Plant water stress control device and plant water stress control method

Abstract

To provide a plant moisture stress controller and methods for controlling plant moisture stress that can avoid a facility environment, in which moisture stress increases to a plant, by using the secondary time derivative value of Humidity Deficit.SOLUTION: A plant moisture stress controller of the present invention has control means 30 and a secondary time derivative value calculating unit 40 for calculating the secondary time derivative value of Humidity Deficit measured by a Humidity Deficit measuring means 11, the humidity in a facility being controlled based on the secondary time derivative value of Humidity Deficit calculated by the secondary time derivative value calculating unit 40.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a water stress control device for plants and a water stress control method for plants grown in facilities. [Background technology]

[0002] Greenhouse horticulture can produce crops more stably than open-field horticulture, ensuring a stable food supply and helping to protect the nation's diet. However, greenhouse horticulture has much higher production costs than open-field horticulture, and in order to maintain a high level of stability in management, technological development is needed to improve yields per unit area. In greenhouse horticulture, attempts have been made to improve yields primarily through temperature control and CO2 application, but yield growth appears to have plateaued with temperature control and CO2 application techniques alone. In recent years, humidity (vapor pressure deficit) control techniques have been implemented, which increase stomatal aperture in leaves to enhance CO2 uptake and promote photosynthesis. However, in crops such as fruit and vegetables where the usable part is not the leaf, there have been cases where increased photosynthesis does not contribute to improved yields. This is thought to be due to a lack of improvement in the translocation of assimilates to the usable parts of the plant. To promote the translocation of assimilates to the usable parts of the plant, it is important to precisely regulate the plant's water stress in addition to temperature, and there is a need to develop water stress regulation techniques. In greenhouse cultivation, humidity control (humidification) is carried out during the day on sunny days when the dryness increases to increase the stomatal opening in the leaves, improving CO2 uptake by the plants and promoting photosynthesis. Instantaneous solar radiation: 0.2 kW m ―2 It has been reported that the yield of fruit and vegetables can be improved by controlling the humidity in a facility by "humidifying at a relative humidity of 60% or less under the above conditions and stopping the humidification when the relative humidity is 80% or more" (Non-Patent Document 1). Patent Documents 1 to 4 and Non-Patent Document 2 disclose cultivation devices having humidity control devices and techniques that simplify the mechanisms of humidity control devices. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-202059 [Patent Document 2] Japanese Patent Application Publication No. 09-271271 [Patent Document 3] A CD-ROM containing the contents of the specification and drawings originally attached to the application of Utility Model Application No. 04-85408 (Utility Model Application No. 06-086436) (issued by the Japan Patent Office on December 20, 1994) [Patent Document 4] Japanese Patent Application Publication No. 01-264930 [Non-patent literature]

[0004] [Non-Patent Document 1] Masae Kinomoto and two others, "Effects of controlling relative humidity using a fine mist cooling system on tomato biometric information and yield quality," Tochigi Agricultural Experiment Station Bulletin, 2013, 71, pp. 27-31 [Non-patent document 2] Kenji Kato and seven others, "Effects of mist spraying and long-term CO2 application on growth and yield in strawberry forcing culture", Aichi Agricultural Research Institute Report, 2015, 47, pp. 51-60 Summary of the Invention [Problem to be solved by the invention]

