EP4061114A1

EP4061114A1 - Method for determining and optimising the content of at least one plant constituent in at least one part of a plant

Info

Publication number: EP4061114A1
Application number: EP20811314.2A
Authority: EP
Inventors: Volkmar KEUTER; Dennis SCHLEHUBER; Annette SOMBORN-SCHULZ; Holger Wack; Stephan Deckert; Victor Takazi KATAYAMA; Felix THOMA
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 2019-11-22
Filing date: 2020-11-20
Publication date: 2022-09-28
Also published as: WO2021099588A1; DE102019131650A1; US20230044049A1

Abstract

The invention relates to a method for determining the content of at least one plant constituent (1) in at least one part of a plant (3). According to the invention, so that the content of plant constituents, in particular secondary plant constituents, in at least one part of a plant can be determined and optimised more expediently, the at least one part of the plant (3) is irradiated successively with light (7) of different wavelengths and/or wavelength ranges, and, as a response to the irradiation of the at least one part of the plant (3) with light (7) of each wavelength and/or each wavelength range, the chlorophyll fluorescence (9) of at least substantially the same wavelength and/or at least substantially the same wavelength range is measured.

Description

Method for determining and optimizing the content of at least one plant constituent of at least part of a plant

The invention relates to a method for determining the content of at least one plant ingredient in at least part of a plant. The invention also relates to a method for optimizing the content of at least one plant constituent of at least one plant at the time of harvesting the at least one plant.

In the agricultural production of plants, two basic principles are in the foreground, of which one principle dominates the other. For example, for economic reasons, in many cases the aim is to produce plants that are as large as possible, which consequently achieve a large yield. In other cases, the size of the plants is less important. In these cases, what matters is the ingredients of the plants. Such plants are, for example, herbs, aromatic plants, medicinal plants or medicinal plants. In the case of these plants, the proceeds that can be achieved depend on the content of certain phytonutrients. The corresponding content of plant ingredients is usually determined after the harvest using chemical or physical analysis methods. The corresponding contents depend on the season and should only be recorded after the harvest, so that no or only a very inadequate influence can be exerted on the content of plant constituents in the plants to be harvested.

Phytonutrients can be divided into primary phytochemicals and secondary phytochemicals. The primary plant constituents include the substances that are essential for plant growth, such as chlorophyll. There are different types of chlorophyll that are common can occur in a plant. The secondary plant constituents protect the plant against UV radiation, other weather influences and predators, for example. In addition, many phytonutrients are considered beneficial for human health. These secondary phytonutrients are especially formed by the plant under stress. The stress on the plant can be triggered, for example, by moisture, drought, heat, cold, carbon dioxide content in the air, shifting the day-to-night cycle, unfavorable lighting conditions, UV radiation, touching the plant or damaging the plant. However, the complicated mechanisms behind it are not yet sufficiently understood.

The secondary plant constituents include, for example, alkaloids, amino acids, polyphenols, anthocyanins and flavonols. While the secondary plant constituents are mainly deposited in the epidermis of the leaves, i.e. near the leaf surface, chlorophyll occurs in the palisade tissue below the epidermis. Chlorophyll absorbs light energy, most of which is used for photosynthesis. A part of the light energy that cannot be used but is nevertheless absorbed is emitted again in the form of fluorescence, the so-called chlorophyll fluorescence (ChlF), in the area of the dark red color spectrum of light.

Efforts have already been made to use this chlorophyll fluorescence to draw conclusions about the condition of the plants, such as the nitrogen content and the ability of the plants to absorb radiation. However, conclusions about the quality of living plants cannot yet be drawn to a satisfactory extent, let alone to adapt the growth conditions for the plants in such a way that a satisfactory quality of the plants can be ensured.

The invention is therefore based on the object of designing and developing the method of the type mentioned at the beginning and described in greater detail in such a way that the content of plant constituents, in particular secondary ones Plant constituents, can be determined and optimized more appropriately from at least part of a plant.

This object is achieved according to claim 1 by a method for determining the content of at least one plant ingredient of at least part of a plant,

- in which the at least one part of the plant is successively irradiated with light of different wavelengths and / or wavelength ranges and

- in which, in response to the irradiation of the at least one part of the plant with light of each wavelength and / or with each wavelength range, the chlorophyll fluorescence is measured at least essentially the same wavelength and / or at least essentially the same wavelength range.

The stated object is also achieved according to claim 13 by a method for optimizing the content of at least one plant constituent of at least one plant at the time of harvesting the at least one plant,

- in which the content of the at least one plant ingredient of at least part of the at least one plant is determined using a method according to any one of claims 1 to 12.

