Method for Determining and Optimizing the Content of At Least One Plant Substance of At Least One Part of a Plant

Abstract

Described and represented is a method for determining the content of at least one plant substance of at least one part of a plant. In order for the content of plant substances, in particular secondary plant substances, of at least one part of a plant to be determined and optimized more expediently, it is provided that the at least one part of the plant is irradiated successively with light of different wavelengths and/or wavelength ranges and that, in response to the irradiation of the at least one part of the plant with light of each wavelength and/or at each wavelength range, the chlorophyll fluorescence at least substantially the same wavelength and/or at least substantially the same wavelength range is measured in each case.

Claims

1. A method for determining the content of at least one plant substance of at least one 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 at each wavelength range, the chlorophyll fluorescence of at least substantially the same wavelength and/or at least substantially the same wavelength range is measured in each case.

2. The method according to claim 1, in which the measured values of the chlorophyll fluorescence, 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, in which the at least one part of the plant is successively irradiated with light of at least three, preferably of at least four, in particular of at least five, different wavelengths and/or wavelength ranges and in which, in response to the irradiation of the at least one part of the plant light of the at least three, preferably of the at least four, in particular of the at least five, different wavelengths and/or wavelength ranges, the chlorophyll fluorescence of at least substantially the same wavelength and/or at least substantially the same wavelength range is measured in each case.

4. The method according to claim 1, in which at least one, preferably at least two, in particular at least three, of the different wavelengths and/or wavelength ranges is selected at least substantially in the range of the absorption maxima of one plant substance preferably of at least two plant substances, in particular of at least three plant substances, and in which, preferably, the at least one absorption maximum is selected from the at least one plant substance from which the content is to be determined.

5. method according to claim 1, in which at least one of the different wavelengths and/or wavelength ranges is selected at least substantially in the range of the absorption maxima of a chlorophyll and in which, preferably, the value of the chlorophyll fluorescence assigned to the absorption maxima of the at least one chlorophyll used as a reference value for determining the content of the at least one plant substance.

6. The method according to anyone to claim 1, in which, from the measured values of the chlorophyll fluorescence, a response function is recorded as a function of the wavelengths and/or wavelength ranges used for the irradiation and in which, preferably, the response function is evaluated by comparing it with reference response functions, a curve fitting and/or a curve discussion.

7. The method according to claim 1, in which, in response to the irradiation of the at least one part of the plant with light of each wavelength and/or at each wavelength range, the chlorophyll fluorescence of at least substantially the same wavelength and/or at least substantially the same wavelength range is measured in each case at different locations of the at least one part of the plant-444, and in which, preferably, the chlorophyll fluorescence is recorded by means of a sensor, preferably a camera, in particular an IR camera and/or a hyperspectral camera, and the chlorophyll fluorescence of different pixels and/or pixel ranges is measured separately in each case.

8. The method according to claim 7, in which the measured values of the chlorophyll fluorescence for each location, in particular for each pixel and/or each pixel range, are compared separately, preferably as a function of the wavelengths and/or wavelength ranges used for the irradiation, with one another and/or with reference values and/or in which, from the measured values of the chlorophyll fluorescence for each location, in particular for each pixel and/or each pixel range, response functions are recorded separately as a function of the wavelengths and/or wavelength ranges used for the irradiation and, preferably, the respective response functions assigned to the individual locations, in particular pixels and/or pixel ranges, are evaluated by comparing them with reference response functions, a curve fitting and/or a curve discussion.

9. The method according to claim 1, in which the at least one plant substance of at least one part of a leaf of a plant, of a leaf of a plant, of a plurality of leaves of a plant of all leaves of a plant, of an entire plant, of at least parts of a plurality of plants or of a plurality of plants is determined in total, in which at least one part of a leaf of a plant, a leaf of a plant a plurality of leaves of a plant, all leaves of a plant an entire plant, at least parts of a plurality of plants a plurality of plants are irradiated with light of different wavelengths and/or wavelength ranges and in which the chlorophyll fluorescence of a certain wavelength and/or of a certain wavelength range of the at least one part of a leaf of a plan, of a leaf of a plant of a plurality of leaves of a plant, of all leaves of a plant, of an entire plant, of at least parts of a plurality of plants or of a plurality of plants is measured.