[0005] In order to improve productivity, it is very important not only to promote photosynthesis but also to promote the distribution of photosynthetic products to the utilization parts. Figure 5 is a graph showing the change in saturation deficit when saturation deficit control is performed. The control area is the case where saturation deficit control is not performed, and the graph shows the change in temperature and saturation deficit for the saturation deficit control area and the control area. In the saturation deficit control area, humidification was carried out between 8:00 and 12:00. As shown in Figure 5, the vapor pressure deficit increases rapidly after the saturation deficit control is stopped (at 12:00), and at that time the plant body is subjected to significant water stress. FIG. 6 is a graph showing changes in the growth of strawberry fruits when the saturation deficit control shown in FIG. 5 is performed. Between 8:00 and 12:00, when saturation deficit control was performed, fruit enlargement was approximately 140% compared to the control area, but when compared over a single day, no effect on fruit enlargement was observed, suggesting that the effect of promoting enlargement was negated by the water stress after saturation deficit control. FIG. 7 is a graph showing the rate of change in stalk diameter, the rate of fruit enlargement, and the change in vapor pressure deficit. As shown in Figure 7, the fruit enlargement rate is similar to the rate of change in stalk diameter, indicating that fruit enlargement is strongly affected by the water stress state of the plant. However, no relationship can be detected between the fruit enlargement rate and the vapor pressure deficit. On the other hand, Figure 8 is a graph showing the rate of change in stalk diameter and the change in the second derivative of vapor pressure deficit over time. The inventors discovered that by focusing on the relationship between the rate of change in stalk diameter and the second derivative of the vapor pressure deficit over time, as shown in Figure 8, it is possible to suppress the increase in water stress on the plant body.

[0006] The present invention aims to provide a water stress control device for plants and a water stress control method for plants that can avoid an in-facility environment that increases water stress on plants by using the second-order derivative of the vapor pressure deficit over time. [Means for solving the problem]

[0007] The water stress control device for a plant body according to the first embodiment of the present invention is a water stress control device for a plant body grown in a facility, comprising: a vapor saturation deficit measuring means 11 for measuring a vapor saturation deficit in the facility; and a control means 30 for controlling a humidifying means 20 for humidifying the facility, wherein the control means 30 includes a second-order differential value calculating unit 40 for calculating a second-order differential value of the vapor saturation deficit measured by the vapor saturation deficit measuring means 11. a second-order differential value comparison unit (41) that compares the time-dependent second-order differential value of the vapor saturation deficit calculated by the second-order differential value calculation unit (40) with a second-order differential setting value; and an output unit (42) that operates the humidifying means (20) when the second-order differential value comparison unit (41) determines that the time-dependent second-order differential value of the vapor saturation deficit is equal to or greater than the second-order differential setting value. Equipped with Ruko It is characterized by the following. The present invention No. 2 The embodiment of the present invention is No. 1In the embodiment of the device for controlling water stress in a plant body, the control means 30 includes a first-order derivative calculation unit 37 that calculates a time-first derivative of the vapor saturation deficit measured by the vapor saturation deficit measurement means 11, and a first-order derivative comparison unit 39 that compares the time-first derivative of the vapor saturation deficit calculated by the first-order derivative calculation unit 37 with a first-order derivative setting value, and the output unit 42 operates the humidifying means 20 when it is determined that the time-first derivative of the vapor saturation deficit is equal to or greater than the first-order derivative setting value and that the time-second derivative of the vapor saturation deficit is equal to or greater than the second-order derivative setting value, and does not operate the humidifying means 20 when it is determined that the time-first derivative of the vapor saturation deficit is less than the first-order derivative setting value. The present invention Third The embodiment of the present invention is No. 1 In the embodiment of the device for controlling water stress in a plant body, the control means 30 includes a vapor deficit comparison unit 36 ​​that compares the vapor deficit measured by the vapor deficit measurement means 11 with a vapor deficit set value, and the output unit 42 operates the humidifying means 20 when the vapor deficit comparison unit 36 ​​determines that the vapor deficit is equal to or greater than the vapor deficit set value and that the time second derivative value of the vapor deficit is equal to or greater than the second derivative set value, and does not operate the humidifying means 20 when it determines that the vapor deficit is less than the vapor deficit set value. The present invention Fourth The embodiment of the present invention is No. 1 In the embodiment of the water stress control device for a plant body, a time setting means 13 is provided for setting an operation time for operating the humidifying means 20, and the output unit 42 operates the humidifying means 20 when it is determined that the operation time of the humidifying means 20 set by the time setting means 13 and the time second derivative value of the vapor pressure deficit is equal to or greater than the second derivative set value, and does not operate the humidifying means 20 unless the operation time of the humidifying means 20 set by the time setting means 13 is reached. The present invention No. 5 The water stress control method for plants according to the embodiment is a method for controlling water stress in plants grown in a facility, characterized in that when a vapor pressure deficit in the facility is equal to or greater than a vapor pressure deficit set value and a time second derivative value of the vapor pressure deficit is equal to or greater than a second derivative set value, the facility is humidified. The present invention No. 6 The water stress control method for plants according to the embodiment is a method for controlling water stress in plants grown in a facility, characterized in that when a vapor pressure deficit in the facility is equal to or greater than a vapor pressure deficit set value, a first-order derivative value of the vapor pressure deficit over time is equal to or greater than a first-order derivative set value, and a second-order derivative value of the vapor pressure deficit over time is equal to or greater than a second-order derivative set value, the facility is humidified. [Effects of the Invention]