The invention is based on the fact that light hitting a plant is absorbed to different degrees by primary and secondary plant constituents. The unabsorbed light is partly reflected back by the plant (reflection) and partly passes through the plant (transmission), whereby the corresponding proportions can vary greatly from plant to plant and from wavelength to wavelength. Many primary and secondary phytonutrients absorb light of different wavelengths to different degrees. Some plant constituents absorb light in a very narrow wavelength range and others in a broader wavelength range, whereby the The proportion of the absorbed radiation also varies within the respective wavelength range and has an absorption maximum or several local absorption maxima in this wavelength range. The proportion of the absorbed radiation plotted over the wavelength results in a more or less characteristic curve for many plant constituents. In the case of several absorption maxima over this curve, one of the absorption maxima is usually by far the greatest in absolute terms. Due to the large number of existing plant constituents and their varying contents in the plant, conclusions cannot easily be drawn from the reflected, absorbed and / or transmitted light of a certain wavelength about the content of a secondary plant constituent.

However, the invention takes into account that the chlorophyll fluorescence (ChlF) of a plant, in particular a leaf, depends on how much light actually penetrates to the chlorophyll in the palisade tissue. The proportion of this light is lower, the more light is already absorbed in the epidermis by secondary plant constituents. Since this relationship occurs differently at different wavelengths, the at least one part of the at least one plant is irradiated with light of at least two different wavelengths and / or of at least two different wavelength ranges. In response to the irradiation with the first wavelength or the first wavelength range, the chlorophyll fluorescence is measured at a specific wavelength and / or in a specific wavelength range. The same occurs in response to the irradiation with the second wavelength or the second wavelength range. If necessary, the same thing also takes place in response to the irradiation with further wavelengths and / or wavelength ranges.

In this context, it goes without saying that very narrow wavelength ranges are preferred for irradiation. If, on the other hand, the wavelength ranges are very broad, the more different interactions overlap. Especially It is therefore preferred if the light for irradiating the at least one part of the sheet, that is to say the respective excitation radiation, is at least almost monochromatic. For practical reasons, it can be expedient to irradiate the at least part of the at least one plant with light sources which emit a certain wavelength range. LEDs are particularly suitable here, the light of which is almost, but not necessarily exactly, monochromatic, i.e. has only one wavelength. The wavelength ranges preferably include wavelength intervals of less than 100 nm, preferably less than 50 nm, in particular less than 20 nm, further in particular less than 10 nm.

The measurement results of the chlorophyll fluorescence obtained in this way can be used to infer the content of at least one plant substance. For the sake of simplicity, the chlorophyll fluorescence can be recorded over the entire wavelength range of the chlorophyll fluorescence. However, it is also conceivable to detect the chlorophyll fluorescence only in a certain wavelength range or only at a certain wavelength or at certain wavelengths, for example to enable a more precise evaluation. If necessary, the spectrum of the chlorophyll fluorescence can alternatively or additionally also be recorded when recording the chlorophyll fluorescence, it being conceivable that the wavelengths or the wavelength range are recorded at which or in which the chlorophyll fluorescence occurs. Alternatively or additionally, the chlorophyll fluorescence can also be recorded depending on the wavelength of the chlorophyll fluorescence spectrum, ie the distribution or the “shape” of the chlorophyll fluorescence over the wavelength. The determination of the spectrum of the chlorophyll fluorescence can also be limited to a wavelength range that is smaller than the entire wavelength range in which the chlorophyll fluorescence occurs.

The spectrum of the chlorophyll fluorescence can be recorded, for example, with a so-called hyperspectral camera. Such cameras take pictures of a large number of closely spaced wavelengths. Thereby If necessary, hyperspectral data cubes can be formed that have two spatial dimensions (spatial directions) and one spectral dimension (spatial direction ).In the hyperspectral data cubes, the information about the chlorophyll fluorescence is then contained, for example as a kind of response function, for the purpose of evaluation.

The spectrum of chlorophyll fluorescence depends on plant-specific factors and light effects, such as the LHC (Light Harvesting Complex) or the NPQ (Non Photochemical Quenching). Instead of generating an integral over the spectrum of the chlorophyll fluorescence and outputting the value of the integral as a gray value, the spectrum of the chlorophyll fluorescence as such can alternatively or additionally be used for the evaluation. For each excitation wavelength, a large number of chlorophyll fluorescence values for different wavelengths up to a continuous fluorescence spectrum can be used as the basis for further evaluation.

