Gas sample collector

Abstract

A gas sampler for recording gas exchange processes on a plant leaf, comprising a sample chamber, and a corresponding method for collecting such gas samples are described. The sample chamber (1) has a sample chamber wall (2) in which an inlet (6) and an outlet (7) are arranged, and which defines a space (3) that is freely accessible via a sample chamber opening surrounded by a continuous sample chamber rim (4). A joining unit (16, 17, 18, 19) is attached along the sample chamber rim (4), which is designed to detachably join the sample chamber rim (4) to a surface of a plant leaf (5) in a fluid-tight manner such that, in the joined state, the plant leaf (5) together defines the space (3) together with the sample chamber wall (2).

Description

Technical area

[0001] The invention relates to a gas sample collector for detecting gas exchange processes on a plant leaf with a sample chamber and a related method for collecting such gas samples.

[0002] Plants, and especially trees, can communicate with each other and even warn each other of dangers, such as pest infestation, by releasing a variety of gases through the stomata, which in most woody plants are located on the underside of their leaves. The composition and quantity of the released gases depend heavily on environmental conditions and vary depending on the stress the plant is under. The gases emitted include oxygen, water vapor, carbon dioxide, and a wide variety of volatile organic compounds (VOCs). VOCs have low molar flow rates (nmol / s) and are therefore difficult to detect and measure. State of the art

[0003] The publication DE 195 22 444 C2 discloses a gas exchange chamber for recording gas exchange processes, such as those occurring during photosynthesis, i.e., during plant respiration. The known gas exchange chamber comprises a support in which a plant leaf to be examined can be clamped. On one side, the plant leaf encloses a gas-permeated measuring chamber in which at least one sensor is mounted. A lighting unit is arranged directly above the leaf surface to illuminate the leaf with a defined light wavelength and intensity.

[0004] Another approach for recording gas exchange processes on a plant leaf is described in the article by Haberstroh, S. et al. "Natural Carbon Isotope Composition Distinguishes Compound Groups of Biogenic Volatile Organic Compounds (BVOC) in Two Mediterranean Woody Species" in Frontiers in Plant Science vol. 9, p. 1071, 2018. This involves a tubular bag that is pulled over a branch bearing a large number of leaves and secured as tightly as possible. The tubular bag is connected to a hose inlet and outlet, through which the corresponding measuring gases can be extracted from the tubular bag volume. A device comparable to this known arrangement is disclosed in the publication KR 10 2022 0 057 810 A, which provides a collection bag for collecting terpenes via evaporation from a cypress tree. The bag is attached as tightly as possible over a branch area of ​​a cypress tree.A gas supply and gas discharge line are connected to the bag volume enclosed by the collection bag, which can range in size from 20 l to 100 l. These lines, in conjunction with a flow unit, ensure gas flow through the bag volume. A measuring unit located downstream of the gas discharge line measures the terpenes contained in the discharged gas stream.

[0005] Document CN 2 10 269 312 U describes a test setup in which a single leaf is completely enclosed in a so-called leaf chamber, to which a gas supply and gas discharge line is connected, which is connected to an analysis unit. During the gas test, the leaf is enclosed by the leaf chamber and thus experiences maximum stress.

[0006] WO 2021 / 011447 A1 discloses a gas sampling system from a leaf using a smartphone capable of measuring various volatile organic components via a sensor interface. For this purpose, an arrangement draws in the gases evaporated from a leaf, where the gases are subjected to a type of chromatographic analysis, which is captured and documented using the smartphone's camera unit. Description of the invention

[0007] The object of the invention is to further develop a gas sample collector for recording gas exchange processes on a plant leaf, comprising a sample chamber, in such a way that the natural gas exchange taking place in a plant leaf is disrupted as little as possible. In addition, the gas sample collection should be capable of being carried out leaf-selectively without damaging the plant leaf to be examined. Furthermore, it should be possible to design the gas sample collector to be as small, lightweight and cost-effective as possible, so that once the gas sample collector is attached to a plant leaf, it is supported by the plant leaf connected to the plant, i.e. the load acting on the plant leaf by the gas sample collector should be significantly smaller than the maximum holding force with which a plant leaf is connected to the plant.In addition, the possibility of equipping a plant with a large number of gas sample collectors on its leaves should be opened up in order to obtain information about the gas sample exchange of an entire plant via its leaves.

