 days after anthesis and after 16 days after anthesis) and apoplastic (10-15 days after anthesis). If phloem unloading into bolls is through the symplastic pathway, it is mainly driven by the difference in turgor pressure between stem phloem and fruit; conversely, if phloem unloading into bolls is through the apoplastic pathway, it is mainly driven by the difference in water potential between stem and fruit: Q ph =（P ph -P f ）*L ph *A Symplastic pathway Q ph = -iRTC / σ ph = -iRTC f ）*L ph *A Apoplastic pathway = (β * ΔDW / η + r * DW * t * β / η) / N / (ΔW / 1000) ph =P ph +π ph Fruit Repetition f =P f +π f π ph Initial Fruit Transverse Diameter (mm) ph Change in Fruit Transverse Diameter in 1 Day (mm) π f Cotton Boll Water Content (g / g FW) f Figure 6 G ) / Y G Figure 8 DW / d t ) C ph ​ where P ph is the stem phloem turgor pressure, MPa; P f is the boll turgor pressure, MPa; L ph is the phloem hydraulic conductance, cm 3 min -1 bar -1 cm -2 ; p ph and p f are the stem phloem and fruit osmotic potential, MPa; i is the dissociation coefficient, which is assumed to be 1 if the solute is mainly sucrose; R is the gas constant, which is assumed to be 0.0083 L MPa -1 mol -1 K -1 ; C ph and C f are the phloem sugar concentration and boll solute concentration, mol L -1 ; s is the contribution of sucrose to the osmotic potential in the phloem sap, which is assumed to be 0.70 because the soluble sugar content in the phloem sap is more than 70% of the metabolites, and sucrose is the main component of the soluble sugar; r is the boll respiration rate, g respiratory substrate / g dry matter / day; m is the maintenance respiration rate, g respiratory substrate / g dry matter / day, which is assumed to be 0.006 ± 0.01; Y G is the efficiency of substrate conversion to dry matter (excluding maintenance respiration), g dry matter / g substrate, which is assumed to be 0.74 ± 0.01; T is the temperature in Kelvin, (273 + t°C); b is the amount of glucose needed to produce 1 g of boll dry matter, which is assumed to be 1.764 g, without considering the growth and maintenance respiration consumption; n is the amount of glucose needed to produce 1 g of sucrose, which is assumed to be 1.053 g; DW is the boll dry weight, g; t is the boll respiration time, d; N is the molecular weight of sucrose, 342.3 g mol -1 .

[0035] Table 1 Linear displacement sensor data ​ ​ ​ ​ 1 29.52 0.24 0.81 2 26.65 0.32 0.81 3 26.25 0.14 0.81 4 31.24 0.21 0.81 5 30.41 0.26 0.81 6 29.81 0.27 0.81 (3) Taking the calculation of the phloem hydraulic conductance of the boll within 25 days after flowering as an example: the linear displacement sensor data is shown in Table 1, the boll water potential and the stem water potential are shown in​ The calculation process of hydraulic conductance of cotton phloem in 1 day is shown in ​ .

[0036] The above examples only represent some preferred cases, and the application is not limited to the above examples. Those skilled in the art can still modify or equivalently replace the technical solutions listed in the application, and any modification, equivalent replacement or improvement made within the spirit and principle of the application is protected by the application.

Claims

1. A method for quantifying the water flux balance equation and phloem hydraulic conductivity of cotton bolls, characterized in that, Includes the following steps: S1. Measure the water vapor diffusion conductance on the fruit surface; S2. Measure the hydraulic conductivity of the xylem of the fruit; S3. Monitor changes in fruit fresh weight and dry weight; S4. Measure the daily changes in water potential of fruits and stems; S5. Establish the water flux balance equation for the fruit and calculate the hydraulic conductivity of the phloem.

2. The method for quantifying the water flux balance equation and phloem hydraulic conductivity of cotton bolls according to claim 1, characterized in that, The steps for measuring the water vapor diffusion conductance on the fruit surface include: Samples were taken between 7:00 and 8:00 AM, and the fruits were transported to the laboratory in sealed containers. The transverse diameter, longitudinal diameter, and initial fresh weight were measured. The rate of weight loss was calculated by weighing the fruits at regular intervals. Combined with the ambient temperature and humidity, the water vapor diffusion conductance on the fruit surface was calculated using the following formula: rho=-K1 / 1000*R*(273.15+T) / (18*VPD) ； Among them, rho (cm h) -1 K1 (g cm) -2 h -1 T (°C), VPD (kPa) represent the water vapor diffusion conductance at the cotton boll surface, the rate of weight loss per unit area of ​​the cotton boll, the ambient temperature, and the water vapor pressure difference at the cotton boll surface, respectively; R is the gas constant, with a value of 83.14 cm⁻¹. 3 bar -1 mol -1 K -1 .