In addition, it can in particular be appropriate if a wavelength or a wavelength range for irradiating the at least one part of the plant is in the vicinity of the absolute absorption maximum of the at least one plant constituent. Then a particularly large amount of light is absorbed by the at least one plant ingredient, namely the more the greater the content or concentration of the at least one plant ingredient in the leaf or in the epidermis of the leaf. If a further wavelength or a further wavelength range is selected in such a way that at this wavelength or in this wavelength range there is no or only very little absorption of light by the at least one secondary plant constituent, these measured values of the chlorophyll fluorescence can be particularly useful for a comparison with the The aim can be used to derive a statement about the content of the at least one plant ingredient. Under certain circumstances, however, this can be impaired by the fact that at the last-mentioned wavelength or the The latter wavelength range another secondary plant constituent absorbs a large part of the light. Analogously, however, there can also be a restriction in the determination of the content of the at least one plant ingredient if at the first-mentioned wavelength or in the first-mentioned wavelength range another secondary plant ingredient of varying content shows a pronounced absorption capacity. Then it may not be clear to which plant constituent the absorption of the corresponding wavelength or the corresponding wavelength range can be attributed.

In addition, it must be taken into account, if necessary, that the chlorophyll fluorescence depends not only on the wavelength of the excitation radiation, but also on the intensity of the excitation radiation. In principle, the greater the radiation intensity at a certain wavelength, the greater the chlorophyll fluorescence. It can therefore be useful in principle to normalize the values of the chlorophyll fluorescence, for example, to the radiation intensity of the excitation radiation and / or to set the radiation intensity for all or each of the excitation radiations. Then particularly reproducible measurement results can be obtained.

The information obtained in the corresponding way about the content of the at least one plant ingredient can also be used to optimize the content of the at least one plant ingredient. If necessary, experience from the past can be used to determine which measures, in which cases, had a positive influence on the content of the at least one plant ingredient. In addition, the method described can be used to better recognize and understand these relationships. For example, the growth conditions can be observed and / or changed over the growth of the plants and, in parallel, the effects on the content of the at least one plant constituent can be determined using the appropriate method. For the sake of better understanding and to avoid unnecessary repetition, the two methods are described below together, without distinguishing between the two methods in each case. However, the person skilled in the art can see from the context which features are particularly preferred for which method.

In a first particularly preferred embodiment of the method for determining the content of at least one plant ingredient, the measured values of the chlorophyll fluorescence are compared with one another and / or with reference values in order to infer the content of the at least one plant ingredient based on empirical values, for example. This comparison can preferably be based on the values of the chlorophyll fluorescence as a function of the wavelengths and / or labor length ranges used for the irradiation. The wavelengths and / or wavelength ranges can namely have a not inconsiderable influence on the chlorophyll fluorescence. In other words, as a response to the irradiation, response signals in the form of chlorophyll fluorescence for a certain wavelength can be obtained and compared. Alternatively or additionally, the response signals for a wavelength range of chlorophyll fluorescence can also be compared. In addition, the response signals for different wavelengths and / or labor length ranges of the chlorophyll fluorescence can each be compared separately. In order to obtain a more reliable statement, the results of comparisons for different wavelengths and / or wavelength ranges can also be compared with one another.

In this way, conclusions can be drawn about the content of at least one specific secondary plant constituent. This can be done, for example, by measuring different plants or leaves in the manner described and then performing a chemical or physical analysis of the plants or leaves using conventional methods. If necessary, an Art Library can be created from reference values with which real measurement results can later be compared and evaluated in this way. Alternatively or additionally, correlations can be determined, if necessary, with the aid of the method described and accompanying conventional analyzes, which can later be used to determine the content of plant constituents without additional conventional analysis.

Since different plant constituents play a role in the light absorption of a plant, in particular a leaf, which can also vary greatly depending on the respective condition of the plant, it is particularly preferred to carry out the irradiation successively with more than two, if necessary, as many wavelengths as possible . In this way, the different interactions can be taken into account and, based on the additional information from the chlorophyll fluorescences, conclusions can be drawn more reliably about the content of the at least one plant constituent. Thus, the at least one part of the plant can be sequentially irradiated with light of at least three, preferably of at least four, in particular of at least five, different wavelengths and / or wavelength ranges, in response to the irradiation of the at least one part of the plant with light from the at least three, preferably of the at least four, in particular of the at least five, different wavelengths and / or wavelength ranges in each case the chlorophyll fluorescence is measured at least essentially the same wavelength and / or at least essentially the same labor length range. It goes without saying that the irradiation can also take place with significantly more than five different wavelengths and / or wavelength ranges. With a sufficiently high number of wavelengths and / or wavelength ranges, if necessary, an almost continuous course of the chlorophyll fluorescence over the wavelength can be generated, which can then be evaluated particularly precisely using mathematical methods known per se. In order to be able to make more precise statements about the content of the at least one plant ingredient, it is fundamentally advisable if at least one of the different wavelengths and / or wavelength ranges is at least essentially in the range of the maximum absorption of a plant ingredient. This applies in particular when the at least one absorption maximum is selected from the at least one plant ingredient of which the content is to be determined. It can also be provided, especially when using several wavelengths and / or wavelength ranges, that at least two, in particular at least three, of the different wavelengths and / or wavelength ranges at least essentially in the region of the absorption maximum of at least two, in particular of at least three, plant ingredients to get voted. Here, too, the absorption maxima can be selected at least partially from plant constituents, of which the content is to be determined. It is further understood that four, five, six or more wavelengths and / or wavelength ranges can also be selected analogously.

