阅读说明：本技术 农作物生理和结构表型参数多任务并行的自动观测方法 (Automatic multi-task parallel observation method for physiological and structural phenotypic parameters of crops ) 是由 张永光 张乾 吴霖升 张小康 金时超 吴云飞 于 2021-08-31 设计创作，主要内容包括：本申请公开了农作物生理和结构表型参数多任务并行的自动观测方法,包括：搭建光谱观测系统并对其进行辐射定标,得到辐射定标系数；根据辐射定标后的光谱观测系统,对太阳入射光谱和不同点位的农作物冠层反射光谱进行连续观测,得到时序光谱观测数据；根据辐射定标系数对光谱观测数据进行数据处理,得到太阳入射光谱和不同点位的农作物冠层反射光谱的辐亮度值；根据太阳入射光谱和不同点位的农作物冠层反射光谱的辐亮度值,并行反演各观测对象的生理和结构时序表型参数。本申请能够并行获取太阳入射光谱和不同点位的农作物冠层反射光谱,并反演得到不同点位的农作物冠层的生理和结构时序表型参数。(The application discloses a crop physiological and structural phenotype parameter multi-task parallel automatic observation method, which comprises the following steps: a spectral observation system is built and subjected to radiometric calibration to obtain a radiometric calibration coefficient; continuously observing a solar incident spectrum and crop canopy reflection spectra at different point positions according to the spectrum observation system after radiometric calibration to obtain time sequence spectrum observation data; performing data processing on the spectral observation data according to the radiometric calibration coefficient to obtain the radiance values of the solar incident spectrum and the crop canopy reflection spectrum at different points; and according to the solar incident spectrum and the radiance values of the crop canopy reflection spectra at different point positions, inverting physiological and structural time sequence phenotype parameters of each observation object in parallel. According to the method and the device, the solar incident spectrum and the crop canopy reflection spectrum at different point positions can be obtained in parallel, and the physiological and structural time sequence phenotype parameters of the crop canopy at different point positions are obtained through inversion.)

1. The method for automatically observing physiological and structural phenotypic parameters of crops in a multitask parallel mode is characterized by comprising the following steps:

a spectrum observation system is built, and radiometric calibration is carried out on the spectrum observation system to obtain a radiometric calibration coefficient; the spectrum observation system comprises a spectrometer and a multi-optical multiplexer which are connected in sequence; the spectrometer only comprises one optical path inlet and is connected with an outlet of the multi-optical multiplexer through a single-core optical fiber, the multi-optical multiplexer comprises a plurality of parallel optical path inlets, and in the observation process, the multi-optical multiplexer only opens one optical path inlet; each optical path inlet of the multi-optical multiplexer is provided with an optical fiber with a preset length, and one end of the optical fiber is connected with the optical path inlet of the multi-optical multiplexer; the other end of one of the optical fibers is connected with a cosine corrector, and the cosine corrector is vertically and upwards installed and used for collecting the incident spectrum of the sun; the rest light path channels of the multi-optical multiplexer are respectively used for acquiring the crop canopy reflection spectrums at different point positions;

aiming at each observation object, firstly collecting a solar incident spectrum, then switching the multi-optical multiplexer to a light path channel of a canopy reflection spectrum of the corresponding observation object, collecting the canopy reflection spectrum, and alternately completing data collection of the solar incident spectrum and the canopy reflection spectrum of each observation object to obtain time sequence spectrum observation data; in the observation process, optimizing the spectrometer integration time of the spectrum observation system, observing the solar incident spectrum and the crop canopy reflection spectrum at different points by the spectrum observation system according to the optimized spectrometer integration time, and collecting dark current data corresponding to the spectrometer integration time;

performing data processing on the spectrum observation data according to the radiometric calibration coefficient and the dark current data to obtain a solar incident spectrum and radiance values of crop canopy reflection spectra at different point positions;

and according to the solar incident spectrum and the radiance values of the crop canopy reflection spectra at different point positions, inverting physiological and structural time sequence phenotype parameters of each observation object in parallel.