[0008] According to the present invention, by operating the humidifying means when it is determined that the time second derivative value of the vapor pressure deficit is equal to or less than the second derivative set value, it is possible to avoid an environment within the facility in which water stress on the plants increases. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a block diagram showing a water stress control device for a plant body according to an embodiment of the present invention, with functional implementation means. [Figure 2] 1 is a flowchart showing a method for controlling water stress in a plant according to the present embodiment. [Figure 3] Graph showing the number of times a plant body is subjected to severe stress by the method for controlling water stress of this example. [Figure 4] The results of the "water stress control area" and "control area" shown in Figure 3 are shown. [Figure 5] Graph showing the change in saturation deficit when saturation deficit control is performed [Figure 6] Graph showing changes in strawberry fruit growth when saturation deficit control is performed as shown in Figure 5 [Figure 7] Graph showing the rate of change in stalk diameter, fruit growth rate, and vapor pressure deficit [Figure 8] Graph showing the rate of change in peduncle diameter and the change in the second derivative of vapor pressure deficit DETAILED DESCRIPTION OF THE INVENTION

[0010] In the water stress control device for a plant according to the first embodiment of the present invention, the control means includes a second derivative value calculation unit that calculates a time second derivative value of the vapor pressure deficit measured by the vapor pressure deficit measurement means. a second-order differential value comparison unit that compares the time second-order differential value of the saturation deficit calculated by the second-order differential value calculation unit with a second-order differential set value; and an output unit that operates the humidifying means when the second-order differential value comparison unit determines that the time second-order differential value of the saturation deficit is equal to or greater than the second-order differential set value. Equipped with Rumo That is why. According to this embodiment, by controlling the humidity inside the facility based on the second derivative of the vapor pressure deficit over time using, for example, a humidifying means or a dehumidifying means, it is possible to avoid an environment inside the facility that increases water stress on plants. Furthermore, if the second-order derivative value comparison unit determines that the time second-order derivative value of the vapor pressure deficit is equal to or greater than the second-order derivative setting value, the humidifying means is operated to avoid an environment within the facility that increases water stress on the plants.

[0011] The present invention No. 2 The embodiment of the present invention is No. 1 In the embodiment of the device for controlling water stress in a plant body, the control means includes a first-order derivative calculation section that calculates a time-first derivative value of the saturation deficit measured by the saturation deficit measurement means, and a first-order derivative comparison section that compares the time-first derivative value of the saturation deficit calculated by the first-order derivative calculation section with a first-order derivative set value, and the output section operates the humidifying means when it is determined that the time-first derivative value of the saturation deficit is equal to or greater than the first-order derivative set value and the time-second derivative value of the saturation deficit is equal to or greater than the second-order derivative set value, and does not operate the humidifying means when it is determined that the time-first derivative value of the saturation deficit is less than the first-order derivative set value. According to this embodiment, when it is determined that the time-first derivative value of the vapor pressure deficit is equal to or greater than the first derivative set value and the time-second derivative value of the vapor pressure deficit is equal to or greater than the second derivative set value, the humidifying means is operated, thereby making it possible to avoid an environment within the facility in which water stress on the plants increases.