Alternatively or additionally, at least one of the different wavelengths and / or wavelength ranges can be selected at least essentially in the region of the absorption maximum of a chlorophyll. In this way, the value of the chlorophyll fluorescence assigned to the absorption maximum of the at least one chlorophyll can be used as a reference value for determining the content of the at least one plant ingredient. It is also conceivable that the determined values of the chlorophyll fluorescence are normalized based on the chlorophyll fluorescence for the absorption maximum of chlorophyll.

If a response function is recorded from the measured values of the chlorophyll fluorescence as a function of the wavelengths and / or wavelength ranges used for the irradiation, this can be evaluated easily, reproducibly and quickly using mathematical methods known per se. If necessary, the response function can be evaluated by a comparison with reference response functions. The reference response functions can in particular be taken from a reference library for corresponding response functions to which certain contents of the at least one plant ingredient are assigned. The content of the at least one plant ingredient corresponds, for example, approximately to the content assigned to the reference response function, which corresponds best to the recorded response function. As an alternative or in addition, a curve fitting can be carried out using the wavelength-dependent response function, which is also referred to as curve adaptation or compensation calculation. In this way, certain parameters of a certain curve function can be calculated, which correlate with the content of the at least one plant ingredient. If necessary, the curve function, for example a specific polynomial, can be specified. However, it can also be determined which curve function can be adapted most precisely to the response function. The information about the corresponding curve function and the corresponding parameters can then correlate with the content of the at least one plant ingredient. The method of minimizing the error amount deviation, minimizing the error square deviation and higher powers, minimizing the difference between the individual value amounts, which are known per se, can be used.

If response functions Bx are recorded for different concentrations (c) of all relevant plant constituents X, and, if possible, independently of one another, the concentration dependency of the response functions for the plant constituents can thus be determined. These can then be stored in a library so that they can be used as the basis of a curve function for curve fitting, since the recorded response function can potentially be viewed as a superimposition of response functions from the individual plant constituents. The curve function could then have the following form, to which the measured response function M (l) can be approximated:

BReference (l) = a (c) * Bi (l) + b (c) * Bp (l) + c (c) * Bip (l) + d (c) * Bin (l) + ... + n (c) * Bc (l) The following relationship can apply for the dependence on the concentration c of the plant constituents X of the response functions Bx of the respective plant constituents X:

Bc (l, o) = n (c) * Bc (l) with n = px (c)

The response functions of the plant ingredients for the library could in particular be determined separately on the basis of a so-called artificial leaf reproduced in the laboratory as a function of the wavelength of the irradiation. The artificial leaf could have an artificial epidermis layer and an artificial layer of palisade tissue, which are modeled on the tactile layers of a real leaf and can each have predetermined concentrations of chlorophyll in the artificial layer of the palisade tissue and the corresponding secondary plant constituents in the artificial epidermis layer . It must be taken into account that different plants and different leaves of a plant can differ in terms of their leaf structure, so that conclusions can only be drawn from one type of leaf to another type of leaf or from one plant to another plant.

Alternatively or additionally, the frequencies recorded over the time of irradiation with different wavelengths and / or wavelength ranges can be used to determine a frequency spectrum by means of a Fourier transformation, in particular Fast Fourier Transformation (FFT), on which a comparison can be based. The Fourier transformation does not take place here on a time-dependent signal, but on a wavelength-dependent signal, in particular on such a response function. Alternatively or additionally, a curve discussion can also be carried out and evaluated using the response function. Conclusions about the content of the at least one plant ingredient can then be drawn on the basis of maxima, minima, turning points, slopes and / or curvatures, in particular in certain areas of the response function become. It is also conceivable that integrals and / or partial integrals of the response functions enable conclusions to be drawn about the content of the at least one plant ingredient.

