A plant stem flow measurement device and a method for measuring the stem flow of hollow-stem plants

Abstract

The present invention discloses a plant stem flow measuring device and a method for measuring the stem flow of hollow-stemmed plants, belonging to the technical field of plant stem flow meters. The device includes a probe adjusting frame equipped with a plant stem flow meter. The probe adjusting frame includes a first positioning guide rail, a second positioning guide rail, an adjusting mounting plate, and an adjusting mechanism. The ends of the first positioning guide rail and the second positioning guide rail are respectively provided with a first positioning port and a second positioning port. The heating probe and the reference probe of the plant stem flow meter are fixed on the adjusting mounting plate, and there is a safety distance between the heating probe and the reference probe. The method includes: S1, measuring the wall thickness of the hollow stem; S2, drilling heating pinholes and reference pinholes arranged vertically on the stem epidermis; S3, buckling the first positioning port and the second positioning port on the stem, and inserting the heating probe and the reference probe into the heating pinholes and the reference pinholes at a preset penetration depth; S4, continuously heating the heating probe, measuring the temperature difference, and calculating the stem flow velocity. The penetration depth is flexibly controlled to ensure the penetration perpendicularity.

Description

Technical Field

[0001] The present invention relates to the technical field of plant sap flow meters, and particularly to a plant sap flow measuring device and a method for measuring the sap flow of hollow-stem plants. Background Art

[0002] The plant sap flow process is closely related to its physiological process. After the liquid water in the soil enters the root hairs and is transported upward through the stem, most of the water is converted into gaseous water through plant transpiration and diffused into the atmosphere, and only a very small amount of water is used for its own metabolic process. Therefore, it is generally considered that the water consumption of plant transpiration is roughly equal to the amount of water absorbed by the plant from the soil, that is, the transpiration water consumption of the plant is equivalent to the sap flow rate measured at the plant stem.

[0003] At present, the measurement methods of plant stem sap flow mainly adopt thermal technologies mainly based on heat pulse, heat diffusion and stem heat balance, which have the advantages of not being limited by terrain and spatial heterogeneity and being able to accurately measure the plant sap flow rate. Among them, the heat diffusion probe method is the current mainstream measurement method. By radially inserting the heating probe and the reference probe of the plant sap flow meter up and down into the plant stem, the upper heating probe continuously passes through an electric current to heat, and the lower reference probe is not heated. The temperature difference between the two probes is the only variable in this measurement method. By substituting the temperature difference between the two probes into the Granier empirical equation, the sap flow velocity can be deduced. This method has relatively low cost, and the construction and installation of the sensor are relatively easy. However, at present, the penetration depth of the probe of the plant sap flow meter is completely controlled by hand, and there is no reference for the penetration depth, which is difficult to meet the measurement requirements for the penetration depth or plants that have requirements for the penetration depth itself. For plants with requirements for the penetration depth, such as hollow plants, especially bamboo plants, because bamboo plants are hollow and the bamboo wall is relatively thin, usually about 10-15 cm, while the probe is usually 20 cm long. When inserting, there is no reference, and it is very easy to pierce through the bamboo wall and extend into the bamboo cavity if the penetration depth is not well controlled. The bamboo cavity has a heat storage effect, which will increase the temperature of the bamboo wall around the heating probe, resulting in measurement errors. And by shortening the length of the existing plant sap flow meter probe to avoid this problem, this measuring instrument cannot be applied to the measurement of other plants. In addition, since the probe is usually directly inserted into the plant stem by hand, it is difficult to ensure the perpendicularity of the probe. Summary of the Invention

[0004] The object of the present invention is to solve the above technical problems, and provide a plant sap flow measuring device and a method for measuring the sap flow of hollow-stem plants. By controlling the position of the adjustment mounting plate on the first positioning guide rail and the second positioning guide rail through the adjustment mechanism, the penetration depth of the probe can be controlled, so as to cope with the measurement requirements for the measurement depth or the plants with requirements for the penetration depth. At the same time, through the positioning of the first positioning port and the second positioning port and the guidance of the first positioning guide rail and the second positioning guide rail, the perpendicularity of the probe penetration can be ensured. In addition, when not in use, by retracting the adjustment mounting plate, the probe can be received between the first positioning guide rail and the second positioning guide rail to protect the probe.