[0008] The solution to the problem underlying the invention is defined in claim 1. The subject matter of claim 18 is a method for collecting gas samples for recording gas exchange processes on a plant leaf. Features that advantageously further develop the inventive concept are the subject matter of the dependent claims and the further description, in particular with reference to the illustrated embodiments.

[0009] A gas sample collector according to the invention for recording gas exchange processes on a plant leaf with a sample chamber is characterized in that the sample chamber has a sample chamber wall in which an inlet and an outlet opening are arranged and which delimits a spatial area that is freely accessible via a sample chamber opening surrounded by a continuously circumferential sample chamber edge. A joining unit is attached along the sample chamber edge, which is designed to releasably and firmly join the sample chamber edge to the surface of a plant leaf in a fluid-tight manner, so that in the joined state, the plant leaf defines the spatial area together with the sample chamber wall.

[0010] The idea underlying the invention envisages minimally invasive contact and impairment of a "living" plant leaf through contact with the sample chamber. This means that even after the gas sampler is removed, the plant ball remains intact and unharmed. The gas sampler according to the solution is selected in terms of size and weight so that it adheres self-supportingly to the leaf during gas collection and influences or impairs it as little as possible, thus minimizing the stress on the leaf.

[0011] Gas exchange processes on a plant leaf predominantly occur on the underside of the leaf. Since the stomata responsible for gas exchange are located there, the sample chamber according to the solution is designed so that it can be attached gently and fluid-tight to the underside of a plant leaf, leaving the remaining surface, particularly the upper side of the leaf, exposed and largely unaffected by the gas sampler. The majority of the leaf surface is thus exposed to natural environmental conditions, such as wind, sunlight, rain, soil gases, etc., so that the plant leaf remains unaffected during gas sample collection, particularly with regard to its photosynthetic activity.

[0012] In a preferred embodiment, the sample chamber itself is half-shell-shaped or dome-shaped and has a sample chamber rim that completely surrounds the shell or dome shape and preferably defines a virtual plane. To secure the sample chamber to the underside of a plant leaf without mechanically damaging the leaf, a joining means is provided, which is preferably designed as an annular, elastic surface seal and, at least in the joined state, extends uninterruptedly along the sample chamber rim and has an opening that overlaps the sample chamber opening as extensively as possible.The elastic surface seal, which is preferably made of a transparent silicone material, ensures, on the one hand, that the sample chamber is connected to the elastic surface seal in a fluid-tight manner along its entire sample chamber edge. On the other hand, it lies fluid-tight on the underside of the plant leaf via its circular contact surface and is able to distribute the holding or contact forces required for attaching the sample chamber to the plant leaf as widely and evenly as possible on the underside of the leaf.

[0013] To generate the holding or contact forces, a preferred embodiment of the gas sample collector provides a joining means with at least two magnet units, of which a first magnet unit is or can be connected firmly or detachably to the sample chamber, and a second magnet unit is designed as a separately manageable unit. The first magnet unit can, as mentioned, either be part of the sample chamber, i.e., arranged inseparably therefrom, for example, running along the sample chamber edge, or be joined or removably joinable within the elastic surface seal. Furthermore, the sample chamber edge is joined or can be joined to the elastic surface seal in a fluid-tight manner.It is preferably advisable to provide a groove-shaped recess on a surface of the elastic surface seal opposite the plant leaf, which recess is adapted to the geometry and dimension of the sample chamber edge and is contoured accordingly, into which the sample chamber edge can be inserted in a fluid-tight manner, forming a positive-friction connection.

[0014] The second magnet unit preferably corresponds in shape and size to the first magnet unit and, when joined, can be attached congruently to the first magnet unit on the surface of the plant leaf opposite the sample chamber. Preferably, an elastic, light-transparent surface element is arranged between the second magnet unit and the plant leaf to be protected in order to, on the one hand, distribute the contact forces as evenly as possible and, on the other hand, to keep the shading effect on the upper side of the plant leaf as low as possible, so that the plant leaf can continue its photosynthetic activity as unrestrictedly as possible despite the attachment of the gas sampler. A light-transparent design of the first and, in particular, the second magnet unit is particularly advantageous, e.g., through the use of light-transparent magnetic materials.