2. The method for the multitask and parallel automatic observation of physiological and structural phenotypic parameters of crops according to claim 1, characterized in that the physiological and structural time sequence phenotypic parameters of each observed object are obtained by obtaining the canopy reflection spectra of different observed objects in parallel; the inversion of the physiological parameters includes fluorescence inversion; the fluorescence inversion comprises the following steps: and (3) inverting the fluorescence F by adopting a spectrum fitting method, expressing rho and F by using a polynomial model, and expressing the radiance L reflected by the canopy as follows:

where rho_MOD(lambda) and F_MOD(λ) is a mathematical expression of reflectance and fluorescence in the respective wavelength bands, L_TOC(λ) represents the radiance of the observed canopy reflectance spectrum, E (λ) is the radiance of the solar incident spectrum, and ∈ (λ) represents the residual term of the observed and fitted values for each band; solving a linear equation set through least squares to obtain rho_MOD(lambda) and F_MOD(λ), thereby calculating F and ρ;

the structural parameter inversion comprises vegetation reflectance index inversion, the vegetation reflectance index comprising a normalized vegetation index NDVI, a vegetation near-infrared index NIRv, a ratio vegetation index RVI, a wide dynamic range vegetation index WDRVI, a MERIS terrestrial chlorophyll index MTCI; NDVI, NIRv, RVI, WDRVI, MTCI were calculated as follows:

in the formula, ρ_nir、ρ_red、ρ_735.75、ρ_708.75、ρ_681.25The reflectivities are respectively near infrared waveband, red light waveband, 735.75nm wavelength, 708.75nm wavelength and 681.25nm wavelength; α is a coefficient to reduce the near infrared contribution.

Technical Field

The application relates to the technical field of vegetation remote sensing parameter acquisition, in particular to a multi-point crop physiological and structural phenotype parameter multi-task parallel automatic observation method.

Background

The plant phenotype is an important bridge for researching the interaction between plant genes and the environment, is a core means for serving crop genetic breeding and cultivation management, and has vital strategic significance for guaranteeing germplasm resources and food safety. High-throughput structural and physiological phenotypic monitoring of crops is a hotspot of current research in the process of achieving the goals of high yield, high quality, high resistance and the like of crops. At present, the acquisition means of the crop structural phenotype is relatively mature, but the method for carrying out time sequence observation on the crop structural phenotype is relatively deficient, and the biological significance of most structural traits needs to be further explored. Meanwhile, the monitoring of the physiological phenotype of the crops is in an early stage, synchronous observation with the structural phenotype is not realized, and the requirements of comprehensive monitoring, management and screening of target characters in the growth and development processes of the crops are difficult to meet. Therefore, there is a need for an automatic observation method capable of simultaneously obtaining physiological and structural phenotypic parameters of crops to meet the research requirement of high-throughput plant phenotype.

The sunlight induced chlorophyll fluorescence (hereinafter referred to as fluorescence) is a spectral signal (650-800nm) emitted by a plant photosynthesis center, can reflect the photosynthesis state of vegetation, is known as a probe of plant photosynthesis, and provides a new idea and method for excavating crop structures with biological significance and estimating physiological phenotypes. There are three directions for the absorbed light energy to be implanted, photosynthesis, heat dissipation and fluorescence respectively. The energy used by vegetation for photosynthesis is less than 20% of the light energy absorbed, while most of the energy is released by heat dissipation and a small part of the energy is released by fluorescence. Because the three energies are closely related, the trade-off relationship exists, and therefore under the condition that the solar radiation energy is absorbed for a certain time, the related information such as photosynthesis and the like of the vegetation can be detected more directly by observing fluorescence. Compared with the traditional vegetation index, the fluorescence can reflect the photosynthetic dynamic change of vegetation, so that the method is full of potential in the field of crop physiological phenotype monitoring.