[0005] To achieve the above object, the present invention provides the following solutions: The present invention discloses a plant sap flow measuring device, which is characterized in that it includes a probe adjustment frame installed with a plant sap flow meter. The probe adjustment frame includes a first positioning guide rail, a second positioning guide rail, an adjustment mounting plate and an adjustment mechanism. The first positioning guide rail and the second positioning guide rail are arranged at intervals and are parallel to each other. The ends of the first positioning guide rail and the second positioning guide rail are respectively provided with a first positioning port and a second positioning port for coaxially buckling on the plant stem. The two ends of the adjustment mounting plate are respectively slidably connected to the first positioning guide rail and the second positioning guide rail. The adjustment mechanism includes a driving component for controlling the moving distance of the adjustment mounting plate. The heating probe and the reference probe of the plant sap flow meter are both fixed on the plate surface of the adjustment mounting plate facing the first positioning port. The heating probe and the reference probe are located on the central connection line between the first positioning port and the second positioning port. The heating probe and the reference probe are respectively close to the first positioning guide rail and the second positioning guide rail. There is a safety distance between the heating probe and the reference probe to ensure that the two do not interfere with each other. The axes of the heating probe and the reference probe are both parallel to the first positioning guide rail.

[0006] Preferably, both the first positioning guide rail and the second positioning guide rail are U-shaped guide rails. Linear sliding grooves are provided on the opposite surfaces of the U-shaped guide rails. The adjustment mounting plate is slidably connected to the linear sliding grooves through adjustment sliders.

[0007] Preferably, the adjustment mechanism includes an adjustment knob, an adjustment gear and an adjustment rack fixed on the adjustment slider. The adjustment knob is rotatably connected to the outer wall of the U-shaped guide rail. A gear installation groove communicating with the linear sliding groove close to the adjustment knob is provided on the U-shaped guide rail. The adjustment gear is rotatably connected in the gear installation groove and meshes with the adjustment rack. The adjustment rack is parallel to the linear sliding groove. The adjustment knob is coaxially and fixedly connected to the adjustment gear. A scale ring coaxial with the adjustment knob is provided on the outer wall of the U-shaped guide rail.

[0008] Preferably, a positioning mechanism is provided on the side wall of the U-shaped guide rail. The positioning mechanism includes a positioning cross plate. A guiding chute parallel to the adjusting mounting plate is provided on the positioning cross plate. Two positioning sliders for forming the first positioning port or the second positioning port are slidably connected in the guiding chute. A threaded deep hole is provided on the surface of the positioning slider that fits the guiding chute. A strip-shaped through hole is provided on the bottom wall of the guiding chute. A tightening screw that passes through the strip-shaped through hole is threadedly connected in the threaded deep hole. One end of the tightening screw that passes through the strip-shaped through hole is fixedly connected with a pressing knob that can press against the positioning cross plate.

[0009] Preferably, the probe adjusting frame includes a mounting base, and the first positioning guide rail, the second positioning guide rail and the plant sap flow meter are fixed on the mounting base.

[0010] Preferably, it includes a protection box with an installation cavity. The mounting base is fixed in the installation cavity. An extension port for the first positioning guide rail and the second positioning guide rail to extend out of the installation cavity and communicate is provided on the outer wall of the protection box.

[0011] Preferably, a storage battery for powering the plant sap flow meter is provided in the installation cavity.

[0012] Preferably, a maintenance port communicating with the installation cavity is provided on the protection box. A maintenance box door is hinged at the maintenance port. An observation window for observing the inside of the installation cavity is provided on the maintenance box door.

[0013] A method for measuring the sap flow of hollow-stemmed plants is also disclosed. The above-mentioned plant sap flow measuring device is adopted, including the following steps:

[0014] S1. Measure the wall thickness of the stem of the hollow-stemmed plant, and preset the penetration depths of the heating probe and the reference probe.

[0015] S2. Drill a heating needle hole and a reference needle hole arranged vertically on the stem epidermis of the hollow-stemmed plant. The connection line of the heating needle hole and the reference needle hole is parallel to the axis of the stem of the hollow-stemmed plant.