[0015] As an alternative to the joining element in the form of two magnetic units, clamping devices subjected to tensioning force are conceivable, for example in the form of clips, which can also ensure a fluid-tight attachment of the sample chamber to the underside of the sheet in a way that is gentle on the sheet.

[0016] In addition to the sample chamber opening facing the plant leaf, the sample chamber wall also features an inlet and outlet opening for the fluid-tight connection of a gas supply line and a gas outlet line. The gas sample collector, including the gas supply and gas outlet lines required for its function, are designed to be lightweight and suitable for direct attachment to the plant leaf and along the branch supporting the plant leaf to be examined. The weight of the gas sample collector, i.e. without the gas supply and gas outlet lines, ranges from a few grams to a maximum of approximately 20 grams, depending on the leaf size and stability, as well as the associated mechanical load-bearing capacity of the plant leaf. The dimensions and shape of the sample chamber can also be adapted to the geometry and stability of the plant leaf to be examined.For example, sample chambers for examining maple leaves are larger, more stable and more difficult to construct than those for acacia leaves, for example.

[0017] All gas sample collectors according to the solution are based on the maxim that they are to be attached to the leaf in a self-supporting manner, i.e. preferably to the underside of the leaf, without impairing the leaf's biological function during and after the gas sample collection.

[0018] Not necessarily, but advantageously, the sample chamber is rotationally symmetrical to a virtual plane orthogonal to the virtual plane spanned by the sample chamber edge and rises above this in a dome-like or cupola-shaped manner. The inflow opening is preferably arranged at a greater distance from the virtual plane than the outflow opening. In this exemplary embodiment, the inflow and outflow openings are penetrated by a sectional plane containing the axis of rotation, i.e., the inflow and outflow openings are located one above the other when viewed from the side of the sample chamber. In addition, the inflow and outflow openings are arranged in the same half-plane relative to a dividing plane containing the axis of rotation and oriented orthogonal to the sectional plane, i.e., the inflow and outflow openings are each located on the same side of the sample chamber wall.A flow guide is arranged within the sample chamber, ensuring that the supply air or gas supply entering the space enclosed by the sample chamber reaches a lower region of the sample chamber near the top. The concave curvature of the sample chamber's inner wall deflects it toward the plant leaf surface, allowing it to flow over it as close to the space as possible before the gas flow exits the sample chamber via the outlet opening. Details of this embodiment are described below with reference to the figures.

[0019] Due to its low weight, low manufacturing costs and very good material availability, the gas sample collector according to the solution allows gas sample collectors to be attached to a large number of plant leaves, so that a large number of leaves, e.g. of a tree or shrub, in different areas, e.g. of a tree crown, can be examined simultaneously in order to obtain reliable statements about the photosynthesis activities in different areas of the tree crown.

[0020] A gas sampler is used as follows: First, the sample chamber is attached to the surface, preferably on the underside of a plant leaf, creating a space defined by the plant leaf and otherwise by the sample chamber. A carrier gas of a specific quality is introduced into this space. Within the sample chamber, and particularly through contact with the upper surface of the plant leaf, this carrier gas is enriched with additives formed by gas exchange processes in the plant leaf. The carrier gas enriched with these additives is then extracted from the sample chamber, collected, and subsequently analyzed. Brief description of the invention

[0021] The invention is described below, without limiting the general inventive concept, using exemplary embodiments with reference to the drawings. They show: Fig. 1aExploded view of a sample chamber designed according to the solution, Fig. 1bCross section through the sample chamber according to Figure 1a , Fig. 2 Top view of a flow guide, Fig. 3 Alternative embodiment of a sample chamber and Fig. 4 Diagram for investigating the assimilation rate in leaves with a solution-based gas sampler Ways of implementing the invention, industrial applicability