10. The method according to claim 1, in which the values of the chlorophyll fluorescence are determined from grey-scale values of images and/or pixels recorded by means of a camera.

11. The method according to claim 1, in which the at least one plant substance of at least one part of a plant is determined in-vivo and/or in which a concentration of the at least one plant substance is determined.

12. The method according to claim 1, in which the at least one part of the plant is successively irradiated with pulsed light of different wavelengths and/or wavelength ranges and/or in which the chlorophyll fluorescence takes place in transmission in relation to the irradiation of the at least one part of the plant in transmission and/or reflection.

13. The method for optimizing the content of at least one plant substance 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 substance of at least one part of the at least one plant is determined using a method according to claim 1.

14. The method according to claim 13, in which the time of harvest is selected according to the determined content of the at least one plant substance of the at least one part of the at least one plants.

15. The method according to claim 13, in which at least one growth condition of the at least one plant is controlled according to predefined criteria on the basis of the determined content of the at least one plant substance of the plant and/or in which at least one growth condition of the at least one plant is regulated according to predefined criteria on the basis of the determined content of the at least one plant substance of the plant.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The invention is explained in greater detail below by means of a drawing merely depicting exemplary embodiments. The drawing shows:

[0043] FIG. 1 a method according to the invention in a schematic representation,

[0044] FIG. 2A-B the absorption ability of chlorophyll and the chlorophyll fluorescence as a function of the wavelength,

[0045] FIG. 3 the chlorophyll fluorescence of a leaf recorded using the method according to FIG. 1 as a function of the wavelength of the excitation radiation,

[0046] FIG. 4A-B alternative configurations of the method represented in principle in FIG. 1 and

[0047] FIG. 5 exemplary spectra of the chlorophyll fluorescence.

DESCRIPTION OF THE INVENTION

[0048] A method for determining the content of at least one plant substance 1 of a leaf 2 of a plant 3 is schematically represented in FIG. 1. The leaf 2 has a layer designated as epidermis 4 close to the surface, which contains, among other things, secondary plant substances 1. Below this epidermis 4, the leaf 2 has a layer designated as palisade tissue 5, which contains chlorophyll 6, here the two types of chlorophyll a and chlorophyll b. The corresponding leaf 2 is irradiated successively with radiation 7, the excitation radiation, in the form of light of different wavelengths ki-X41, for which purpose different radiation sources 8 in the form of LEDs are used in the method represented and preferred in this respect. The light or excitation radiation 7 is partially absorbed by secondary plant substances 1 on its way into the palisade tissue 5 of the leaf 2 in the epidermis 4 of leaf 2. This part of the radiation 7 absorbed in the epidermis 4 and possibly reflected does not therefore reach the palisade tissue 5 and the chlorophyll 6 in the leaf. The remaining part of the radiation 7 is in turn partially absorbed in the palisade tissue 5. Chlorophyll 6 cannot, however, use all the radiation energy for photosynthesis and emits part of the absorbed radiation energy in the form of so-called chlorophyll fluorescence 9 (ChIF). The intensity of the chlorophyll fluorescence 9 thereby depends on the radiation intensity, which is also designated as the radiation strength, and on the wavelength k of the excitation radiation 7.

[0049] Chlorophyll fluorescence 9 is recorded for each of the excitation irradiations 7 by means of a sensor 10 and in the present case in reflection, i.e. from the same side of leaf 2 from which the leaf 2 was irradiated with the excitation irradiation 7. The sensor 10 for recording the chlorophyll fluorescence 9 is in the represented exemplary embodiment an IR camera (infrared camera). The sensor 10 records radiation in the infrared wavelength range. Value pairs of chlorophyll fluorescence 9 and excitation radiation 7 are then formed, which are used for further evaluation.

[0050] The intensity of the chlorophyll fluorescence 9 recorded by the sensor 10 is generally greater the more radiation is absorbed by the chlorophyll 6. For this reason, the chlorophyll fluorescence 9 tends to decrease when more radiation is absorbed in the epidermis 4 and when the radiation intensity of the excitation radiation 7 is reduced. In this case, the proportion of absorbed radiation 7 fundamentally decreases with the content of the plant substances 1 at least partially absorbing the radiation 7 of the respective wavelength k. Since the content of the plant substances 1 remains constant during the measurement on a part of a plant 3, such as on a leaf 2 of the plant 3, but the plant substances 1 absorb the radiation 7 of the different radiation sources 8 to varying degrees in the different wavelength ranges, a characteristic response function 11 to the irradiation can be obtained in the described manner as the wavelength dependency of the chlorophyll fluorescence 9. The different radiation intensity of the radiation 7 as a result of different absorption and varying degrees of chlorophyll fluorescence 9 is illustrated in FIG. 1 by the different line thicknesses of the arrows marking the corresponding excitation radiations 7 and the chlorophyll fluorescence 9.