[0016] S3. Buckle the first positioning port and the second positioning port on the stem of the hollow-stemmed plant in a vertical arrangement, and align the heating probe and the reference probe with the heating needle hole and the reference needle hole respectively. Drive the adjusting mounting plate to move a distance through the adjusting mechanism, so that the heating probe and the reference probe penetrate into the heating needle hole and the reference needle hole respectively according to the preset penetration depths.

[0017] S4. The heating probe continuously passes an electric current for heating, measures the temperature difference between the heating probe and the reference probe, and calculates the stem flow velocity according to the Granier empirical equation.

[0018] Preferably, in step S1, a reference hollow stem plant consistent with the growth trend of the stem of the measured hollow stem plant is selected, the reference hollow stem plant is truncated, and the wall thickness of the stem of the reference hollow stem plant is measured with a vernier caliper.

[0019] The present invention has achieved the following technical effects compared with the prior art:

[0020] 1. The present invention controls the position of the adjusting mounting plate on the first positioning guide rail and the second positioning guide rail through the adjusting mechanism, and can flexibly control the piercing depth of the probe. When measuring hollow stem plants, such as bamboo plants, the probe can be adjusted according to different stem thicknesses, effectively avoiding piercing the stem wall and resulting in inaccurate measurement; through the positioning of the first positioning port and the second positioning port, it can be ensured that the first positioning guide rail and the second positioning guide rail are perpendicular to the stem, and then under the guidance of the first positioning guide rail and the second positioning guide rail, the perpendicularity of the probe piercing can be ensured; moreover, when not measuring, the adjusting mounting plate is retracted, and the probe is received between the first positioning guide rail and the second positioning guide rail to protect the probe.

[0021] 2. The present invention can accurately adjust the piercing depths of the heating probe and the reference probe through the adjusting knob, the scale ring, the adjusting gear and the adjusting rack fixed on the adjusting slider, so as to achieve precise control.

[0022] 3. The present invention is specially provided with a positioning mechanism to adapt to plant stems of different thicknesses. The two positioning sliders on the positioning mechanism are used to form the first positioning port or the second positioning port, and then by loosening or tightening the pressing knob, that is, adjusting the distance between the two positioning sliders, and then adjusting the opening size of the first positioning port or the second positioning port to adapt to plant stems of different stem diameters.

[0023] 4. The present invention is provided with a protection box, which can be placed vertically when not in use and horizontally when in use. At the same time, when the probe is received between the first positioning guide rail and the second positioning guide rail, it is also received in the protection box, thereby realizing the protection of the probe, avoiding damage to key components, improving the service life of the device, and reducing unnecessary economic losses.

[0024] 5. The stem flow measurement method for hollow stem plants of the present invention can effectively avoid the probe piercing into the hollow marrow of the hollow stem, resulting in inaccurate temperature measurement, and this method can be widely used for the measurement of various hollow stem plants, especially bamboo plants. Description of the Drawings

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0026] Figure 1 It is a schematic structural diagram of a plant stem flow measurement device;

[0027] Figure 2 It is a three-dimensional structural diagram of a probe adjustment frame;

[0028] Figure 3 It is a side view of the probe adjustment frame;

[0029] Figure 4 It is a side-sectional view of the probe adjustment frame;

[0030] Figure 5 It is a three-dimensional structural diagram of a probe adjustment frame provided with a transmission rotating shaft;

[0031] Figure 6 It is a side view of a probe adjustment frame provided with a positioning mechanism;

[0032] Figure 7 It is a top three-dimensional structural diagram of the positioning mechanism;

[0033] Figure 8 It is a bottom three-dimensional structural diagram of the positioning mechanism;

[0034] Figure 9 It is a sectional view of the positioning mechanism.