The basic principle and imaging system of the chlorophyll fluorescence technology and the analysis and processing method of the chlorophyll fluorescence parameters are introduced in the research progress of the chlorophyll fluorescence technology in plant phenotype analysis, such as Asterina sieboldii and the like, and the application of the sunlight-induced chlorophyll fluorescence technology in the aspects of plant abiotic stress analysis, biotic stress analysis, excellent character screening and the like is summarized. Because photosynthesis of plants is changed under stress, chlorophyll fluorescence is widely used in abiotic stresses such as drought, temperature and salt stresses, and biotic stresses caused by viruses, bacteria and fungi. Due to the rapid response and accurate indication of chlorophyll fluorescence to photosynthesis change, the method is also widely applied to screening of new crop varieties which are tolerant to environment and have high yield and high quality.

At present, the application of chlorophyll fluorescence technology in the field of plant phenotype is mainly active chlorophyll fluorescence, and dark adaptation, long period, small scale and field measurement difficulty exist. In contrast, sunlight-induced chlorophyll fluorescence has the advantages of being rapid, multi-scale, and easy to measure in the field, facilitating better acquisition of physiological phenotypes associated with photosynthesis and stress. However, time-series high-throughput physiological and structural phenotypic monitoring requires an automated, stable fluorescence observation system. Therefore, there is a need for a method for automatic observation of physiological and structural phenotypic parameters of crops in a multitask parallel manner.

Disclosure of Invention

The application aims to provide a crop physiological and structural phenotype parameter multi-task parallel automatic observation method, so that the problems in the prior art are solved, a solar incident spectrum and crop canopy reflection spectra at different point positions can be obtained in parallel, and physiological and structural time sequence phenotype parameters of crop canopies at different point positions are obtained through inversion.

Simultaneously, the incident spectrum of the sun and the reflection spectrum of the canopy of the crop at different point positions are obtained in parallel, and the parallel inversion of the physiological and structural phenotype parameters of the crop is completed through the reflection spectrum.

In order to achieve the above purpose, the present application provides the following solutions: the application provides a crop physiological and structural phenotype parameter multi-task parallel automatic observation method, which comprises the following steps:

a spectrum observation system is built, and radiometric calibration is carried out on the spectrum observation system to obtain a radiometric calibration coefficient; the spectrum observation system comprises a spectrometer and a multi-optical multiplexer which are connected in sequence; the spectrometer only comprises one optical path inlet and is connected with an outlet of the multi-optical multiplexer through a single-core optical fiber, the multi-optical multiplexer comprises a plurality of parallel optical path inlets, and in the observation process, the multi-optical multiplexer only opens one optical path inlet; each optical path inlet of the multi-optical multiplexer is provided with an optical fiber with a preset length, and one end of the optical fiber is connected with the optical path inlet of the multi-optical multiplexer; the other end of one of the optical fibers is connected with a cosine corrector, and the cosine corrector is vertically and upwards installed and used for collecting the incident spectrum of the sun; the rest light path channels of the multi-optical multiplexer are respectively used for acquiring the crop canopy reflection spectrums at different point positions;

aiming at each observation object, firstly collecting a solar incident spectrum, then switching the multi-optical multiplexer to a light path channel of a canopy reflection spectrum of the corresponding observation object, collecting the canopy reflection spectrum, and alternately completing data collection of the solar incident spectrum and the canopy reflection spectrum of each observation object to obtain time sequence spectrum observation data; in the observation process, optimizing the spectrometer integration time of the spectrum observation system, observing the solar incident spectrum and the crop canopy reflection spectrum at different points by the spectrum observation system according to the optimized spectrometer integration time, and collecting dark current data corresponding to the spectrometer integration time;

performing data processing on the spectrum observation data according to the radiometric calibration coefficient and the dark current data to obtain a solar incident spectrum and radiance values of crop canopy reflection spectra at different point positions;

and according to the solar incident spectrum and the radiance values of the crop canopy reflection spectra at different point positions, inverting physiological and structural time sequence phenotype parameters of each observation object in parallel.