The chlorophyll fluorescence can also be recorded in a location-dependent or location-resolved manner, so that different locations on a leaf, different locations on a plant and / or different plants can be viewed and evaluated separately at the different wavelengths and / or wavelength ranges of the irradiation. Consequently, in response to the irradiation of the at least one part of the plant with light of each wavelength and / or with each wavelength range, the chlorophyll fluorescence at least essentially the same wavelength and / or at least essentially the same wavelength range at different locations of the at least one part of the plant can be measured. In this way it can be avoided that local differences superimpose one another and lead to an imprecise determination of the content or the concentration of the at least one plant ingredient. As an alternative or in addition, the content or the concentration of the at least one plant constituent can be examined in a targeted manner at certain points on a leaf, different points on a plant and / or different plants. For a spatially resolved recording of the chlorophyll fluorescence, it is advisable if the chlorophyll fluorescence is recorded by means of a corresponding sensor, preferably a camera, in particular an IR camera and / or a hyperspectral camera. In the latter cases, the chlorophyll fluorescence can be measured separately at different pixels and / or pixel areas of the images recorded by the camera.

In this context, it is advisable if the measured values of the chlorophyll fluorescence for each location, in particular for each pixel and / or each pixel area, are compared separately with one another and / or with reference values. The comparison tends to be all the more meaningful if the corresponding values of the chlorophyll fluorescence depend on the irradiation used wavelengths and / or wavelength ranges are compared with the reference values. In this way, a location-dependent detection of the content of the at least one plant ingredient can be achieved. Alternatively or additionally, response functions can be recorded separately from the measured values of the chlorophyll fluorescence for each location, in particular for each pixel and / or each pixel area, depending on the wavelengths and / or wavelength ranges used for the irradiation. These response functions can then be evaluated particularly expediently, in particular using known mathematical methods. The evaluation can be carried out, for example and in a simple manner, in that the respective response functions assigned to the individual locations, in particular pixels, are evaluated by a comparison with reference response functions, by curve fitting or by curve adaptation or compensation calculation and / or by a curve discussion. In particular, the advantages already indicated in this context are achieved here.

It is particularly expedient for the production of suitable plants if the content of the at least one plant constituent is at least part of a leaf of a plant, a leaf of a plant, several leaves of a plant, all leaves of a plant, an entire plant, at least parts of several Plants or a total of several plants is determined. In this context, the corresponding area of the at least one plant should be irradiated with the different wavelengths and / or wavelength ranges and the chlorophyll fluorescence of the corresponding areas should be measured. It can therefore be provided that at least part of a leaf of a plant, a leaf of a plant, several leaves of a plant, all leaves of a plant, an entire plant, at least parts of several plants or several plants are irradiated with light of different wavelengths and / or wavelength ranges and that the chlorophyll fluorescence of a specific wavelength and / or a specific wavelength range of the at least part of a leaf of a plant, a leaf of a plant, several leaves of a plant, all leaves of a Plant, an entire plant, at least parts of several plants or of several plants is measured.

If necessary, the chlorophyll fluorescence can be recorded by means of a camera and the images from the camera or certain pixels or pixel areas of the images from the camera can be converted or converted into gray values. The corresponding gray values can then be assigned values of the chlorophyll fluorescence. In particular, the associated gray values can be determined in advance for certain known values of the chlorophyll fluorescence in order to be able to draw conclusions later from the recorded gray values about specific chlorophyll fluorescences.

It is particularly expedient to examine living plants or parts of living plants using the appropriate method, with the corresponding parts also not being separated from the plant or otherwise permanently and irreversibly disturbed. In other words, the at least one plant constituent of at least part of a plant is determined in vivo. The biomass to be harvested in the future is therefore not reduced, or at least not significantly reduced, even by a great number of studies of the type mentioned. Furthermore, it can be expedient not to determine, or not only, the content of the at least one plant ingredient, but rather to determine a concentration of the at least one plant ingredient in the plant and / or in a specific part of the plant. Usually the concentration cannot be increased above a certain maximum, which is of particular importance for harvesting the plants.

In order to improve the determination of the content and / or the concentration of the at least one plant ingredient, the at least one part of the plant can be irradiated successively with pulsed light of different wavelengths and / or wavelength ranges. The chlorophyll fluorescence values obtained in this way are then more reproducible. Furthermore, the chlorophyll fluorescence can optionally take place in transmission and / or reflection based on the irradiation of at least one part of the plant. However, it is easier mostly the arrangement of the at least one radiation source and the at least one sensor above the at least one plant. This is also less likely to lead to undesirable shadowing effects. In many cases, therefore, the detection of the chlorophyll fluorescence in reflection will be preferred.

In a first particularly preferred embodiment of the method for optimizing the content of at least one plant ingredient of at least one plant at the time of harvest of the at least one plant, the harvest time is selected according to the determined content of the at least one plant ingredient of the at least one part of the at least one plant. If the corresponding content of the plant ingredient is not satisfactory, the harvest is awaited and, if necessary, an attempt is made in the meantime to increase the content of the at least one plant ingredient, for which purpose the growth conditions can be adjusted if necessary. The growth conditions of the plants can be the humidity, the light intensity, the light wavelength range, the temperature, the C02 content of the air, the supply of nutrients and the day-night cycle.