[0022] Fig. 1a shows an exploded view of a gas sample collector designed according to the solution. Fig. 1bshows a cross-section through the gas sample collector. The gas sample collector has a sample chamber 1, which has a preferably light-transparent, bowl- or dome-shaped sample chamber wall 2, which defines an inner space 3 that is freely accessible via the sample chamber rim 4, which in the illustrated case is circular. The sample chamber wall 2 is made of light-transparent material, preferably lightweight PET, and has a weight of only a few grams. The shape and size of the sample chamber 1 depend on the shape and size of the respective plant leaf 5. The sample chamber rim 4 is not necessarily circular. For example, it is conceivable to adapt the shape of the sample chamber rim 4 to the leaf shape, such as the underside of a maple leaf, where a "finger-shaped" outline would be suitable for the sample chamber rim.

[0023] Two further openings are provided in the sample chamber wall 2: an inlet opening 6 and an outlet opening 7, each of which is designed for a fluid-tight connection, namely the connection of a gas supply line 8 and a gas discharge line 9. Preferably, a fluid-dynamic adapter 10 is located at each of the inlet and outlet openings 6, 7, via which a detachable, fluid-tight attachment of the gas supply and gas discharge lines 8, 9 is possible.

[0024] In the illustrated embodiment, the inflow opening 6 and the outflow opening 7 are located along a common sectional plane that orthogonally intersects a virtual plane formed by the circular ring-shaped sample chamber edge 4. Furthermore, both openings 6, 7 are located on the same half-plane relative to a plane that orthogonally intersects the sectional plane and the virtual plane.

[0025] Between both openings 6, 7 a plate-shaped flow guide 11 is mounted, see Figure 2 , which is fluid-tightly connected to the inner wall of the sample chamber wall 2 by its circular partial circumferential edge 12. The straight side edge 13 of the flow guide 11 is spaced from the sample chamber wall 2 and thus creates a connecting region between a first sub-region 14 of the spatial region 3, into which the inflow opening 6 opens, and a second sub-region 15, into which the outflow opening 7 opens.

[0026] The gas sampler further comprises a sealing means 16 in the form of an elastic, annular surface seal, which is arranged between the sample chamber 1 and the plant leaf 5. The plant leaf 5 is a "living" plant leaf, i.e., the plant leaf 5 is connected to the plant, for example, a tree. This ensures that the plant leaf is exposed to external environmental influences and is therefore photosynthetically active.

[0027] The elastic surface seal 16 has a surface facing the sample chamber 1, in which preferably (not shown) a groove-shaped recess is introduced which is contoured to match the shape and size of the sample chamber edge 4 and into which the sample chamber 1 can be joined in a fluid-tight and permanent manner via its sample chamber edge 4.

[0028] Silicone is the preferred material for forming the elastic, ring-shaped surface seal. It has also been shown that the transmission of the silicone seal increases from at least 70% to 80% when, for example, a 10 nm thick aluminum oxide coating is applied. The coating can be adapted to the ambient conditions and can vary in thickness and material.

[0029] In order to ensure the most gentle, releasable attachment of the sample chamber 1 via the elastic surface seal 16 to the underside of the plant leaf 5, a joining means is additionally provided, which comprises a first magnet unit 17 and a second magnet unit 18. Both magnet units 17, 18 are ring-shaped and of equal dimensions. The first magnet unit 17 is integrated within the elastic surface seal 16 or releasably joined thereto and, together with the seal, comes into contact with the underside of the plant leaf 5. The second magnet unit 18 represents a separately handleable unit and comes into contact with the upper side of the plant leaf 5. Both magnet units 17 and 18 are preferably made of a light-transparent material. A light-transparent, elastic layer element 19 is also arranged between the second magnet unit 18 and the upper side of the plant leaf 5, preferably to protect the leaf.Measurements have also shown that by providing a light-transparent, elastic layer element 19 between the second magnet unit 18 and the upper side of the plant leaf 5, at least 8% of the light incident perpendicularly on the plant leaf 5 is transmitted for the wavelength range of 400-700 nm relevant for photosynthesis. Due to the magnetic attraction forces between the two magnet units 17, 18, the gas sampler adheres to the underside of the plant leaf 5.