[0035] Explanation of reference numerals:

[0036] 1. Probe adjustment frame; 2. Plant stem flowmeter; 3. Protection box;

[0037] 101. Installation base; 102. First positioning guide rail; 103. Second positioning guide rail; 104. Adjustment mounting plate; 105. Linear sliding groove; 106. First positioning port; 107. Second positioning port; 108. Adjustment knob; 109. Adjustment gear; 110. Adjustment rack; 111. Gear mounting groove; 112. Scale ring; 113. Positioning cross plate; 114. Guide sliding groove; 115. Positioning slider; 116. Strip-shaped through hole; 117. Tightening screw; 118. Compression knob; 119. Adjustment slider; 120. Transmission rotating shaft;

[0038] 201. Heating probe; 202. Reference probe; 203. Storage battery;

[0039] 301. Outlet; 302. Maintenance box door; 303. Observation window. Detailed implementation mode

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] Embodiment 1

[0042] This embodiment provides a plant stem flow measurement device, as Figures 1 to 9 shown, including a probe adjustment frame 1, on which a plant stem flow meter 2 is installed. The probe adjustment frame 1 includes a first positioning guide rail 102, a second positioning guide rail 103, an adjustment mounting plate 104 and an adjustment mechanism. The first positioning guide rail 102 and the second positioning guide rail 103 are arranged at intervals and parallel to each other. The ends of the first positioning guide rail 102 and the second positioning guide rail 103 are respectively provided with a first positioning port 106 and a second positioning port 107. The first positioning port 106 and the second positioning port 107 are used to coaxially buckle on the plant stem to vertically position the first positioning guide rail 102 and the second positioning guide rail 103 on the plant stem. The two ends of the adjustment mounting plate 104 are respectively slidably connected to the first positioning guide rail 102 and the second positioning guide rail 103. The adjustment mechanism includes a driving component, which is used to control the moving distance of the adjustment mounting plate 104 on the first positioning guide rail 102 and the second positioning guide rail 103. The heating probe 201 and the reference probe 202 of the plant stem flow meter 2 are both fixed on the plate surface of the adjustment mounting plate 104 facing the first positioning port 106. The heating probe 201 and the reference probe 202 are located on the central connection line between the first positioning port 106 and the second positioning port 107, and the axes of the heating probe 201 and the reference probe 202 are both parallel to the first positioning guide rail 102, so that when the first positioning port 106 and the second positioning port 107 are buckled on the plant stem, the heating probe 201 and the reference probe 202 are also vertically facing the plant stem. The heating probe 201 and the reference probe 202 are respectively close to the first positioning guide rail 102 and the second positioning guide rail 103, and there is a safety distance between the heating probe 201 and the reference probe 202 to ensure that the two do not interfere with each other. The safety distance is usually 10 cm to 15 cm. The plant stem flow meter 2 can use a standard stem flow measurement instrument on the market, such as the pin-type plant stem flow measurement instrument of TPJL-1000.

[0043] During use: First, place the first positioning guide rail 102 above and the second positioning guide rail 103 below. Then, fasten the first positioning port 106 and the second positioning port 107 onto the plant stalk, such as the outer wall of bamboo, the trunk of a tree, etc., so that both the first positioning guide rail 102 and the second positioning guide rail 103 are perpendicular to the stalk. At this time, the heating probe 201 and the reference probe 202 are also vertically facing the plant stalk, and the connection line between the heating probe 201 and the reference probe 202 is parallel to the axis of the stalk, that is, on the same vertical line. Then, adjust the vertical position of the probe adjusting frame 1 so that the heating probe 201 and the reference probe 202 are directly opposite two probe holes pre-drilled on the epidermis of the stalk. Then, drive the adjusting and mounting plate 104 to move towards the plant stalk through the driving component of the adjusting mechanism. First, insert the heating probe 201 and the reference probe 202 into the upper and lower two probe holes respectively, and then continue to drive the heating probe 201 and the reference probe 202 according to the preset depth until the preset depth is reached. Finally, start the plant sap flow meter 2, continuously pass an electric current through the heating probe 201 for heating, collect the temperatures of the heating probe 201 and the reference probe 202, obtain the temperature difference, and calculate the sap flow velocity according to the Granier empirical equation. When not in use, the heating probe 201 and the reference probe 202 can be retracted between the two first positioning guide rails 102 and the second positioning guide rail 103, which can effectively fix and protect the probes, avoid damage to key components, improve the service life of the device, and reduce unnecessary economic losses.

[0044] In this embodiment, as Figures 1 to 9 shown, both the first positioning guide rail 102 and the second positioning guide rail 103 are U-shaped guide rails, and linear sliding grooves 105 are provided on both opposite surfaces of the U-shaped guide rails. One adjusting slider 119 is fixed at each end of the adjusting and mounting plate 104. The adjusting slider 119 is slidably connected in the two linear sliding grooves 105 of the U-shaped guide rail. Preferably, the cross-section of the linear sliding groove 105 is T-shaped, and T-shaped blocks are provided on both sides of the adjusting slider 119, and the T-shaped blocks are embedded in the linear sliding groove 105.