[0012] The present invention Third The embodiment of the present invention is No. 1 In the embodiment of the device for controlling water stress in a plant body, the control means includes a saturation deficit comparison unit that compares the saturation deficit measured by the saturation deficit measurement means with a saturation deficit set value, and the output unit operates the humidifying means when the saturation deficit comparison unit determines that the saturation deficit is equal to or greater than the saturation deficit set value and that the time second derivative value of the saturation deficit is equal to or greater than the second derivative set value, and does not operate the humidifying means when it determines that the saturation deficit is less than the saturation deficit set value. According to this embodiment, water stress in plants increases in an environment within a facility where the vapor pressure deficit is large, so by avoiding an environment within a facility where the vapor pressure deficit is large, water stress in plants can be reduced.

[0013] The present invention Fourth The embodiment of the present invention is No. 1 In the embodiment of the water stress control device for a plant body, a time setting means is provided for setting the operation time for operating the humidifying means, and the output section operates the humidifying means when it is determined that the operation time for the humidifying means set by the time setting means and the time second derivative value of the saturation deficit is equal to or greater than the second derivative set value, and does not operate the humidifying means unless it is the operation time for the humidifying means set by the time setting means. According to this embodiment, since the vapor pressure deficit increases as the cumulative solar radiation increases, by setting in advance the time when the cumulative solar radiation increases, it is possible to avoid an environment within the facility where the vapor pressure deficit increases and reduce water stress on the plant body.

[0014] The present invention No. 5 The method for controlling water stress in a plant according to the embodiment humidifies the inside of the facility when the vapor pressure deficit in the facility is equal to or greater than a vapor pressure deficit set value and the time second derivative value of the vapor pressure deficit is equal to or greater than a second derivative set value. According to this embodiment, if the time second derivative value of the vapor pressure deficit is equal to or greater than the second derivative setting value, the water stress of the plant body increases. Therefore, by avoiding an environment within the facility where the vapor pressure deficit becomes large, the water stress of the plant body can be reduced.

[0015] The present invention No. 6 The method for controlling water stress in a plant body according to the embodiment is to humidify the facility when the vapor pressure deficit within the facility is equal to or greater than a vapor pressure deficit set value, the first derivative value of the vapor pressure deficit over time is equal to or greater than a first derivative set value, and further the second derivative value of the vapor pressure deficit over time is equal to or greater than a second derivative set value. According to this embodiment, if the vapor pressure deficit within the facility is equal to or greater than the vapor pressure deficit set value, the time first derivative value of the vapor pressure deficit is equal to or greater than the first derivative set value, and the time second derivative value of the vapor pressure deficit is equal to or greater than the second derivative set value, the water stress of the plant body will increase. Therefore, by avoiding an environment within the facility where the vapor pressure deficit becomes large, the water stress of the plant body can be reduced. [Example]

[0016] An embodiment of a water stress control device for a plant according to the present invention will now be described. FIG. 1 is a block diagram showing the water stress control device for a plant body according to this embodiment in terms of function realization means. The water stress control device for a plant according to this embodiment comprises a saturation deficit measuring means 11 that measures the saturation deficit within the facility, a set value input means 12 that can input a set value, a time setting means 13 that sets the operation time for operating the humidifying means 20, and a control means 30 that controls the humidifying means 20 that humidifies the facility. The saturation deficit measuring means 11 measures the saturation deficit intermittently or continuously.

[0017] The control means 30 includes a saturation deficit memory unit 31 that stores the saturation deficit measured by the saturation deficit measuring means 11, a saturation deficit set value memory unit 32 that stores the saturation deficit set value input by the set value input means 12, a first derivative set value memory unit 33 that stores the first derivative set value input by the set value input means 12, a second derivative set value memory unit 34 that stores the second derivative set value input by the set value input means 12, and an operation time memory unit 35 that stores the operation time set by the time setting means 13.