Alternatively or additionally, however, at least one growth condition of the at least one plant can also be controlled, in particular regulated, on the basis of the determined content of the at least one plant constituent of the plant according to predetermined criteria. In this way, the content of the at least one plant ingredient can be increased in a targeted manner. This can take place, for example, at certain suitable growth phases of the plants or only shortly before harvest. For example, on the one hand, strong growth of the plant can be achieved through suitable growth conditions and, on the other hand, the production of the secondary plant constituents can be stimulated at certain times. These objectives are mostly opposite, because a strong growth in size usually occurs with little stress on the plants, while the production of certain secondary plant constituents is stimulated by stress on the plant. The invention is explained in more detail below with the aid of a drawing that merely represents exemplary embodiments.

1 shows a method according to the invention in a schematic representation,

2A-B the absorption capacity of chlorophyll and the chlorophyll fluorescence as a function of the wavelength,

3 shows the chlorophyll fluorescence of a leaf detected with the method according to FIG. 1 as a function of the wavelength of the excitation radiation,

FIGS. 4A-B show alternative configurations of the method shown in principle in FIG. 1 and FIG

5 shows exemplary spectra of the chlorophyll fluorescence. In FIG. 1, a method for determining the content of at least one plant ingredient 1 of a leaf 2 of a plant 3 is shown schematically. The leaf 2 has a layer called epidermis 4 near the surface, in which, among other things, secondary plant constituents 1 are contained. Below this epidermis 4, the sheet 2 has a layer called palisade fabric 5, in which chlorophyll 6, here the two types chlorophyll a and chlorophyll b, is contained. The corresponding sheet 2 is successively irradiated with radiation 7, the excitation radiation, in the form of light of different wavelengths li-1A, for which purpose different radiation sources 8 in the form of LEDs are used in the method shown, which is preferred in this respect. The light or the excitation radiation 7 is partially absorbed in the epidermis 4 of the leaf 2 by secondary plant constituents 1 on its way into the palisade tissue 5 of the leaf 2. This part of the radiation 7 which is absorbed in the epidermis 4 and which is possibly reflected, consequently does not reach the palisade fabric 5 and the chlorophyll 6 there in the leaf. In the palisade fabric 5 is the the remaining part of the radiation 7 is again partially absorbed. However, the chlorophyll 6 cannot use the entire radiation energy for photosynthesis and emits part of the absorbed radiation energy in the form of the so-called chlorophyll fluorescence 9 (ChlF). The intensity of the chlorophyll fluorescence 9 is dependent on the radiation intensity, which is also referred to as radiation intensity, and on the wavelength 1 of the excitation radiation 7.

The chlorophyll fluorescence 9 is detected for each of the excitation radiations 7 with the aid of a sensor 10, in the present case in reflection, that is to say from the same side of the sheet 2 from which the sheet 2 was irradiated with the excitation radiation 7. The sensor 10 for detecting the chlorophyll fluorescence 9 in the illustrated embodiment is an IR camera (infrared camera). The sensor 10 detects radiation in the infrared wavelength range. Pairs of values of chlorophyll fluorescence 9 and excitation radiation 7 are then formed, which are used for further evaluation.