[0045] In this embodiment, as Figures 1 to 9As shown in the figure, the adjusting mechanism includes an adjusting knob 108, an adjusting gear 109, and an adjusting rack 110. The adjusting rack 110 is fixed to one side of the adjusting slider 119, and the adjusting rack 110 is parallel to the linear chute 105. The adjusting knob 108 is rotatably connected to the outer wall of the U-shaped guide rail, specifically on one of the arms of the U-shaped guide rail. A gear mounting groove 111 is provided on the U-shaped guide rail, and the gear mounting groove 111 communicates with the linear chute 105 close to the adjusting knob 108. The adjusting rack 110 is located in this linear chute 105. The adjusting gear 109 is rotatably connected in the gear mounting groove 111, and the adjusting gear 109 meshes with the adjusting rack 110. The adjusting knob 108 is coaxially and fixedly connected to the adjusting gear 109. By rotating the adjusting knob 108, the adjusting gear 109 can be driven to rotate, and then the adjusting rack 110 can be driven to move along the linear chute 105, so as to drive the adjusting slider 119 to move along the linear chute 105, and finally drive the adjusting mounting plate 104 to move along the direction of the linear chute 105. A scale ring 112 is provided on the outer wall of the U-shaped guide rail, and the scale ring 112 is coaxially arranged with the adjusting knob 108 to quantify the rotation angle of the adjusting knob 108 into the moving distance of the adjusting mounting plate 104. For this purpose, an indicating arrow is provided on the adjusting knob 108. Preferably, the accuracy of the scale ring 112 is less than 1 mm.

[0046] Furthermore, in this embodiment, as Figure 5 shown in the figure, in order to ensure that the adjusting mounting plate 104 rises horizontally, the two adjusting gears 109 in the first positioning guide rail 102 and the second positioning guide rail 103 are connected by a transmission rotating shaft 120. In this way, when the adjusting knob 108 is rotated, the two adjusting gears 109 will rotate synchronously.

[0047] In order to adapt to plant stems with different thicknesses, in this embodiment, as Figures 6 to 9As shown in the figure, a positioning mechanism is provided on the side wall of the U-shaped guide rail. The positioning mechanism includes a positioning cross plate 113. A guide chute 114 parallel to the adjustment mounting plate 104 is provided on the positioning cross plate 113. Two positioning sliders 115 are slidably connected in the guide chute 114. The two positioning sliders 115 on the first positioning guide rail 102 are used to form a first positioning opening 106, and the two positioning sliders 115 on the second positioning guide rail 103 are used to form a second positioning opening 107. A threaded deep hole is provided on the surface of the positioning slider 115 that fits the guide chute 114. A strip-shaped through hole 116 is provided on the bottom wall of the guide chute 114. A tightening screw 117 passing through the strip-shaped through hole 116 is threadedly connected in the threaded deep hole. One end of the tightening screw 117 passing through the strip-shaped through hole 116 is fixedly connected with a pressing knob 118. By rotating the pressing knob 118 to make the tightening screw 117 penetrate into the threaded deep hole, the pressing knob 118 can be pressed against the positioning cross plate 113 to lock the positioning slider 115 and the guide chute 114. By rotating the pressing knob 118 in the reverse direction, the pressing knob 118 can be loosened, and at this time, the positioning slider 115 can slide on the guide chute 114. By changing the distance between the positioning sliders 115, the sizes of the first positioning opening 106 and the second positioning opening 107 can be changed to use plant stems with different thicknesses. Preferably, scale lines can be provided on the outer wall of the positioning cross plate 113 to guide the adjustment of the distance between the two positioning sliders 115.

[0048] In this embodiment, as Figures 1 to 9 shown, the probe adjustment frame 1 includes a mounting base 101. The first positioning guide rail 102, the second positioning guide rail 103, and the plant sap flow meter 2 are all fixed on the mounting base 101.