Optionally, acquiring the canopy reflection spectra of different observation objects in parallel, and performing inversion to acquire physiological and structural time sequence phenotype parameters of each observation object; the inversion of the physiological parameters includes fluorescence inversion; the fluorescence inversion comprises the following steps: and (3) inverting the fluorescence F by adopting a spectrum fitting method, expressing rho and F by using a polynomial model, and expressing the radiance L reflected by the canopy as follows:

where rho_MOD(lambda) and F_MOD(λ) is a mathematical expression of reflectance and fluorescence in the respective wavelength bands, L_TOC(λ) represents the radiance of the observed canopy reflectance spectrum, E (λ) is the radiance of the solar incident spectrum, and ∈ (λ) represents the residual term of the observed and fitted values for each band; solving a linear equation set through least squares to obtain rho_MOD(lambda) and F_MOD(λ), thereby calculating F and ρ;

the structural parameter inversion comprises vegetation reflectance index inversion, the vegetation reflectance index comprising a normalized vegetation index NDVI, a vegetation near-infrared index NIRv, a ratio vegetation index RVI, a wide dynamic range vegetation index WDRVI, a MERIS terrestrial chlorophyll index MTCI; NDVI, NIRv, RVI, WDRVI, MTCI were calculated as follows:

in the formula, ρ_nir、ρ_red、ρ_735.75、ρ_708.75、ρ_681.25The reflectivities are respectively near infrared waveband, red light waveband, 735.75nm wavelength, 708.75nm wavelength and 681.25nm wavelength; α is a coefficient to reduce the near infrared contribution.

The application discloses following technological effect:

the application provides a multi-task parallel automatic observation method for physiological and structural phenotype parameters of crops, which utilizes an automatic hyperspectral observation system to obtain high-flux spectral data of crops according to time sequence and provides a method for continuously inverting the phenotype parameters of crop canopies. According to the method, the solar incident spectrum and the canopy reflection spectrum are alternately acquired through the multiple optical multiplexer, and simultaneously, the spectrum data of all the observation objects are acquired in parallel in one observation cycle, so that the automatic periodic observation of multiple targets is guaranteed to be completed in a short time, the artificial interference of observation behaviors on the observation targets and the time difference in the observation period of the multiple targets are reduced, and the high-flux structure and the physiological phenotype of a time sequence can be obtained. Comprehensive cognition of the growth vigor of crops under different environmental conditions can be improved by fusing the structure and the physiological phenotype parameters, the character difference of the variety in different growth stages can be further deeply excavated through time sequence observation, the crop cultivation and breeding can be better assisted, the accurate regulation of timely monitoring and management measures of crop cultivators on the agricultural condition (photosynthesis and adversity physiology) is facilitated, the novel character of the crop key growth stage is beneficially excavated by genetic breeders, and the variety improvement is realized; has important significance for solving the safety problems of the prior provenance neck clamp and the grain.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for a person skilled in the art to obtain other drawings without any inventive exercise.

FIG. 1 is a flow chart of a method for multitasking and parallel automatic observation of physiological and structural phenotypic parameters of crops according to an embodiment of the present application;

FIG. 2 is a schematic structural diagram of a spectrum observation system in an embodiment of the present application;

FIG. 3 is a schematic diagram of a radiometric calibration system according to an embodiment of the present application;

FIG. 4 is a diagram illustrating reflectivity of each cell in the embodiment of the present application;

FIG. 5(a) is a graph showing seasonal variations in phenotypic physiological parameters (for example, far-red SIF and red-band SIF) of different experimental groups and control groups in an example of the present invention;

FIG. 5(b) is a graph showing the daily dynamic of the phenotypic physiological parameters (for example, far-red SIF and red-band SIF) of different experimental groups and control groups in the examples of the present invention;

FIG. 6(a) is a graph showing seasonal variations in phenotypic structural parameters (for example, NDVI and NIRv) of different experimental and control groups in examples of the present invention;

FIG. 6(b) is a graph showing the daily dynamic of the phenotypic structural parameters (NDVI and NIRv as examples) of the different experimental and control groups in the examples of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.

