SE539510C2 - Controlling plant cell degradation - Google Patents

Description

TITLE: CONTROLLING PLANT CELL DEGRADATION TECHNICAL FIELD This technology generally concerns large-scale plant propagation in nurseries etc. and specifically concerns biodegradable fiber material pots or cells used for propagating seedlings/plants.

BACKGROUND Within the field of horticulture plants/seedlings in nurseries etc. have traditionally been propagated in plastic plant trays with loose or integrated cells until the plant plugs are ready for planting. In line with the recent increased environmental consciousness in most areas there has also been a development towards the use of environmentally friendly plant propagation products in general and towards the use of biodegradable plant pots in particular. Such biodegradable plant pots or biocontainers have been used for some decades and have come in varying forms such as pots made of decomposed cow manure, paper pulp and coconut coir and biodegradable plastic fiber pots. These types of biocontainers have the advantage that they break down naturally over time. However, if placed in a compost or at the bottom of a planting hole it may take up to three years for such biocontainers to break down.

During recent years there has also been marketed several types of small size containers that are basically a sleeve of paper, fiber, or bioplastic in which substrate is wrapped. Thus, for some time it has been known to use plant propagation pots or cells made of biodegradable fiber materials. One example of such fiber materials are thin woven or non-woven fiber sheets that mainly consist of natural fiber and biodegradable polymer fiber. The sheets are formed into a generally tubular sleeve and the opposite edges of the sleeve are interconnected in a suitable manner, such as by welding or through adhesive. Such sleeves are normally not considered to be true containers and must for most applications be supported in a tray until the substrate is held together by the developing roots. A great advantage of this type of pot is that the plant, along with the fiber cell or pot, can be put straight into the ground. This means that roots will not be disturbed and no transplant shock will be experienced.

However, presently used biodegradable fiber pots are not optimal when it comes to a proper balance between cell integrity and rapid degradation after planting and there is thus a clear demand for improvements within this field.

SUMMARY It is a general object to provide an improved solution to the above discussed problems.

In particular it is an object to suggest a method for improving the plant/seedling conditions in association with planting.

This and other objects are met by the technology as defined by the accompanying claims.

The technology generally relates to a method of forming and managing a fiber material plant propagation cell consisting of natural fiber and biodegradable polymer fiber.

In a basic aspect of the technology there is provided an improved method of controlling the future integrity of a fiber material plant propagation cell. A plant propagation cell material is formed of natural fiber and biodegradable polymer fiber, a plant propagation cell is formed from said cell material, plant substrate is filled into the plant propagation cell that is then positioned and supported in a cell carrier and a plant is introduced into the substrate of the cell. In a basic configuration the method includes applying a degradation triggering fluid to the plant propagation cell material prior to planting the plant propagation cell.

Preferred further developments of the basic idea as well as embodiments thereof are specified in the dependent subclaims and advantages offered by this technology, in addition to those described above, will be readily appreciated upon reading the below detailed description of embodiments of the technology.

BRIEF DESCRIPTION OF THE DRAWINGS The technology and its further objects and advantages will be best understood by reference to the following description taken together with the accompanying drawings, in which: Fig. 1 is a schematical illustration of a basic embodiment of a fiber material type plant propagation cell where the present technology may be applied; Fig. 2 is a schematical illustration of the basic embodiment of the fiber material type plant propagation cell of Fig. 1, filled with a plant substrate; Fig. 3 is a partial illustration of a plant carrier with fiber material type plant propagation cells of Fig. 2 received therein; Fig. 4 is a schematical illustration of one exemplifying method of applying the degradation controlling fluid to cells of Fig. 2; Fig. 5 is a schematical illustration of another exemplifying method of applying the degradation controlling fluid to cells of Fig. 2; and Fig. 6 is a very schematical illustration of test results of fiber material degradation over time using an embodiment of the present technology.

DETAILED DESCRIPTION The technology will now be described in connection with exemplifying embodiments of a method that are explained with reference to very schematical illustrations in the accompanying drawing figures. The embodiments serve to exemplify the use of the principles of the new technology in an application for the propagation of forestry plants in nurseries etc. It shall be emphasized though that the illustrations serve the purpose of explaining preferred embodiments of the technology and are not intended to limit the technology to details or to any specific field of application thereof. The presently proposed solutions may therefore with only minor adaption be applied to most types of plant propagation facilities.

It shall also be emphasized from the start that the use throughout the specification and claims the term "planting" shall not limit the technology to any specific type of plant handling. Thus, the term "planting" as used herein shall include any type of relocation of plants within as well as outside of nurseries, e.g. transplanting and replanting.

To overcome disadvantages and problems that are normally encountered within this technical field and that were briefly mentioned in the introduction the present technology now suggests a novel approach for optimizing fiber cell integrity and biodegradability. The unique features of the suggested method provide essential advantages over existing techniques. The method enables controlling the future integrity of a fiber material plant propagation cell. This cell material control in turn provides advantages such as improved and secure handling of propagation cells and simultaneous rapid degradation of the fiber cell material after planting.

