A modulated fluorescence imager using blue and green light to calculate the photochemical efficiency Φ of leaf photosystem I. PSI Method

Abstract

This invention relates to the field of plant stress diagnosis technology, and more particularly to a modulated fluorescence imager that uses blue and green light to calculate the photochemical efficiency Φ of leaf photosystem I. PSI The method described in this invention utilizes a Mini-PAM chlorophyll fluorometer to measure blue and green light excitation in tomato leaves of both the test and control groups to generate fluorescence. Based on the measurement results, the photochemical efficiency Φ of photosystem I is calculated. PSI This allows for the diagnosis of the condition of the crop under test. The photochemical efficiency Φ of the photosystem I mentioned in this invention... PSI It is more sensitive to stress and is more effective in reflecting adverse stress. It is expected to be applied to the early diagnosis of stress in plants, so as to intervene in time and reduce losses.

Description

Technical Field

[0001] This invention relates to the field of plant stress diagnosis technology, and more particularly to a modulated fluorescence imager that uses blue and green light to calculate the photochemical efficiency Φ of leaf photosystem I. PSI The method. Background Technology

[0002] tomato( Solanum lycopersicum Tomato (L.) is one of the world's most important horticultural crops, widely cultivated both domestically and internationally. In 2022, my country's tomato cultivation area reached 1.1692 million hectares. 2 It has high economic value. As we all know, in daily cultivation and production, tomato plants are often subjected to various stresses such as drought, high temperature, and low temperature, which seriously affect the yield and quality of tomatoes.

[0003] Currently, chlorophyll fluorescence technology is widely used for diagnosing plant physiological states or stress levels. Its working principle can be simply described as follows: chlorophyll absorbs light energy and enters an excited state. The subsequent energy dissipation process, restoring it to its ground state, mainly occurs through three pathways: photochemical reactions (photochemical quenching), thermal dissipation (non-photochemical quenching), and fluorescence. These three pathways compete with each other and achieve a dynamic equilibrium. When plants encounter biotic or abiotic stresses (such as high temperature or drought), photosynthetic structures, such as photosystem II (PSII) reaction centers, are directly damaged, and photosynthetic electron transport is inhibited, thereby disrupting the aforementioned energy distribution balance and leading to F... v / F m (PSII maximum photochemical efficiency), Φ PSII Changes in key fluorescence parameters such as PSII (actual photochemical efficiency) and NPQ (non-photochemical quenching) can quickly diagnose whether plants are under stress and the degree of stress by detecting abnormal fluctuations in these fluorescence parameters.

[0004] Traditional fluorescence measurement techniques have several significant drawbacks. First, traditional excitation light is often blue / red light, which is strongly absorbed by chlorophyll, resulting in high light intensity in the surface tissues of leaves, while the light intensity in deeper tissues decreases sharply. Second, while strong absorption light (blue / red light) can achieve high intensity, it cannot account for the light exposure of leaves in the lower canopy, making it difficult to cover the full functional state of plants from low light adaptation to high light stress. Third, traditional techniques struggle to distinguish between PSII and PSI fluorescence, leading to an underestimation of PSII quantum yield and decreased accuracy in diagnosing crop stress levels. Furthermore, chlorophyll in plants absorbs green light relatively weakly. Previous studies have found that using green light with a wavelength of approximately 530 nm as the excitation source can significantly optimize the uniformity of light exposure across the entire leaf layer, covering the entire physiological scenario from low light adaptation to high light stress. This reduces interference from light-induced photosynthesis measurements on fluorescence and improves the minimum fluorescence intensity for dark adaptation (F). o The accuracy of measurements of core parameters such as ( ).

[0005] Meanwhile, traditional fluorescence detection techniques are mainly based on F v / F m The degree of stress experienced by the leaves was assessed using equivalent methods. F v / F m A decrease does not necessarily equate to a decline in photosynthetic efficiency; it could be due to unrecovered non-photochemical quenching rather than PSII damage. Furthermore, using only blue light as excitation has drawbacks such as poor illumination uniformity, narrow coverage of photochemical efficiency, and PSI fluorescence interference. In comparison, the photochemical efficiency of photosystem I (Φ) PSI ) than F v / F m It can better reflect the physiological state of leaves. A calculation method needs to be designed to derive the photosystem I parameters of plant leaves, which will more efficiently diagnose the physiological state and stress level of plants. Summary of the Invention

[0006] To improve the efficiency of fluorescence detection technology in diagnosing crop physiological states and stress levels, this invention adds green light as the excitation light for detection and establishes a derived formula to calculate the system's photochemical efficiency (Φ). PSI This paper proposes a method for calculating the photochemical efficiency Φ of the leaf photosystem I using a modulated fluorescence imager with both blue and green measurement lights. PSI The method.