It should be noted that the steps illustrated in the flowcharts of the figures may be performed in a computer system such as a set of computer-executable instructions and that, although a logical order is illustrated in the flowcharts, in some cases, the steps illustrated or described may be performed in an order different than presented herein.

Referring to fig. 1, the present embodiment provides a method for multi-task parallel automatic observation of physiological and structural phenotypic parameters of crops, comprising:

s101, building a spectrum observation system, and carrying out radiometric calibration on the spectrum observation system to obtain a radiometric calibration coefficient;

in the step, a spectrum observation system is used for observing a solar incident spectrum and crop canopy reflection spectra at different point positions and performing phenotype parameter inversion on crops according to a spectrum observation result; the spectrum observation system comprises a spectrometer and a multi-optical multiplexer.

The spectrometer is used for observing the incident spectrum of the sun and the reflection spectrum of the canopy of the crops at different point positions; the spectrometer only comprises one optical path inlet, and the optical path inlet of the spectrometer is connected with the outlet of the multi-optical multiplexer through a single-core optical fiber; the spectrometer is sealed in the temperature control box, a cooling device is arranged in the temperature control box, and the temperature control box is installed in the portable sealing box, so that the waterproof and sun-proof effects of field installation and use are guaranteed. The model of the spectrometer and the temperature reduction equipment can be selected according to actual conditions, for example, in the embodiment, the spectrometer adopts an ultrahigh spectral resolution spectrometer manufactured by Ocean inertia company in the U.S. A, the model is a QEPOR spectrometer, the spectral range is 650 plus 800nm, the spectral resolution is 0.3nm, and the spectrometer is connected with a computer through a USB interface to transmit signals. An optical path switch is arranged in the spectrometer and can control whether external light can enter the spectrometer or not, and the default state is an open state. The cooling equipment adopts TEC cooling equipment, and the temperature control box is set to be 25 ℃, so that the overhigh ambient temperature is avoided.

The multi-optical multiplexer is used for alternately acquiring the solar incident spectrum and the crop canopy reflection spectrum at different point positions and transmitting the acquired solar incident spectrum and the crop canopy reflection spectrum to the spectrograph; the multi-optical multiplexer comprises a plurality of parallel optical path inlets, and only one optical path inlet is opened by the multi-optical multiplexer during observation so as to ensure the uniqueness of light entering the spectrometer; and a plurality of parallel light path channels of the multi-optical multiplexer are respectively used for acquiring a solar incident spectrum and crop canopy reflection spectra at different point positions. The type of the optical multiplexer can be selected according to actual conditions, for example, in the embodiment, the optical multiplexer is a type MPM-2000 optical multiplexer manufactured by Ocean inertia corporation in usa, and the optical multiplexer includes 16 optical path inlets.

Each optical path inlet of the multi-optical multiplexer is provided with an optical fiber with a preset length, and one end of the optical fiber is connected with the optical path inlet of the multi-optical multiplexer; the other end of one optical fiber in each optical fiber is connected with a cosine corrector, the cosine corrector is vertically installed upwards and used for collecting solar incident spectrums, and the rest light path inlets of the multiple optical multiplexers are respectively used for obtaining crop canopy reflection spectrums at different point positions, so that spectrum observation can be carried out on a plurality of cells at the same time. When the field appearance is measured, each light path inlet of the multi-optical multiplexer is assembled with an optical fiber with proper length according to the position of an observation target, the model of the cosine corrector is CC-3, and the corresponding cosine corrector on the light path channel for observing the incident spectrum of the sun is vertically installed upwards; the optical fiber corresponding to the optical path channel for observing the canopy reflection spectrum of the crops is vertically installed downwards. The spectrometer and the multi-optical multiplexer are connected to a microcomputer through a USB connecting line, and the microcomputer controls the operation, the optical path switching and the data acquisition and storage of the spectrometer and the multi-optical multiplexer through programs.