The intensity of the chlorophyll fluorescence 9 recorded by the sensor 10 is basically greater, the more radiation is absorbed by the chlorophyll 6. For this reason, the chlorophyll fluorescence 9 tends to decrease if more radiation is absorbed in the epidermis 4 and if the radiation intensity of the excitation radiation 7 is reduced. The proportion of the absorbed radiation 7 basically decreases with the content of the plant constituents 1 which at least partially absorb the radiation 7 of the respective wavelength 1. Since the content of the plant constituents 1 remains constant during the measurement on a part of a plant 3, such as on a leaf 2 of the plant 3, the plant constituents 1 absorb the radiation 7 from the different radiation sources 8 to different degrees in the different labor length ranges a characteristic response function 11 to the irradiation as the labor length dependence of the chlorophyll fluorescence 9 can be obtained. The different radiation intensity of the radiation 7 as a result of different Absorption and chlorophyll fluorescence 9 of different strengths is illustrated in FIG. 1 by the different line thicknesses of the arrows characterizing the corresponding excitation radiation 7 and chlorophyll fluorescence 9. 2A shows the wavelength-dependent absorption of chlorophyll a 6.1 and chlorophyll b 6.2 and the wavelength-dependent chlorophyll fluorescence 9. The chlorophyll fluorescence 9 comprises wavelengths greater than 650 nm, while the absolute absorption maxima are in the range between 400 nm and 500 nm.In contrast, FIG. 2B shows the wavelength-dependent absorption of exemplary secondary plant constituents 1.1-1.3, each of which has different local absorption maxima exhibit. The chlorophyll fluorescence 9 therefore depends to a large extent on the excitation wavelength 1 and the composition of the leaf being examined, in particular on the contents or concentrations of the secondary plant constituents 1. In FIG. 3, response functions 11 are exemplarily shown over the wavelength 1 of the excitation radiation 7, which was recorded with the previously described method for different concentrations c1-c3 of a certain plant ingredient 1 in the epidermis 4 of an artificially modeled leaf. The absolute values of the chlorophyll fluorescence 9 are not only lower with increasing concentration, the form of the response function 11 also varies to a certain extent with the concentration of the plant constituent 1. For this reason, the corresponding response function 11, especially after normalization to the same radiation intensity can be compared with response functions from a library for known concentrations of the phytonutrients 1. It may be useful not to compare the recorded response function 11 of the chlorophyll fluorescence 9 itself, but rather a function 12 that is approximated or fitted to the recorded response function 1, possibly standardized, in particular to the radiation intensity, with the functions of a library. A comparison of certain parameters also comes in here the corresponding functions, for example in the form of polynomials, in question. The response functions 11 stored in the library can also have been recorded on artificially modeled leaves, because different compositions, in particular of the secondary plant constituents 1, can easily be set in this way. The response functions 11 can alternatively or additionally also be determined on real leaves 2 and the composition of the examined leaves 2 can be analyzed in a conventional manner. In this way, if necessary, more realistic response functions 11 can be obtained and / or the response functions 11 determined on artificial leaves can be at least partially verified.

However, provision can also be made for at least one characteristic value of the response function 11 to be determined, likewise if necessary after a normalization of the response function 11. This can be, for example, a slope of the response function 11 in a specific wavelength range and / or the ratio of specific local maxima of the response function 11. Such a characteristic parameter could also be an integral or a partial integral in a specific wavelength range. It is also conceivable that it is useful to determine different plant constituents 1 to determine different characteristic values or to compare them with corresponding values from a library.

FIGS. 4A-B relate to alternative configurations of the method shown in principle in FIG. 1. In this case, according to the schematic representation of FIG. 4A, not only a single sheet 2 or a specific section of a sheet 2 is irradiated with different excitation length 7 to generate a characteristic chlorophyll fluorescence 9. Rather, the entire plant 3 is irradiated. The direction of the irradiation and the direction from which the chlorophyll fluorescence 9 is detected are preferably specified in order to examine the same plant 3 at different times using the corresponding method with regard to the content of at least one plant ingredient 1. Since the composition of the phytonutrients 1 in a plant 3 changes from leaf 2 to leaf 2 can clearly differ, to increase the informative value and / or to avoid many individual measurements on many individual leaves 2, it may be advisable to examine the entire plant 3 at the same time. If certain types of plants are planted in large numbers on a large area, it can also be useful if a whole group of plants 3 is examined together at the same time. This is shown schematically in FIG. 4B. This takes into account the fact that the contents of certain plant constituents 1 can differ greatly from location to location. For the sake of simplicity and reproducibility, it is advisable to examine a group, particularly a large group, of plants together

3 in particular in a greenhouse 13.

Exemplary spectra of the chlorophyll fluorescence are shown in FIG.

List of reference symbols

1 plant ingredient

2 sheets

3 plant

4 epidermis

5 palisade fabrics

6 chlorophyll

7 Stimulus labor length

8 radiation source

9 chlorophyll fluorescence

10 sensor

11 Answer function

12 function

13 greenhouse

Claims

Patent claims

1. A method for determining the content of at least one plant ingredient (1) of at least part of a plant (3),

- in which the at least one part of the plant (3) is successively irradiated with light (7) of different wavelengths and / or wavelength ranges, and

- In the response to the irradiation of at least one part of the plant (3) with light (7) of each wavelength and / or with each wavelength range in each case the chlorophyll fluorescence (9) at least substantially the same wavelength and / or at least in Essentially the same wavelength range is measured.

2. The method according to claim 1, in which the measured values of the chlorophyll fluorescence (9), preferably as a function of the wavelengths and / or wavelength ranges used for the irradiation, are compared with one another and / or with reference values.

3. The method according to claim 1 or 2,

- in which the at least one part of the plant (3) is successively irradiated with light (7) of at least three, preferably of at least four, in particular of at least five, different wavelengths and / or wavelength ranges and

- In the response to the irradiation of the at least one part of the plant (3) with light (7) from the at least three, preferably from the at least four, in particular from the at least five, different wavelengths and / or wavelength ranges in each case the chlorophyll fluorescence (9) at least substantially the same wavelength and / or at least substantially the same labor length range is measured.