[0018] The control means 30 also includes a saturation deficit comparison unit 36 ​​that compares the saturation deficit measured by the saturation deficit measurement means 11 with a saturation deficit set value, a first-order derivative calculation unit 37 that calculates a time-first derivative of the saturation deficit measured by the saturation deficit measurement means 11, a first-order derivative storage unit 38 that stores the time-first derivative of the saturation deficit calculated by the first-order derivative calculation unit 37, a first-order derivative comparison unit 39 that compares the time-first derivative of the saturation deficit calculated by the first-order derivative calculation unit 37 with the first-order derivative set value, a second-order derivative calculation unit 40 that calculates a time-second order derivative of the saturation deficit measured by the saturation deficit measurement means 11, a second-order derivative comparison unit 41 that compares the time-second order derivative of the saturation deficit calculated by the second-order derivative calculation unit 40 with the second-order derivative set value, and a second-order derivative storage unit 43 that stores the time-second order derivative of the saturation deficit calculated by the second-order derivative calculation unit 40. The saturation deficit comparison unit 36 ​​compares the saturation deficit stored in the saturation deficit storage unit 31 with the saturation deficit set value stored in the saturation deficit set value storage unit 32 . The first-order differential value calculation unit 37 calculates the first-order temporal differential value of the time-series vapor saturation deficit stored in the vapor saturation deficit storage unit 31. Note that, in calculating the first-order temporal differential value, for example, an instantaneous value or an average value over a predetermined time period can be used. The first-order derivative value comparison unit 39 compares the time first-order derivative value of the saturation deficit calculated by the first-order derivative value calculation unit 37 with the first-order derivative setting value stored in the first-order derivative setting value storage unit 33 . The time-first differential value of the vapor saturation deficit is, for example, the amount of change in the vapor saturation deficit data over the past five minutes, but the calculation of the time-first differential value of the vapor saturation deficit is not limited to this. The second derivative calculation unit 40 calculates the second derivative of the vapor saturation deficit over time using the time series vapor saturation deficit stored in the vapor saturation deficit storage unit 31. Note that, in calculating the second derivative of the vapor saturation deficit over time, for example, an instantaneous value or an average value over a predetermined time period can be used. The second temporal derivative of the vapor saturation deficit can be obtained by further differentiating, with time, the first temporal derivative obtained by differentiating the vapor saturation deficit with time. The second temporal derivative is, for example, the amount of change in the first temporal derivative over the past minute. However, the calculation of the second temporal derivative of the vapor saturation deficit is not limited to this. The second derivative value comparison unit 41 compares the time second derivative value of the saturation deficit calculated by the second derivative value calculation unit 40 with the second derivative setting value stored in the second derivative setting value storage unit 34 .

[0019] The control means 30 includes an output unit 42 that operates the humidifying means 20. The output unit 42 may operate the dehumidifying means together with the humidifying means 20, or may operate the dehumidifying means instead of the humidifying means 20.

[0020] FIG. 2 is a flow chart showing the method for controlling water stress in a plant body according to this embodiment. The method for controlling water stress in a plant according to this embodiment is carried out on a plant cultivated in a facility through the following steps.

[0021] First, in S1, it is determined whether the operation time is one of the times stored in the operation time memory unit 35. If it is not the operation time, the saturation deficit measurement means 11 is stopped (S2). When the operation time arrives, the saturation deficit measurement means 11 starts measuring the saturation deficit (S3). The operation time is, for example, from 6:00 to 18:00. The humidifying means 20 will not operate unless it is the operation time set by the time setting means 13. The saturation deficit increases as the cumulative solar radiation increases. Therefore, by setting in advance the time when the cumulative solar radiation increases, it is possible to avoid an environment within the facility where the saturation deficit increases, and reduce water stress on the plant body. When measurement by the saturation deficit measuring means 11 is started, the saturation deficit comparing section 36 compares the saturation deficit with a saturation deficit set value (S4). If the saturation deficit is equal to or greater than the saturation deficit set value in S4, the first derivative value comparison unit 39 determines whether the time first derivative value of the saturation deficit is equal to or greater than the first derivative set value (S5). If it is determined in S5 that the time-first derivative of the saturation deficit is equal to or greater than the first derivative setting, the second derivative comparing unit 41 compares the time-second derivative of the saturation deficit with the second derivative setting (S6). If the time second derivative value of the vapor saturation deficit is equal to or greater than the second derivative setting value in S6, the humidifying means 20 is operated (S7). In addition, if the vapor saturation deficit is less than the vapor saturation deficit set value in S4, if the time-first derivative value of the vapor saturation deficit is less than the first derivative set value in S5, or if the time-second derivative value of the vapor saturation deficit is less than the second derivative set value in S6, the humidifying means 20 is not operated, and measurement by the vapor saturation deficit measuring means 11 continues if it is within the set time.