[0051] The wavelength-dependent absorption of chlorophyll a 6.1 and chlorophyll b 6.2 as well as the wavelength-dependent chlorophyll fluorescence 9 is represented in FIG. 2A. 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. The wavelength-dependent absorption of exemplary secondary plant substances 1.1-1.3 is, on the other hand, represented in FIG. 2B, which each have different local absorption maxima. Consequently, the chlorophyll fluorescence 9 is highly dependent on the excitation wavelength 2\., and the composition of the examined leaf, in particular on the contents or concentrations of the secondary plant substances 1.

[0052] Response functions 11 over the wavelength X of the excitation radiation 7 are represented by way of example in FIG. 3, which were recorded using the previously described method for different concentrations c1-c3 of a certain plant substance 1 in the epidermis 4 of an artificially modelled leaf. The absolute values of the chlorophyll fluorescence 9 are thereby not only lower with increasing concentration, the shape of the response function 11 also varies to a certain extent with the concentration of the plant substance 1. For this reason, the corresponding response function 11, in particular after standardizing to the same radiation intensity, can be compared with response functions from a library for known concentrations of the plant substances 1. In this case, it may be advisable not to compare the recorded response function 11 of the chlorophyll fluorescence 9 itself, but rather to compare a function 12 approximated or adapted to the recorded response function 1, if necessary, standardized in particular to the radiation intensity, with the functions of a library. In particular, a comparison of certain parameters of the corresponding functions, for example in the form of polynomials, is also considered here. The response functions 11 stored in the library may also have been recorded on artificially modelled leaves, because this makes it easy to adjust different compositions, in particular of the secondary plant substances 1. 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. Thus, 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.

[0053] However, it can also be provided that at least one characteristic value of the response function 11 is determined, also as required after a standardization of the response function 11. This can for example be a slope of the response function 11 in a certain wavelength range and/or the ratio of certain local maxima of the response function 11. Such a characteristic parameter could also be an integral or partial integral in a certain wavelength range. Furthermore, it is conceivable that it is expedient to determine different characteristic values for the determination of different plant substances 1 or to compare them with corresponding values of a library.

[0054] FIG. 4A-B relate to alternative configurations of the method represented in principle in FIG. 1. In this case, according to the schematic representation of FIG. 4A, not only is a single leaf 2 or a certain section of a leaf 2 irradiated to generate a characteristic chlorophyll fluorescence 9 with different excitation wavelengths 7, but rather the entire plant 3 is irradiated. In this case, the direction of the irradiation and the direction from which the chlorophyll fluorescence 9 is recorded are preferably predefined in order to examine the same plant 3 at different points in time using the corresponding method with regard to the content of at least one plant substance 1. Since the composition of the plant substances 1 can differ significantly from leaf 2 to leaf 2 on a plant 3, in order to increase the significance 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 plant types are planted in large numbers over a large area, it may also be advisable to examine a whole group of plants 3 together. This is schematically represented in FIG. 4B. This takes into account the fact that the contents of certain plant substances 1 can vary greatly from location to location. For the sake of simplicity and reproducibility, it is advisable to examine together an, in particular large, group of plants 3, in particular in a greenhouse 13.

[0055] Exemplary spectra of the chlorophyll fluorescence are represented by way of example in FIG. 5.

LIST OF REFERENCE NUMERALS

[0056] 1 Plant substance [0057] 2 Leaf [0058] 3 Plant [0059] 4 Epidermis [0060] 5 Palisade tissue [0061] 6 Chlorophyll [0062] 7 Excitation wavelength [0063] 8 Radiation source [0064] 9 Chlorophyll fluorescence [0065] 10 Sensor [0066] 11 Response function [0067] 12 Function [0068] 13 Greenhouse