[0007] The specific technical solution is as follows: In one aspect, the present invention provides a method for calculating the photochemical efficiency Φ of a leaf photosystem I. PSI The method includes the following steps: S1. Illuminate the leaf under test with blue and green light measurement light, and detect and record the initial fluorescence F generated by blue light excitation. o B and maximum fluorescence F m B The initial fluorescence F generated by green light excitation o G and maximum fluorescence F m G ; S2. Calculate the photochemical efficiency Φ of photosystem I using the following formula. PSI ; The photochemical efficiency Φ of the optical system I PSI The calculation formula is: (I)Φ PSI =1-1 / k1 (II) k1=1 / (1-γ) G )×F m G / F o G -F mB / F o B ×γ G / (1-γ G ) (III)γ G =F o G (c) / F o G (t)×F o B (t) / F o B (c)×γ G (c) In equation (I), k1 refers to the photosynthetic parameter of PSI, i.e., k1 = F m G (1) / F o G (1) ; Subscript （1） Represents optical system I.

[0008] In the formula (II), γ G For measuring the effect of PSII on initial fluorescence F under green light o G The contribution coefficient; In the aforementioned formula (III), F o G (c) and / F o B (c) The initial fluorescence of the control group leaves under green and blue light measurement, respectively. o G (t) and F o B (t) represents the initial fluorescence of the leaf under green and blue light measurement, respectively, γ G (c) represents the contribution coefficient of PSII to the initial fluorescence of the control group leaves under green light measurement.

[0009] Furthermore, the control group leaves are leaves from healthy plants under normal growth conditions, and the γ G (c) Set to 0.7.

[0010] Furthermore, the healthy plant is a healthy plant that grows under normal and suitable environmental conditions and is not subjected to environmental stress.

[0011] Under dark-adapted conditions, when the PSII reaction center is fully open (F oUnder the measurement conditions, the fluorescence contributions of PSI and PSII follow the following pattern due to the differences in their inherent spectral absorption characteristics: In the blue light band (450-500nm), the light-harvesting complex (LHC II) of PSII can efficiently absorb excitation light through chlorophyll b and carotenoids, and its fluorescence contribution is significantly higher than that of PSI. The proportion of PSI is extremely small and can be ignored. It can be concluded that the result obtained under subsequent blue light measurement is only PSII. In the green light band (500-550nm), although PSII still has the advantage, its proportion decreases due to its lower absorption efficiency of green light. PSI, on the other hand, has a relatively higher fluorescence contribution due to the specific absorption of related carotenoids.

[0012] Furthermore, the blade under test undergoes a dark adaptation treatment for at least 30 minutes before measurement.

[0013] After the leaves of the plant to be tested are dark-adapted for more than 30 minutes, the PSII reaction center of the plant can be fully opened, and the energy dissipation pathways such as non-photochemical quenching can be restored to the basic state, eliminating the fluorescence signal fluctuations caused by residual light, so as to obtain stable and reliable initial fluorescence (Fo) and maximum fluorescence (Fm), and ensure the accuracy of chlorophyll fluorescence parameter measurement.

[0014] Furthermore, both the test leaf and the control group leaf are mature functional leaves.

[0015] Furthermore, the mature functional leaf is a mid-level functional leaf in which the plant is fully expanded, growing vigorously, without damage or aging, and with stable and vigorous photosynthetic physiological activity.

[0016] Using mature functional leaves for chlorophyll fluorescence measurement can avoid interference from immature young leaves and declining physiological functions in older leaves. The photosynthetic structure of the leaves is uniform and stable, which can significantly improve the accuracy, repeatability and representativeness of the test results.

[0017] Furthermore, the measuring instrument is preferably a Mini-PAM chlorophyll fluorometer.