[0049] In this embodiment, as Figures 1 to 9 shown, it includes a protection box 3 with an installation cavity inside. The mounting base 101 is fixed in the installation cavity. An extension port 301 is provided on the outer wall of the protection box 3. The extension port 301 communicates with the installation cavity for the first positioning guide rail 102 and the second positioning guide rail 103 to extend out of the installation cavity. When the protection box 3 is not in use, it can be placed vertically as Figure 1 shown. When in use, hold the protection box 3 horizontally by hand. If used for a long time, a bracket can be used to hold the protection box 3 horizontally. When not in use, the heating probe 201 and the reference probe 202 can be retracted between the two first positioning guide rails 102 and the second positioning guide rails 103, and thus retracted into the interior of the protection box 3, which can effectively fix and protect the probes.

[0050] Furthermore, in this embodiment, as Figures 1 to 9 shown, a storage battery 203 for powering the plant sap flow meter 2 is provided in the installation cavity.

[0051] In this embodiment, as Figures 1 to 9As shown in the figure, a maintenance opening communicating with the installation cavity is provided on the protection box 3. A maintenance box door 302 is hinged at the maintenance opening, and an observation window 303 for observing the inside of the installation cavity is provided on the maintenance box door 302.

[0052] Embodiment 2

[0053] This embodiment provides a method for measuring the stem flow of hollow-stem plants, which adopts the plant stem flow measuring device in Embodiment 1. As Figures 1 to 9 shown, it includes the following steps:

[0054] S1. Measure the wall thickness of the stem of the hollow-stem plant (such as bamboo plants, measure the bamboo wall), select the measurement position, and preset the penetration depths of the heating probe 201 and the reference probe 202.

[0055] S2. Drill heating needle holes and reference needle holes arranged vertically on the stem epidermis of the hollow-stem plant. The connection line of the heating needle holes and the reference needle holes is parallel to the axis of the stem of the hollow-stem plant, that is, on the same vertical line. Select a drill bit with a diameter corresponding to the probe for drilling.

[0056] S3. Fasten the first positioning port 106 and the second positioning port 107 vertically on the stem of the hollow-stem plant, and align the heating probe 201 and the reference probe 202 with the heating needle hole and the reference needle hole respectively. Drive the adjustment mounting plate 104 to move by the adjustment mechanism, so that the heating probe 201 and the reference probe 202 penetrate into the heating needle hole and the reference needle hole respectively according to the preset penetration depths.

[0057] S4. Continuously pass current through the heating probe 201 to heat it, measure the temperature difference between the heating probe 201 and the reference probe 202, and calculate the stem flow velocity according to the Granier empirical equation.

[0058] In this embodiment, as Figures 1 to 9 shown, in step S1, select a reference hollow-stem plant with the same growth trend as the stem of the measured hollow-stem plant, cut off the reference hollow-stem plant, and measure the wall thickness of the stem of the reference hollow-stem plant with a vernier caliper. Since hollow-stem plants have hollow piths, it is not easy to directly measure, especially bamboo plants. Referring to standards such as the Test Methods for Physical and Mechanical Properties of Bamboo (Standard No.: GB / T15780-1995), the method of felling is mostly used to measure the bamboo wall thickness now. Find bamboo plants with similar bamboo ages and bamboo diameters to the measurement target, and use a vernier caliper to measure after felling.