[0022] The method for controlling water stress in plants according to this embodiment avoids stress that occurs when the diameter of the fruit stalk shrinks suddenly, and by humidifying the facility when the second derivative value of the vapor pressure deficit over time within the facility is equal to or greater than the second derivative setting value, it is possible to avoid an environment within the facility that increases water stress on the plants. Furthermore, since water stress in plants increases in an environment within a facility where the vapor pressure deficit is increasing, the method for controlling water stress in plants according to this embodiment humidifies the facility when the time-first derivative value of the vapor pressure deficit within the facility is equal to or greater than the set first derivative value and the time-second derivative value of the vapor pressure deficit is equal to or greater than the set second derivative value, thereby avoiding an environment within the facility where the vapor pressure deficit is increasing and reducing water stress in the plants. Furthermore, since water stress in plants increases in an environment within a facility where the vapor pressure deficit is large, the method for controlling water stress in plants according to this embodiment humidifies the facility when the vapor pressure deficit in the facility is equal to or greater than the vapor pressure deficit set value, the first-order time derivative of the vapor pressure deficit is equal to or greater than the first-order derivative set value, and further the second-order time derivative of the vapor pressure deficit is equal to or greater than the second-order derivative set value, thereby making it possible to avoid an environment within the facility where the vapor pressure deficit becomes large and reduce water stress in plants.

[0023] The following describes the results of the demonstration of the method for controlling water stress in plants according to this example. 3 is a graph showing the number of times severe stress was encountered in plants using the method for controlling water stress in this example. The "control group" is the case where the method for controlling water stress in plants in this example was not used. The "water stress-adjusted group" is the case where the method for controlling water stress in plants in this example was used, and the number of times severe stress was encountered on each day over five days is compared with the "control group." In the method for controlling water stress in a plant body of this example, the vapor pressure deficit setting value in S4 is 7 hPa, and the first derivative setting value in S5 is 0.1 hPa·h ―1 , the second derivative setting value in S6 is -0.004 hPa·h -2 It states that: Strawberries were used as the plant body, and when the vapor pressure deficit was 10 hPa or higher and the first and second time derivatives of the stalk diameter were less than zero, i.e., when the stalk diameter rapidly shrank, it was counted as severe stress. As shown in Figure 3, in the "water stress adjustment area" compared to the "control area," the number of times severe stress was experienced was reduced on each of the five days, but the total number of times severe stress was experienced over the five days was reduced by 37%.

[0024] Figure 4 shows the results of the "water stress adjustment area" and the "control area" shown in Figure 3, where Figure 4(a) is a graph showing the relationship between the number of times severe stress was encountered and the daily accumulated solar radiation, and Figure 4(b) is a graph comparing the fruit weight at harvest. As shown in Figure 4(a), when the natural logarithm of the difference in the number of times severe stress was encountered between the "control area" and the "water stress-adjusted area" (In (difference in the number of times severe stress was encountered)) was regressed on the daily accumulated solar radiation, a strong positive correlation was found at the 5% significance level (p=0.025). From this, it can be said that the method for controlling water stress in plants in this example is more effective in reducing the number of times the plant experiences severe stress on sunny days, i.e., days with more solar radiation. Furthermore, as shown in FIG. 4(b), in the "water stress adjustment zone" according to the method for controlling water stress in plants of this example, water stress was alleviated, fruit enlargement was promoted, and fruit weight was significantly increased. [Industrial Applicability]