[0018] Furthermore, the Mini-PAM chlorophyll fluorometer contains 12 blue LEDs and 12 green LEDs, arranged in a staggered ring, with a maximum power of 2 W per LED.

[0019] Furthermore, the main peak of the blue light measurement light is 440~470 nm, and the main peak of the green light measurement light is 510~530 nm.

[0020] Furthermore, the main peak wavelength of the blue light measurement light is preferably 450 nm, and the main peak wavelength of the green light measurement light is preferably 520 nm.

[0021] Furthermore, the pulse width of the blue light measurement light and the green light measurement light is 30~50 μs, and the frequency is 5~15 Hz.

[0022] Furthermore, the pulse width of the blue light measurement light and the green light measurement light is preferably 42 μs, and the frequency is 8 Hz.

[0023] Furthermore, the saturation pulse width used to measure maximum fluorescence is 80~120 μs, and the frequency is 6000~10000 Hz.

[0024] Furthermore, the saturation pulse width used to measure maximum fluorescence is preferably 100 μs, and the frequency is 8000 Hz.

[0025] In another aspect, the present invention provides a method for determining whether a plant is suffering from environmental stress using the above-described method, comprising: The Φ of the plant leaf to be tested PSI Φ value compared to control group leaves PSI Compare the values, if Φ PSI If the value decreases by no less than 15%, the plant is considered to be under environmental stress.

[0026] Furthermore, the environmental stresses include: drought stress, salinity stress, low temperature stress, high temperature stress, and low light stress.

[0027] Furthermore, the environmental stresses include: high temperature stress, drought stress, and low temperature stress.

[0028] Environmental stress can damage plant photosystems. Photosystem I, due to its lower redox potential of electron acceptors, lower repair efficiency, and lack of protective regulatory mechanisms, is more susceptible to irreversible damage than photosystem II. Using the Φ of this invention... PSI The calculation method can better reflect the photochemical reaction efficiency of photosystem I, thus indicating the degree of stress on the plant.

[0029] Furthermore, the plant is preferably a tomato.

[0030] Compared with the prior art, the present invention has the following beneficial effects: (1) The photochemical efficiency Φ of the optical system I, derived and calculated by the method of the present invention PSI It is more sensitive to environmental stress and is expected to be used for early diagnosis of plant stress, so as to detect and intervene in a timely manner and reduce yield loss.

[0031] (2) The method of the present invention can be applied to genetic breeding to screen resistant germplasm, and can also be used to monitor the impact of environmental changes on plant photosynthetic physiology, providing a basis for improving crop cultivation conditions.

[0032] (3) The method of the present invention is conducive to the development of agricultural production towards scientific and refined direction. It can also be applied to expert systems in the field of stress diagnosis to further improve the yield and quality of agricultural products.

[0033] (4) This method is simple to operate, highly accurate, fast and can accurately reflect the physiological state of plants. Attached Figure Description

[0034] Figure 1 This is the interface for setting up the blue and green light measurement using a Mini-PAM fluorescence instrument in the method of this invention. Here, Meas Light represents the measurement light, Act Light represents the photochemical light, Sat Light represents the saturation light, B represents blue light, and G represents green light.

[0035] Figure 2 This is the data collection interface for measurements taken under blue and green light using a Mini-PAM fluorescence spectrometer in this invention. The values ​​in column F represent F... o F m 'Column value is F' m The values ​​in column Y(Ⅱ) are F v / F m .

[0036] Figure 3 To calculate the photochemical efficiency Φ of optical system I according to the calculation formula of this invention PSI Subsequently, box plots and decrease rates were generated for the control group, high temperature group, drought group, and low temperature group using GraphPadPrism 8 software.

[0037] Figure 4 To obtain F directly using a Mini-PAM fluorescence spectrometer v B / F m B Box plots and decrease rates were generated for the control group, high temperature group, drought group, and low temperature group using GraphPad Prism 8 software. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer.