3. The method for quantifying the water flux balance equation and phloem hydraulic conductivity of cotton bolls according to claim 1, characterized in that, The steps for measuring the hydraulic conductivity of the fruit xylem include: Sampling was conducted between 7:00 and 8:00 AM. After sampling, the fruit stalks were trimmed to 3-5 cm, and the fruits were sealed and transported to the laboratory. The initial water potential of the fruit was measured within 2-3 minutes using a plant pressure chamber. The transverse and longitudinal diameters of the fruit were measured with vernier calipers, and the fresh weight of the fruit and stalks was weighed using an analytical balance. A water absorption test was conducted under 100% ambient humidity. The weight and water potential changes of the fruit during the water absorption process were monitored regularly. The hydraulic conductivity of the xylem of the fruit was calculated using the following formula: L pcf =-ΔW / (A*Ψ f *Δt) Among them, Ψ f Let A be the water potential of the fruit (bar), A be the surface area of ​​the fruit (cm²), and ΔW / Δt be the rate of change of fruit weight (g / min). -1 ), L pcf For the hydraulic conductivity of the xylem of the fruit, cm 3 min -1 bar -1 cm -2 .

4. The method for quantifying the water flux balance equation and phloem hydraulic conductivity of cotton bolls according to claim 1, characterized in that, The steps for monitoring changes in fruit fresh weight and dry weight include: The change in fruit transverse diameter ΔD was monitored in situ using a linear displacement sensor. Combined with the transverse diameter-volume relationship, fruit density, and water content, the change in fruit moisture content ΔW within one day was calculated.

5. The method for quantifying the water flux balance equation and phloem hydraulic conductivity of cotton bolls according to claim 1, characterized in that, The steps for measuring the daily changes in water potential of fruits and stems include: On the same day that the changes in fruit transverse diameter were monitored, the water potential of the fruit and stem was measured using a plant pressure chamber at 5:00, 8:00, 11:00, 14:00, 17:00, 20:00, 23:00, and 2:00, and the solute concentration C of the fruit was determined using an osmotic potential meter. f .

6. The method for quantifying the water flux balance equation and phloem hydraulic conductivity of cotton bolls according to claim 1, characterized in that, The water flux balance equation for the fruit is as follows: ΔW=Q x +Q ph -Q tr Q x =(Ψ x -Ψ f )*L pcf *A Ψ x =Ψ ph =Ψ stem Q x For the water flux entering the cotton boll through the xylem, cm 3 min -1 Q ph To determine the water flux entering the cotton boll through the phloem, cm 3 min -1 Q tr The evaporation flux of water vapor on the surface of the cotton boll, in cm 3 min -1 Ψ x Water potential of the xylem in the stem, MPa; Ψ f The water potential of the cotton boll is expressed in MPa; Ψ ph The water potential of the stem phloem is expressed in MPa; Ψ stem The stem water potential is expressed in MPa.

7. The method for quantifying the water flux balance equation and phloem hydraulic conductivity of cotton bolls according to claim 6, characterized in that, The water flux Q entering the cotton boll through the phloem ph The calculation is based on the formula for selecting the pathway of sugar unloading into the cotton boll: Symplast pathway: Q ph =（P ph -P f ）*L ph *A , where P ph The turgor pressure of the stem phloem is MPa; P f The turgor pressure of cotton bolls, MPa; L ph Hydraulic conductivity of the phloem; Apoplast pathway: Q ph =(Ψ ph -Ψ f ）*L ph *A Ψ ph For the water potential of the stem phloem, Ψ f The water potential of cotton bolls.

8. The method for quantifying the water flux balance equation and phloem hydraulic conductivity of cotton bolls according to claim 7, characterized in that, The stem phloem water potential Ψ ph and fruit water potential Ψ f The calculation formula is: Ψ ph =P ph +π ph Ψ f =P f +π f in, π ph and π f The osmotic potentials of the phloem and fruit are respectively calculated using the following formula: π ph =-iRTC ph / σ π f =-iRTC f π ph and π f ρ represents the osmotic potential of the phloem and fruit, in MPa; i is the dissociation coefficient, which equals 1 when the solute is mainly sucrose; R is the gas constant, with a value of 0.0083 L MPa. -1 mol -1 K -1 C ph and C f These represent the sugar concentration in the phloem and the solute concentration in the cotton boll, respectively, in mol / L. -1 T is the Kelvin temperature (273+t℃); σ is the percentage of sucrose contribution to the osmotic potential in the phloem sap.

9. The method for quantifying the water flux balance equation and phloem hydraulic conductivity of cotton bolls according to claim 1, characterized in that, phloem sugar concentration C ph Through the formula: C ph =(β*ΔDW / η+r*DW*t*β / η) / N / (ΔW / 1000) Calculate the amount of glucose required to produce from 1g of dry cotton boll matter, where β = 1.764g is the amount of glucose required to produce from 1g of sucrose, η = 1.053g is the amount of glucose required to produce from 1g of sucrose, and N = 342.3g mol. -1 is the molecular weight of sucrose; r is the cotton boll respiration rate, g respiration substrate / g dry matter / day; DW is the cotton boll dry weight, g. t represents the respiration time of the cotton boll, d.

10. The method for quantifying the water flux balance equation and phloem hydraulic conductivity of cotton bolls according to claim 9, characterized in that, The cotton boll respiration rate r is expressed by the formula: r=m+((1-Y G ) / Y G )*(1 / DW)*(dDW / dt) Calculate r, where r is in g respiratory substrate / g dry matter / day; m is the maintenance respiratory rate, in g respiratory substrate / g dry matter / day, with a value of 0.006±0.01; Y G The efficiency of substrate conversion into cotton boll dry matter is expressed as g dry matter / g substrate, with a value of 0.74 ± 0.01.

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