[0030] The plate-shaped flow guide 11, together with the concavely shaped sample chamber inner wall 2 in the region of its side edge 13, redirects the carrier gas flow S entering the lower region 14 of the sample chamber 1 through the inlet opening 7 into the lower region 15, in which the carrier gas flow S flows over the underside of the plant leaf 5 and is enriched there with gas components emitted from the plant leaf 5. The carrier gas S enriched with the gas components emitted from the plant leaf 5 passes downstream through the outlet opening 7 and the gas discharge line 9 connected thereto for the purpose of gas collection and subsequent gas analysis.

[0031] Figure 3 shows an alternative design variant for the sample chamber 1, which, as in the case study according to Figure 1a, bhas a hemispherical sample chamber wall 2, but has a different arrangement of the inflow opening 6 and outflow opening 7. In the case shown, the plate-shaped flow guide 11 is oriented orthogonally to the underside of the plant leaf 5 and not as in the case according to. Fig. 1a,b parallel thereto. In this way, the flow guide 11 divides the hemispherical sample chamber 1 into two spherical quarter-segment-like sub-regions 14*, 15*, whereby in this case too, the plate-shaped flow guide 11 enables a flow transition between the two sub-regions 14*, 15* in the region of their side edge 13, which is oriented orthogonally to the virtual plane spanned by the sample chamber edge 4 and arranged at a distance from the sample chamber inner wall.

[0032] Fig. 4shows the results of the investigation of the assimilation rate [µmol m-2 s-1] after applying the gas collector according to the solution to four leaves of a beech tree. It was found that immediately after the gas collector was applied to the leaves, the assimilation rate decreased due to stress. In the days following the application, the leaves recovered, as evidenced by an increase in the assimilation rate. If, however, the leaf were disturbed, e.g., by being separated from the branch, the assimilation rate would decrease further.

[0033] Further comparative measurements using a known measurement method similar to the Haberstroh bag-type method described above, which included the detection of CO2, water, and common VOCs such as acetone, hexenal, isoprene, and acetal hyde, showed that the solution-based gas samplers provide comparable measurement results. In terms of the speed of measurement data acquisition, the solution-based gas samplers, which are mounted decentrally on the individual blades, are significantly superior to the known measurement method, especially since the gas samplers have a smaller measurement volume, thus achieving higher flow rates and thus a higher temporal resolution. List of reference symbols

[0034] 1 Sample chamber 2 Sample chamber wall 3 Room area 4 Sample chamber edge 5 Plant leaf 6 Inlet opening 7 Outlet opening 7 Gas supply line 9 Gas discharge line 10 Adapter 11 Flow guide 12 Circular partial peripheral edge 13 Side edge 14 First sub-area 15 Second sub-area 16 Sealant, elastic surface seal 17 First magnet unit 18 Second magnet unit 19 Light-transparent layer element

Claims

1. Gas sample collector for recording gas exchange processes on a plant leaf (5) with a sample chamber (1), characterized in that the sample chamber (1) has a sample chamber wall (2) in which an inlet (6) and an outlet (7) are arranged and which delimits a spatial area (3) which is freely accessible via a sample chamber opening surrounded by an uninterrupted circumferential sample chamber edge (4), and in that a joining unit is attached along the sample chamber edge (4), which is designed to releasably and firmly join the sample chamber edge (4) to a surface of a plant leaf (5) in a fluid-tight manner, so that in the joined state the plant leaf (5) delimits the spatial area (3) together with the sample chamber wall (2).

2. Gas sample collector according to claim 1, characterized in that the inflow opening (6) is or can be connected in a fluid-tight manner to a gas supply line (8) and the outflow opening (7) is or can be connected in a fluid-tight manner to a gas discharge line (9).

3. Gas sampler according to claim 1 or 2, characterized in that the sample chamber (1) has, at least in some areas, a concave sample chamber wall surface facing the spatial area (3).

4. Gas sampler according to one of claims 1 to 3, characterized in that the sample chamber wall (2) projects dome-shaped over the sample chamber edge (4).