[0039] Example 1, Photochemical efficiency (Φ) of photosystem I (PSI) PSI Derivation of the calculation formula (1-1) Given F v / F m =1-Fo / F m F in green light measurement mode o G =F o G (1) +F o G (2) F m G =F m G (1) +F m G (2) F o G and F m G These represent the initial fluorescence and maximum fluorescence yield under green light measurement, respectively. F o G (1) and F o G (2) Representing PSI and PSII respectively against F o G F's contribution m G (1) and F m G (2) Representing PSI and PSII respectively against F m G The contribution. Let k = F m / F o Then the optical system I parameter k1=F m G (1) / F o G (1) Optical system II parameter k2=F m G (2) / F o G (2) The derivation yields: k1=(F m G -k2*F o G (2) ) / (F o G -F o G (2) )Formula I (1-2) In the green light measurement light mode, assuming Fo G (2) =γ G *F o G γ G PSII under green light measurement represents the initial fluorescence F o G The contribution coefficient can be obtained by simplifying Equation I. k1=1 / (1-γ G )*F m G / F o G -k2*γ G / (1-γ G Formula II (1-3) In the blue light measurement mode, the obtained data can be considered as only for optical system II, and k2=F m G (2) / F o G (2) =F m B / F o B Substituting into equation II, we finally obtain k1=1 / (1-γ G )*F m G / F o G -F m B / F o B *γ G / (1-γ G Formula III Note: Superscript B indicates blue light measurement, and superscript G indicates green light measurement.

[0040] (1-4) The photochemical efficiency Φ of photosystem I is obtained according to equation III. PSI .

[0041] Φ PSI =1-1 / k1Form IV (1-5) Calculate γ G The derivation process is as follows: Under green light measurement, [F o G (2) ]c / [F o G (2) ]t=[γ G ]c / [γ G ]t*[Fo G ]c / [F o G ]t Under blue light measurement, [F o B ]c / [F o B ]t≈[F o B (2) c / F o B (2) ]t≈[F o G (2) ]c / [F o G (2) ]t Combining the two formulas above, we obtain [γ] G Formula for calculating t [γ G ]t=[F o G ]c / [F o G ]t*[F o B ]t / [F o B ]c*[γ G c-type V Note: c represents the tomato leaf of the normal control group, and t represents the tomato leaf of the test group.

[0042] Under dark adaptation conditions, with the PSII reaction center fully open (F o Under the specified measurement conditions, relevant parameters were set based on the fluorescence contribution patterns of PSI and PSII due to their inherent differences in spectral absorption characteristics. According to the studies by Pfündel (2009) and Lichtenthaler (2021): in the blue light band (450-500 nm), the light-harvesting complex (LHC II) of PSII contributes the vast majority of fluorescence due to its efficient absorption of excitation light, while the contribution of PSI is minimal and negligible; in the green light band (500-550 nm), although the contribution of PSII is still dominant, its proportion decreases due to its reduced absorption efficiency, while the contribution of PSI is relatively increased due to the specific absorption of carotenoids.

[0043] Based on this, the excitation light ratio factor [γ] for tomato leaves in the normal control group was set. G c is a fixed value of 0.7. Finally, the photochemical efficiency Φ of photosystem I is calculated according to equations III, IV, and V. PSI .

[0044] Example 2, Photochemical Efficiency (Φ) of Photosystem I (PSI) PSI Application verification The test material was a wild-type tomato variety (Condine Red). Seeds were soaked and then germinated in a constant-temperature shaker (28℃, 200 rpm / min). When the radicle length was 0.5–1 cm, they were sown in seed trays. The substrate consisted of imported peat moss and vermiculite (3:1, v / v). The plants were cultured in a plant factory with a 12 h / 12 ​​h photoperiod, an average day / night temperature of 25℃ / 20℃, and a light intensity of 200 μmol / m³. -2 s -1 Once the seedlings have grown to the stage of three leaves and one bud, select seedlings with uniform growth and transplant them into seedling pots with a diameter of 10 cm, and continue to cultivate them until they have six leaves and one bud.

[0045] Tomatoes with good and uniform growth were selected and divided into four groups. Three groups underwent low-temperature treatment, high-temperature treatment, and drought treatment, respectively. The other group served as a control and grew normally in a climate chamber with a photoperiod of 12 h / 12 ​​h, an average day / night temperature of 25℃, and a light intensity of 200 μmol / m². -2 s -1 .

[0046] High temperature treatment: Place the tomato plants in a plant climate chamber, set the temperature to 35℃, and test after 48 hours; Drought treatment: Tomato plants were placed in a plant climate chamber and left unwatered for 7 days before testing. Low temperature treatment: Tomato plants were placed in a plant climate chamber and the temperature was set to 4℃. The results were taken after 48 hours. Control treatment: Tomato plants were placed in a plant climate chamber at a temperature of 25℃ and a light intensity of 200 μmol / m². -2 s -1 Test to be performed after 48 hours.