4. The method according to any one of claims 1 to 3,

- at the at least one, preferably at least two, in particular at least three, of the different wavelengths and / or wavelength ranges at least essentially in the region of the absorption maxima of one plant ingredient (1), preferably of at least two plant ingredients (1), in particular of at least three plant ingredients ( 1), is chosen and

- in which, preferably, the at least one absorption maximum of the at least one plant ingredient (1) is selected, of which the content is to be determined.

5. The method according to any one of claims 1 to 4,

- in which at least one of the different wavelengths and / or wavelength ranges is selected at least essentially in the range of the absorption maxima of a chlorophyll (6) and

- in which, preferably, the value of the chlorophyll fluorescence (9) assigned to the absorption maxima of the at least one chlorophyll (6) is used as a reference value for determining the content of the at least one plant ingredient (1).

6. The method according to any one of claims 1 to 5,

- in which a response function (11) is recorded from the measured values of the chlorophyll fluorescence (9) as a function of the wavelengths and / or wavelength ranges used for the irradiation, and

- in which, preferably, the response function is evaluated by a comparison with reference response functions, curve fitting and / or a curve discussion.

7. The method according to any one of claims 1 to 6,

- In the response to the irradiation of at least one part of the plant (3) with light (7) of each wavelength and / or with each wavelength range in each case the chlorophyll fluorescence (9) at least substantially the same wavelength and / or at least in Essentially the same wavelength range is measured at different locations of the at least one part of the plant (3) and

- in which, preferably, the chlorophyll fluorescence (9) is detected by means of a sensor (10), preferably a camera, in particular an IR camera and / or a hyperspectral camera, and the chlorophyll fluorescence (9) from different pixels and / or pixel areas are measured separately.

8. The method according to claim 7,

- In which the measured values of the chlorophyll fluorescence (9) for each location, in particular for each pixel and / or each pixel area, are compared separately, preferably depending on the wavelengths and / or wavelength ranges used for irradiation, with one another and / or with reference values and or

- In the case of the measured values of the chlorophyll fluorescence (9) for each location, in particular for each pixel and / or each pixel area, separate response functions (11) depending on the wavelengths and / or wavelength ranges used for irradiation and, preferably, the response functions (11) assigned to the individual locations, in particular pixels and / or pixel areas, can be evaluated by a comparison with reference response functions, curve fitting and / or a curve discussion.

9. The method according to any one of claims 1 to 8,

- in which the determination of the at least one plant ingredient (1) in at least part of a leaf (2) of a plant (3), a leaf (2) of a plant (3), several leaves (2) of a plant (3) , all sheets (2) one Plant (3), an entire plant (3), at least parts of several plants (3) or of several plants (3) as a whole,

- in which at least a part of a leaf (2) of a plant (3), a leaf (2) of a plant (3), several leaves (2) of a plant (3), all of the leaves (2) of a plant (3), an entire plant (3), at least parts of several plants (3) or several plants (3) are irradiated with light (7) of different wavelengths and / or wavelength ranges, and

- in which the chlorophyll fluorescence (9) of a specific wavelength and / or a specific wavelength range of the at least part of a leaf (2) of a plant (3), of a leaf (2) of a plant (3), of several leaves (2) of a plant (3), all leaves (2) of a plant (3), an entire plant (3), at least parts of several plants (3) or of several plants (3).

10. The method according to any one of claims 1 to 9, in which the values of the chlorophyll fluorescence (9) are determined from gray values of images and / or pixels captured by means of a camera.

11. The method according to any one of claims 1 to 10,

- in which the at least one plant constituent (1) of at least part of a plant (3) is determined in vivo and / or

- in which a concentration of the at least one plant ingredient (1) is determined.

12. The method according to any one of claims 1 to 11,

- in which the at least one part of the plant (3) is successively irradiated with pulsed light (7) of different wavelengths and / or wavelength ranges and / or

- in which the chlorophyll fluorescence (9) takes place in transmission based on the irradiation of the at least one part of the plant in transmission and / or reflection.

13. Method for optimizing the content of at least one

Plant ingredient (1) of at least one plant (3) at the time of harvesting the at least one plant (3), - in which the content of the at least one plant ingredient (1) of at least part of the at least one plant (3) with a method according to a of claims 1 to 12 is determined.

14. The method according to claim 13, wherein the harvest time according to the determined content of the at least one

Plant ingredient (1) of the at least part of the at least one plant (3) is selected.

15. The method according to claim 13 or 14, in which at least one growth condition of the at least one plant (3) is controlled based on the determined content of the at least one plant ingredient (1) of the plant (3) according to predetermined criteria and / or in which at least one growth condition the at least one plant (3) is regulated according to predetermined criteria on the basis of the determined content of the at least one plant ingredient (1) of the plant (3).