The precision of parameter comparison between different observation targets can be influenced by slight difference of optical characteristics caused by the length of each optical path optical fiber and the manufacturing process, and each optical path channel of the multi-optical multiplexer needs to be subjected to unified radiation calibration before field installation. In the embodiment, a radiometric calibration system is used for radiometric calibration of the spectrum observation system to obtain a radiometric calibration coefficient; the radiometric calibration system comprises a first radiometric calibration device and a second radiometric calibration device; the first radiometric calibration device is used for radiometric calibration of bare fibers (fibers in the multi-optical multiplexer for acquiring crop canopy reflection spectra at different points); the second radiometric calibration device is used for radiometric calibration of the optical fiber (the optical fiber for collecting the solar incident spectrum in the multi-optical multiplexer) provided with the cosine corrector; the first radiometric calibration device and the second radiometric calibration device have various types, for example, in this embodiment, the first radiometric calibration device employs an integrating sphere, and optionally, the integrating sphere is a 50-inch diffuse reflection integrating sphere; the method for radiometric calibration of the bare optical fiber comprises the following steps: and (3) utilizing a 50-inch diffuse reflection integrating sphere with stable light intensity to perform radiation calibration on the light path channels of each multi-optical multiplexer in a darkroom, fixing the tail ends of the optical fibers connected to each light path channel at a light outlet of the integrating sphere, measuring to obtain a recorded value (recorded value of a spectrometer) without physical significance, and converting into a first radiation calibration coefficient of the bare optical fiber in each light path channel according to the radiance of the integrating sphere. The second radiation scaling device adopts a halogen lamp, and optionally, the halogen lamp adopts HL-3 halogen lamp produced by Ocean inertia company in America; the method for radiometric calibration of the optical fiber provided with the cosine corrector comprises the following steps: and inserting the optical fibers connected to each optical path channel into the halogen lamp, measuring a recorded value (recorded value of a spectrometer) without physical significance, and converting the recorded value into a second radiometric scaling coefficient of the optical fiber provided with the cosine corrector in each optical path channel according to the radiance of the halogen lamp.

The recorded value of each light path obtained by field observation is multiplied by the scaling coefficient of the corresponding light path to be converted into radiance with physical significance, and the difference caused by the optical characteristics of each light path is eliminated. In addition, as an alternative, a portable small integrating sphere can be used in the field for radiometric calibration of bare fiber, while fiber equipped with a cosine corrector can also be calibrated using an HL-3 halogen lamp.

S102, continuously observing a solar incident spectrum and crop canopy reflection spectra at different point positions according to the spectrum observation system after radiometric calibration to obtain time sequence spectrum observation data;

in the step, the software of the spectrum observation system is compiled by C # language, and a simple visual operation interface is provided. The program mainly comprises the initialization of a spectrometer, the integration time optimization of the spectrometer, the light path switching, the scanning of the spectrometer, the data acquisition, the data storage, the inversion of phenotypic parameters and the like.

The initial integration time of the spectrometer is set by initialization of the spectrometer.

Due to the uncertainty of field weather and the limited recording numerical range of the spectrograph, in order to achieve the optimal detection effect of the spectrograph, the recorded data are not too small or saturated, the integral time of the collected spectrum is automatically adjusted through the change of the spectrum intensity, and the spectrum observation system observes the solar incident spectrum and the crop canopy reflection spectrum at different points according to the optimization result of the integral time of the spectrograph, so that the collected spectrum signals are accurate and effective. The calculation formula is as follows:

T＝IT×targetDN/max (1)

wherein, T is the optimized spectrometer integration time, IT is the user-defined initial integration time, targetDN is the user-defined ideal spectrometer record value, and max is the spectrometer record value with the maximum spectrum collected in the user-defined initial integration time IT. And setting the maximum integration time for the spectrum observation system, and recording whether the recorded value reaches an ideal state or not when the integration time reaches the maximum integration time so as to prevent the infinite integration time.