[0047] It should be noted that, in each stress treatment, all environmental factors except the stress factor were the same as those in the control group.

[0048] Take out each group of tomatoes to be tested in turn, turn on the Mini-PAM fluorometer, adjust the test light to blue light or green light respectively, take out each group of tomatoes to be tested in turn, measure the leaves and record the data, and turn off the instrument after the test.

[0049] The operation method of the Mini-PAM chlorophyll fluorometer is as follows: Install the instrument, connect it to the computer, and launch the operating software. Switch to the "Image" interface and configure the settings in the "Setting" module at the bottom right. First, use blue light as the measurement light: at this time, all green LEDs are off. The pulse width of the blue light measurement light is 42 μs, and the frequency is 8 Hz. The saturation light pulse width is 100 μs, and the frequency is 8000 Hz. Switch to the "Kinetics" interface and click the "Start" button in the bottom right corner to begin the measurement. After the measurement is complete, click the "Stop" button to stop the measurement. Switch to the "Report" interface to record the data. In darkness, the blue light measurement light excites the initial fluorescence F in the leaf. o B The maximum fluorescence F produced by photoexcited leaves was measured under saturated light. m B Next, use the green light measurement mode: In this mode, all blue LEDs are off. The green light measurement mode is essentially the same as the blue light mode. The initial fluorescence and maximum fluorescence generated by green light photoexcitation are measured at F0 and F1, respectively. o G F m G Blue light has a wavelength of 450nm, and green light has a wavelength of 520nm.

[0050] After data collection, the data was saved to an Excel spreadsheet. A control group of plants [γ] was set up. G c=0.7, and the [γ] of the test group plants was calculated according to formula V in Example 1. G ]t, and then the photochemical efficiency Φ of photosystem I is calculated according to Equations III and IV. PSI .

[0051] Box plots were created using GraphPad Prism 8 software, and the rate of decline was calculated using the formula: Rate of Decline = (Mean of Control Group) / (Mean of Control Group) (Mean value of treatment group) / Mean value of control group × 100%. The photochemical efficiency Φ of the photosystem I of the tomato leaves under test was observed by the decrease ratio. PSI Whether it was significantly lower than the control group. Specific results are as follows: In this experiment, the photochemical efficiency Φ of the photosystem I in the tomato leaves of the control group was... PSI The average value was 0.692. The decrease rate was calculated to observe the Φ of the leaves of the tomato plants being tested. PSI Whether it is significantly lower than the control group: If the decrease rate reaches 15%, it is diagnosed that the tested plant is under stress and its physiological state has deteriorated; for example, the photochemical efficiency Φ of photosystem I in the high temperature group. PSI The mean value is 0.650, and the drought group Φ PSI The mean value is 0.654, and the Φ value of the low temperature group is... PSI The mean was 0.522, and their decrease rates were 15.73%, 15.18%, and 32.36%, respectively. Figure 3 The decrease rate in all three test groups exceeded 15%, indicating that the Φ of these three test groups... PSI All of these values ​​were significantly lower than those of the control group. Therefore, it can be concluded that the tomato plants tested after high temperature, drought and low temperature treatments in this invention were affected by stress, and the greater the decrease rate, the greater the degree of stress and the worse the physiological state.

[0052] Comparative Example 1 This example aims to verify the photochemical efficiency (Φ) of the optical system I constructed in this invention. PSI Compared to the traditional chlorophyll fluorescence parameter F v B / F m B The PSII maximum photochemical efficiency is more sensitive in reflecting plant responses to abiotic stress.

[0053] The experimental materials and processing were exactly the same as in Example 2. The F values ​​were directly measured using a Mini-PAM fluorescence spectrometer in blue light measurement mode. o B and F m B Calculate the maximum photochemical efficiency parameter F of traditional PSII v B / F m B =(F m B -F o B ) / F m B Box plots were created using GraphPadPrism 8 software to calculate the rate of decrease in traditional chlorophyll fluorescence parameters under different stress treatments, and to assess their sensitivity. The rate of decrease was calculated as follows: (mean value of control group) (Mean of treatment group) / Mean of control group × 100%.