[0025] The plant water stress control device and plant water stress control method according to the present invention are suitable for plants cultivated in facilities, such as fruit trees and ornamental plants, as well as fruit and leafy vegetables. [Explanation of symbols]

[0026] 11 Saturation deficit measurement method 12 Setting value input means 13 Time setting means 20 Humidification means 30 Control Means 31 Saturation memory section 32 Saturation deficit setting value memory section 33 First derivative setting value memory section 34 Second derivative setting value memory section 35 Operation time storage section 36 Saturation difference comparison section 37 First derivative calculation unit 38 First derivative value storage section 39 First derivative value comparison section 40 Second derivative calculation unit 41 Second derivative value comparison unit 42 Output section 43 Second derivative value storage unit

Claims

1. A water stress control device for a plant body grown in a facility, comprising: a vapor pressure deficit measuring means for measuring a vapor pressure deficit in the facility; and a control means for controlling a humidifying means for humidifying the facility, The control means a second-order differential value calculation unit that calculates a second-order differential value of the vapor pressure deficit measured by the vapor pressure deficit measuring means; a second-order differential value comparison unit that compares the time second-order differential value of the saturation deficit calculated by the second-order differential value calculation unit with a second-order differential setting value; an output unit that operates the humidifying means when the second-order differential value comparison unit determines that the time second-order differential value of the vapor pressure deficit is equal to or greater than the second-order differential setting value, A plant's water stress control device.

2. The control means a first-order differential value calculation unit that calculates a first-order time differential value of the vapor pressure deficit measured by the vapor pressure deficit measuring means; a first-order differential value comparison unit that compares the time first-order differential value of the saturation deficit calculated by the first-order differential value calculation unit with a first-order differential setting value; Equipped with In the output unit, operating the humidifying means when it is determined that the time first derivative value of the vapor pressure deficit is equal to or greater than the first derivative setting value and the time second derivative value of the vapor pressure deficit is equal to or greater than the second derivative setting value; 2. The water stress control device for a plant according to claim 1, wherein the humidifying means is not operated when it is determined that the time first derivative value of the vapor pressure deficit is less than the first derivative setting value.

3. The control means a saturation deficit comparison unit that compares the saturation deficit measured by the saturation deficit measuring means with a saturation deficit set value, In the output unit, When the vapor deficit comparison unit determines that the vapor deficit is equal to or greater than the vapor deficit set value and that the time second derivative value of the vapor deficit is equal to or greater than the second derivative set value, the humidifying means is operated; 2. The water stress control device for a plant according to claim 1, wherein the humidifying means is not operated when it is determined that the vapor pressure deficit is less than the vapor pressure deficit set value.

4. a time setting means for setting an operation time for operating the humidifying means; In the output unit, the time is the operation time of the humidifier set by the time setting means, and when it is determined that the second derivative value with respect to time of the vapor pressure deficit is equal to or greater than the second derivative setting value, the humidifier is operated; 2. The water stress control device for a plant according to claim 1, wherein the humidifying means is not operated unless it is the operation time of the humidifying means set by the time setting means.

5. A method for controlling water stress in a plant cultivated in a facility, comprising: The method for controlling water stress in a plant body includes humidifying the inside of the facility when a vapor deficit in the facility is equal to or greater than a vapor deficit set value and a time second derivative value of the vapor deficit is equal to or greater than a second derivative set value.

6. A method for controlling water stress in a plant cultivated in a facility, comprising: A method for controlling water stress in a plant body, comprising: humidifying the inside of the facility when a vapor pressure deficit within the facility is equal to or greater than a vapor pressure deficit set value; a first-order time derivative value of the vapor pressure deficit is equal to or greater than a first-order time derivative set value; and a second-order time derivative value of the vapor pressure deficit is equal to or greater than a second-order time derivative set value.

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