5. Gas sampler according to one of claims 1 to 4, characterized in that the joining unit comprises a joining means for generating a holding force with which the sample chamber (1) can be joined to the plant leaf (5) under force, and a sealing means (16) for fluid-tight joining of the sample chamber (1) to the upper side of the plant leaf (5) 6. Gas sample collector according to claim 5, characterized in thatthe joining means comprises at least two magnet units (17, 18), of which a first magnet unit (17) is or can be connected fixedly or detachably to the sample chamber (1) and a second magnet unit (18) is designed as a separately handleable unit.

7. Gas sampler according to claim 5 or 6, characterized in that the sealing means (16) has an elastic surface seal which, at least in the joined state, extends uninterrupted along the sample chamber edge (4) and has an opening overlapping with the sample chamber opening.

8. Gas sample collector according to claim 6, characterized in that the first magnet unit (17) is joined or can be joined into the elastic surface seal (16), and that the sample chamber edge (4) is joined or can be joined in a fluid-tight manner into the elastic surface seal (16).

9. Gas sampler according to one of claims 6 to 8, characterized in thatthe second magnet unit (18) corresponds in shape and size to the first magnet unit (17) and, in the joined state, can be brought into contact with a surface opposite the surface of the plant leaf (5) in a manner that is not congruent with the first magnet unit (17).

10. Gas sampler according to one of claims 1 to 5, characterized in that the joining element has a clamping device with a clamping force 11. Gas sampler according to one of claims 1 to 10, characterized in that the sample chamber edge (4) spans a virtual plane over which the sample chamber (1) is raised rotationally symmetrically to a rotation axis oriented orthogonally to the virtual plane.

12. Gas sample collector according to claim 11, characterized in thatthe inflow opening (6) is arranged at a greater distance from the virtual plane than the outflow opening (7), that the inflow and outflow openings (6, 7) are penetrated by a cutting plane containing the axis of rotation, and that the inflow and outflow openings (6, 7) are arranged in a same half-plane relative to a parting plane containing the axis of rotation and oriented orthogonally to the cutting plane.

13. Gas sample collector according to claim 12, characterized in that a flow guide means (11) is arranged between the inlet and outlet openings (6, 7), which spatially separates the spatial region (3) into two sub-regions (14, 15) which are fluidically connected to one another via a local connecting region which is arranged in a half-plane opposite the half-plane in which the inlet and outlet openings (6, 7) are arranged.

14. Gas sampler according to one of claims 1 to 13, characterized in thatthe sample chamber wall (2) is made of a light-transparent material.

15. Gas sampler according to one of claims 1 to 14, characterized in that the sample chamber edge corresponds to a circular ring with an inner ring diameter D with 10 mm ≤ D ≤ 250 mm, preferably D = 30 mm ± 10 mm.

16. Gas sampler according to one of claims 1 to 15, characterized in that the sample chamber (1) and the joining unit have a shape, size and weight such that the sample chamber (1) can be joined in a self-supporting, permanently detachable and fluid-tight manner to a living plant leaf (5) connected to a plant.

17. Gas sampler according to claim 2 and 16, characterized in that the gas supply and gas discharge line (8, 9) connected to the sample chamber (1) is designed for self-supporting, permanent attachment to a branch of the plant to which the plant leaf (5) provided with the sample chamber (1) is connected.

18. Gas sampler according to one of claims 1 to 17, characterized in that the sample chamber (1) and the joining unit have a total weight between 3 grams and 50 grams.

19. Method for collecting gas samples for recording gas exchange processes on a plant leaf, characterized by The following process steps: - Forming a spatial area (3) bounded on one side by the surface of a plant leaf (5) connected to a plant, which is otherwise bounded by a sample chamber (1), - Introducing a carrier gas into the spatial area (3), - Discharging the carrier gas enriched with additives by gas exchange processes in the plant leaf. - Collecting and / or analyzing the enriched carrier gas.

20. Method according to claim 19, characterized in thatthe introduction of the carrier gas into a first sub-region (14) of the spatial region (3) which is separated from the surface of the plant leaf (5), that the discharge of the enriched carrier gas takes place from a second sub-region (15) of the spatial region (3) which is delimited on one side by the surface of the plant leaf (5), and that the sub-regions (14, 15) are connected to one another and flowed through in such a way that the carrier gas and the enriched carrier gas are oriented in counterflow to one another.