[0054] Table 1 Group <![CDATA[Instrument measures F v B / F m B > <![CDATA[F v B / F m B Decline rate <![CDATA[Φ PSI Mean <![CDATA[Φ PSI Decline rate control group 0.741 / 0.772 / High temperature group 0.716 2.89% 0.650 15.73% drought group 0.721 2.73% 0.654 15.18% Low temperature group 0.615 17.04% 0.522 32.36% like Figure 4 As shown in Table 1, under the same stress conditions, the photochemical efficiency Φ of photosystem I is... PSI The value is higher than that of F obtained directly by the instrument. v B / F m B More sensitive. Φ PSI The decrease was significantly greater than that of F. v B / F m B The magnitude of the decrease indicates that Φ PSIThe response to abiotic stress is more sensitive. Using traditional thresholds (high temperature, drought treatment), it might be difficult to determine that the plant is under significant stress; however, Φ... PSI The decline rate was over 15%, which can reflect the deterioration of the plant's physiological state earlier and more accurately.

[0055] Photosystem I is more susceptible to irreversible damage than photosystem II under environmental stress. However, traditional chlorophyll fluorescence measurement methods cannot accurately reflect the function of photosystem I and are not very effective in determining whether plants are under stress, especially in the early stages of stress. This invention proposes a method that uses blue and green light as excitation light to detect and optimize existing calculation formulas to determine the physiological state of crops. The calculated photochemical efficiency Φ of photosystem I is... PSI It is more sensitive to stress, which can improve the accuracy of judgment. In the future, it is expected to enable producers to detect and intervene in crops in the early stages of stress, significantly improving crop yield and quality.

[0056] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for calculating the photochemical efficiency Φ of a leaf photosystem I PSI The method is characterized by, Includes the following steps: S1. Illuminate the leaf under test using the blue and green light measuring lights of the measuring instrument, and detect and record the initial fluorescence F generated by blue light excitation. o B and maximum fluorescence F m B The initial fluorescence F generated by green light excitation o G and maximum fluorescence F m G ; S2. Calculate the photochemical efficiency Φ of photosystem I using the following formula. PSI ; The photochemical efficiency Φ of the optical system I PSI The calculation formula is: (I)Φ PSI =1-1 / k1 (II) (III) In the above formula (I), k1 refers to the photosynthetic parameters of optical system I; In the formula (II), γ G For measuring the effect of PSII on initial fluorescence F under green light o G The contribution coefficient; In the aforementioned formula (III), F o G (c) and F o B (c) The initial fluorescence of the control group leaves under green and blue light measurement, respectively. o G (t) and F o B (t) represents the initial fluorescence of the leaf under green and blue light measurement, respectively, γ G (c) is the contribution coefficient of PSII to the initial fluorescence of the control group leaves under green light measurement; The control group consisted of leaves from healthy plants under normal growth conditions. The main peak of the blue light measurement light is 440~470 nm, and the main peak of the green light measurement light is 510~530 nm.

2. The method according to claim 1, characterized in that, The γ G (c) Set to 0.

7.

3. The method according to claim 1, characterized in that, The blade to be tested underwent a dark adaptation treatment for at least 30 minutes before measurement.

4. The method according to any one of claims 1 to 3, characterized in that, Both the test leaves and the control group leaves were mature, functional leaves.

5. The method according to claim 1, characterized in that, The pulse width of the blue light measurement light and the green light measurement light are 30~50 μs and the frequency is 5~15 Hz.

6. The method according to claim 1, characterized in that, The saturation pulse width used to measure maximum fluorescence is 80~120 μs, and the frequency is 6000~10000 Hz.

7. A method for determining whether a plant is suffering from environmental stress using the method described in any one of claims 1 to 6, characterized in that, include: The Φ of the plant leaf to be tested PSI Φ value compared to control group leaves PSI Compare the values, if Φ PSI If the value decreases by no less than 15%, the plant is considered to be under environmental stress.

8. The method according to claim 7, characterized in that, The environmental stress is selected from at least one of the following: drought stress, salinity stress, low temperature stress, high temperature stress, and low light stress.

9. The method according to claim 7, characterized in that, The plant mentioned includes: tomato.

Images