The spectral observation data obtained by observing the incident spectrum of the sun and the reflection spectrum of the canopy of the crops at different point positions in time comprises: the dark current in the spectrometer integration time corresponding to the solar incident spectrum, the crop canopy reflection spectrum at different point positions, the solar incident spectrum and the crop canopy reflection spectrum at different point positions. The specific process of observation is as follows:

the method comprises the steps that a multi-optical multiplexer is switched to an optical path channel for observing a solar incident spectrum, a solar incident spectrum is collected according to the initial integration time of a spectrometer, the integration time after the optimization of the spectrometer is calculated by using a formula (1), then a solar incident spectrum is observed according to the optimized integration time and data is recorded, then an internal optical path switch of the spectrometer is closed, and a dark current is recorded according to the optimized integration time, namely noise data generated by the spectrometer when no light enters the spectrometer is generated; and then the multi-optical multiplexer is switched to a first optical path channel for observing the crop canopy reflection spectrum, and the steps are repeated to obtain the crop canopy reflection spectrum and the corresponding dark current. And sequentially measuring all crop observation targets in a round according to the process, and finishing an observation cycle every hour. Each solar incident spectrum and canopy reflection spectrum obtained in the observation process are recorded in a CSV file, and corresponding information such as integration time, dark current and the like is recorded at the same time.

S103, performing data processing on the spectrum observation data according to the radiometric calibration coefficient to obtain the radiance values of the solar incident spectrum and the crop canopy reflection spectrum at different points, and calculating to obtain corresponding reflectivity;

in this step, the data processing method includes: firstly, respectively subtracting corresponding dark current from a solar incident spectrum and crop canopy reflection spectra at different point positions so as to eliminate the noise of the instrument; secondly, respectively dividing the solar incident spectrum and the crop canopy reflection spectrum after subtracting the dark current by corresponding integration time; wherein the integration time is normalized to 1 second; thirdly, multiplying the incident solar spectrum and the crop canopy reflection spectrum which are divided by the integration time by the radiometric calibration coefficient of the corresponding light path to obtain the radiance values of the incident solar spectrum and the crop canopy reflection spectrum at different points; finally, dividing the radiance values of the crop canopy reflection spectra at different point positions by the radiance values of the sunlight incidence spectra to obtain the reflectivities of crops at different point positions; the reflectivity of the crop at different points is used to perform the inversion of the crop phenotypic parameters. The spectral data and reflectance are stored on a computer.

And S104, parallelly inverting physiological and structural time sequence phenotype parameters of each observation object according to the solar incident spectrum and the radiance values of the crop canopy reflection spectra at different points.

In the step, physiological and structural time sequence phenotype parameters of each observation object are obtained through parallel acquisition of canopy reflection spectra of different observation objects; the inversion of the physiological parameters comprises fluorescence inversion, an oxygen absorption well exists in solar radiation at about 760nm, a spectrum curve is in a concave state, fluorescence is emitted outwards by plants and can be filled in the absorption well, and canopy fluorescence can be obtained by inversion extraction by comparing the relative intensity of radiance of a dark line of the absorption well of a solar incident spectrum and a canopy reflection spectrum of crops and adjacent wave bands of the absorption well; the method specifically comprises the following steps: the canopy reflection at the dark line consists of real reflection rho and fluorescence F of the canopy, the fluorescence F is inverted by adopting a spectrum fitting method, the rho and the F can be expressed by a polynomial model, and the radiance L of the canopy reflection is expressed as:

where rho_MOD(lambda) and F_MOD(λ) are mathematical expressions for the reflectance and fluorescence, respectively, in the respective wavelength bands (wavelength of the band is in), L_TOC(λ) represents the radiance of the observed canopy reflectance spectrum, E (λ) is the radiance of the solar incident spectrum, and ε (λ) represents the residual term of each band observation and fit. By solving the linear equation system with least squares, ρ can be obtained_MOD(lambda) and F_MOD(λ), thereby calculating F and ρ.