[0059] In the present invention, specific examples are used to illustrate the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A plant stem flow measurement device, characterized in that, It includes a probe adjusting frame installed with a plant sap flow meter. The probe adjusting frame includes a first positioning guide rail, a second positioning guide rail, an adjusting mounting plate and an adjusting mechanism. The first positioning guide rail and the second positioning guide rail are arranged at intervals and parallel to each other. The end parts of the first positioning guide rail and the second positioning guide rail are respectively provided with a first positioning port and a second positioning port for coaxially fastening on the plant stalk. The two ends of the adjusting mounting plate are respectively slidably connected to the first positioning guide rail and the second positioning guide rail. The adjusting mechanism includes a driving component for controlling the moving distance of the adjusting mounting plate. The heating probe and the reference probe of the plant sap flow meter are both fixed on the plate surface of the adjusting mounting plate facing the first positioning port. The heating probe and the reference probe are located on the central connection line between the first positioning port and the second positioning port. The heating probe and the reference probe are respectively close to the first positioning guide rail and the second positioning guide rail. There is a safety distance between the heating probe and the reference probe to ensure that the two do not interfere with each other. The axes of the heating probe and the reference probe are both parallel to the first positioning guide rail; Both the first positioning guide rail and the second positioning guide rail are U-shaped guide rails. Linear sliding grooves are provided on the facing surfaces of the U-shaped guide rails. The adjusting mounting plate is slidably connected to the linear sliding grooves through adjusting sliders. A positioning mechanism is provided on the side wall of the U-shaped guide rail. The positioning mechanism includes a positioning cross plate. A guiding sliding groove parallel to the adjusting mounting plate is provided on the positioning cross plate. Two positioning sliders for forming the first positioning port or the second positioning port are slidably connected in the guiding sliding groove. A threaded deep hole is provided on the surface of the positioning slider that fits the guiding sliding groove. A strip-shaped through hole is provided on the bottom wall of the guiding sliding groove. A tightening screw passing through the strip-shaped through hole is threadedly connected in the threaded deep hole. One end of the tightening screw passing through the strip-shaped through hole is fixedly connected with a pressing knob that can press on the positioning cross plate.

2. The plant stem flow measuring device according to claim 1, wherein, The adjusting mechanism includes an adjusting knob, an adjusting gear and an adjusting rack fixed on the adjusting slider. The adjusting knob is rotatably connected to the outer wall of the U-shaped guide rail. A gear mounting groove communicated with the linear sliding groove close to the adjusting knob is provided on the U-shaped guide rail. The adjusting gear is rotatably connected in the gear mounting groove and meshes with the adjusting rack. The adjusting rack is parallel to the linear sliding groove. The adjusting knob is coaxially and fixedly connected with the adjusting gear. A scale ring coaxially arranged with the adjusting knob is provided on the outer wall of the U-shaped guide rail.

3. The plant stem flow measuring device according to claim 1, characterized in that, The probe adjusting frame includes a mounting base. The first positioning guide rail, the second positioning guide rail and the plant sap flow meter are fixed on the mounting base.

4. The plant stem flow measuring device according to claim 3, characterized in that, It includes a protection box with an installation cavity inside. The mounting base is fixed in the installation cavity. An extension opening for the first positioning guide rail and the second positioning guide rail to extend out of the installation cavity and communicate is provided on the outer wall of the protection box.

5. The plant stem flow measuring device according to claim 4, characterized in that, A storage battery for supplying power to the plant sap flow meter is provided in the installation cavity.

6. The plant stem flow measuring device according to claim 5, characterized in that, A maintenance opening communicating with the installation cavity is provided on the protection box, a maintenance box door is hinged at the maintenance opening, and an observation window capable of observing the interior of the installation cavity is provided on the maintenance box door.

7. A method for measuring the stem flow of hollow-stem plants, which uses the plant stem flow measuring device described in any one of claims 1-6, characterized in that, It includes the following steps: S1. Measure the wall thickness of the stem of the hollow-stemmed plant, and preset the penetration depths of the heating probe and the reference probe; S2. Drill a heating needle hole and a reference needle hole arranged vertically on the stem epidermis of the hollow-stemmed plant, and the connection line of the heating needle hole and the reference needle hole is parallel to the axis of the stem of the hollow-stemmed plant; S3. Buckle the first positioning opening and the second positioning opening on the stem of the hollow-stemmed plant in a vertical arrangement, and align the heating probe and the reference probe with the heating needle hole and the reference needle hole respectively. Drive the adjustment mounting plate to move a distance through the adjustment mechanism, so that the heating probe and the reference probe respectively penetrate into the heating needle hole and the reference needle hole according to the preset penetration depths; S4. Continuously pass an electric current through the heating probe to heat, measure the temperature difference between the heating probe and the reference probe, and calculate the stem flow velocity according to the Granier empirical equation.

8. A method for measuring the stem flow of hollow-stem plants according to claim 7, characterized in that, In step S1, select a reference hollow-stemmed plant with the same stem growth trend as the measured hollow-stemmed plant, cut off the reference hollow-stemmed plant, and measure the wall thickness of the stem of the reference hollow-stemmed plant with a vernier caliper.

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