The spectrum observation system can obtain high-flux hyperspectral reflectivity data within the range of 650-800nm, and the hyperspectral reflectivity data can be used for calculating various vegetation reflectivity indexes related to plant canopy structures, such as normalized vegetation index (NDVI), vegetation near infrared index (NIRv), Ratio Vegetation Index (RVI), wide dynamic range vegetation index (wdi), MERIS land chlorophyll index (MTCI), and the like, and is specifically shown in table 1:

TABLE 1

In Table 1,. rho_nir、ρ_red、ρ_735.75、ρ_708.75、ρ_681.25The reflectivities are respectively near infrared waveband, red light waveband, 735.75nm wavelength, 708.75nm wavelength and 681.25nm wavelength; α is a coefficient to reduce the near infrared contribution.

The following describes the observation method and system of the present invention in detail by a preferred embodiment:

s201, installing a spectrum observation system according to the structure diagram of the figure 2;

s202, carrying out radiometric calibration on the spectrum observation system according to the graph 3; wherein, after being installed in the field, the field radiometric calibration is required to be carried out regularly; the optical fiber for measuring the incident spectrum of the sun is provided with a cosine corrector and is vertically installed upwards, and the optical fibers for measuring the reflection spectrum of the canopy of crops are aligned to the central position of each cell and are vertically installed downwards.

S203, optimizing the integration time of the spectrometer by adopting an integration time optimization algorithm, and automatically acquiring a solar incident spectrum, crop canopy reflection spectra at different point positions and dark current corresponding to the integration time; the spectrum is collected when the solar altitude is larger than 0 degree every day, and the operation is stopped when the solar altitude is smaller than 0 degree.

S204, subtracting corresponding dark current from the solar incident spectrum and the crop canopy reflection spectrum at different point positions respectively, and dividing the solar incident spectrum and the crop canopy reflection spectrum after subtracting the dark current by corresponding integration time respectively; wherein the integration time is normalized to 1 second; multiplying the solar incident spectrum and the crop canopy reflection spectrum divided by the integration time by the radiometric calibration coefficient of the corresponding light path respectively to obtain the radiance values of the solar incident spectrum and the crop canopy reflection spectrum at different points; and respectively dividing the radiance values of the crop canopy reflection spectra at different point positions by the radiance values of the sunlight incidence spectra to obtain the reflectivity of the crops at different point positions.

And S205, inverting parameters representing plant phenotypic physiology and structure.

In order to further verify the effectiveness of the invention, in this embodiment, wheat is used as an observation object to test the operation condition of the system, fig. 4 is a graph of the reflectance of each cell calculated by spectral data acquired in a certain cycle, as can be seen from fig. 4, the curve is overall smooth, reflection peaks near 688nm and 762nm can be observed due to the contribution of fluorescence, in addition, the reflectance of each cell has obvious difference, and these reflectance data can be used for calculating the dynamic change of the structural information of the plant growth stage. Fig. 5(a) and 5(b) show the seasonal and daily dynamic changes of the phenotypic physiological parameters (for example, far-red SIF and red-band SIF) of different experimental groups and control groups, and it can be seen from fig. 5(a) and 5(b) that the system can continuously obtain high-frequency phenotypic physiological parameters for a long time, and secondly, the difference between the experimental group and the control group can be well observed. FIGS. 6(a) and 6(b) show the seasonal and daily dynamic changes of the phenotypic structural parameters (for example, NDVI and NIRv) of different experimental groups and control groups, and it can be seen from FIGS. 6(a) and 6(b) that the system can obtain the phenotypic structural differences of different growth stages of plants.

According to the method provided by the invention, the vegetation canopy ultra-high spectrum data of a time sequence can be obtained and used for calculating the radiance of the sun and the canopy so as to calculate the reflectivity and inversion phenotype parameters. Scientifically has important significance for understanding the dynamic change of structure and physiological information and the interactive regulation and control mechanism of genes and environment in the plant growth and development process, and is favorable for accelerating the breeding process and optimizing the cultivation management measures by providing a novel technical means with no damage, high flux and high precision in production.

The above-described embodiments are merely illustrative of the preferred embodiments of the present application, and do not limit the scope of the present application, and various modifications and improvements made to the technical solutions of the present application by those skilled in the art without departing from the spirit of the present application should fall within the protection scope defined by the claims of the present application.