The present technology will now be explained with reference to exemplifying embodiments of the technology that are illustrated in the accompanying drawing figures 1-6. Fig. 1 very schematically illustrates an exemplary embodiment of a basic fiber cell 1 as used for the present technology. Basically, a plant propagation cell material 2 is formed of natural fiber, e.g. cellulose fiber, and biodegradable polymer fiber. Expressed otherwise the cell material 2 is a natural fiber reinforced biodegradable polymer and the biodegradable polymer fiber is preferably polylactic (PLA) fiber or polyethylene terephthalate (PET) fiber or a mixture thereof. A plant propagation cell 1 is in the illustrated embodiment of Figs. 1 and 2 formed from said plant propagation cell material 2 by forming the material into a sleeve having the form of a straight cylinder. The opposite longitudinal edges of the material are then interconnected in a conventional manner, preferably by means of an adhesive, to form a longitudinal joint 3. As is briefly indicated in Fig. 1 the plant propagation cell material 2 is normally formed into a continuous sleeve that is then divided into individual cells 1 when the inner space of the sleeve has been filled with a plant propagation substrate S.

With reference to Fig. 3 several plant propagation cells, as exemplified by the cells 1.1, 1.2, are then positioned and supported in a cell carrier 20 and normally remain there during propagation in a nursery or a greenhouse etc. Finally a plant P is introduced into the plant substrate S of each plant propagation cell 1.1, 1.2.

Then, prior to planting of the plant propagation cells 1.1, 1.2 in soil, substrate or in the ground a degradation triggering or initiating fluid FL is applied to the plant propagation cell material 2. This application of the degradation triggering fluid FL is performed at some appropriate time prior to the planting of the plant propagation cells 1.1, 1.2 and the time is not specified since it may vary depending upon several circumstances that are related to a specific application. The application of the degradation triggering fluid is performed by soaking the plant propagation cell material 2 surrounding the plant substrate S with the fluid FL. Preferably the complete plant propagation cell material 2 of each plant propagation cell 1.1, 1.2 is soaked by the applied degradation triggering fluid FL, but it will likewise be possible to soak only parts of the plant propagation cell material 2 with degradation triggering fluid FL.

The degradation triggering fluid FL being applied to the plant propagation cell material 2 has the general purpose of initiating a hydrolysis of the polymer fibers of the plant propagation cell material 2. By planting of the plant propagation cells 1; 1.1; 1.2 this promotes root growth through the degrading plant propagation cell material. The degradation triggering fluid FL shall have the ability to initiate a hydrolysis reaction of the polymer fibers, preferably PLA fibers, of the plant propagation cell material 2. A fluid that is presently preferred to use as the degradation triggering fluid FL is in the form of an acetified Microfibrillated Cellulose gel (MFC-gel). In a practical exemplifying embodiment of the technology the degradation triggering fluid FL is prepared by mixing a fine ion exchanger powder in a specified proportion to the Microfibrillated Cellulose gel (MFC-gel). However, the technology is not restricted to the use of this specified fluid, but other present or future fluids having the same or similar properties may likewise be used.

Specifically, as the plant propagation cell material 2 of each plant propagation cell 1, 1.1, 1.2 is soaked with the degradation triggering fluid FL and a hydrolysis is initiated, the polymer fibers are degraded. These molten or partly molten polymer fibers initially provide the wet strength to the plant propagation cell material 2. Thus, the hydrolysis causes that the polymer fibers no longer hold the plant propagation cell material 2 together. As a result the plant propagation cell material 2 will easily break up, which has a positive effect on the root development of the plants P after planting.

The applying of the degradation triggering fluid FL to the plant propagation cell material 2 of the plant propagation cells 1, 1.1, 1.2 may be performed in various appropriate ways. One possible application method is very schematically illustrated in Fig. 4 and is performed by spraying a shower 11 of said degradation triggering fluid FL through a nozzle device 10 and onto the plant propagation cells 1, 1.1, 1.2. In an alternative, as schematically illustrated in Fig. 5, the application of the degradation triggering fluid FL to the plant propagation cell material 2 of the plant propagation cells 1, 1.1, 1,2 may be performed by lowering the plant propagation cells 1, 1.1, 1.2 fully or at least partly into a bath 16 of said degradation triggering fluid FL being provided in a receptacle 15. In both drawing figures 4 and 5 the method is shown being performed by applying the degradation triggering fluid FL to the plant propagation cell material 2 of the plant propagation cells 1, 1.1, 1.2 with the cells still being supported in the cell carrier 20. However, it will be realized that the application of the degradation triggering fluid FL to the plant propagation cell material 2 of the plant propagation cells 1, 1.1, 1.2 may equally well be performed with the cells 1, 1.1, 1.2 removed from the cell carrier 20.

With reference to the illustration in Fig. 6 laboratory tests will now be described, which have been performed in order to determine the practical results obtained by means of the present technology. Strips of plant propagation cell material 2 were cut out from a sheet of said material and these strips were soaked in different mixtures of acetified Microfibrillated Cellulose gel (MFC-gel) as well as in one reference fluid consisting of deionized water. The strips were then placed in a climate cabinet at room temperature and 100% Relative Humidity (RH). Test samples were then removed from the cabinet at different time intervals and were tested in a tensile testing machine in order to determine the weakening of the material. The diagram of Fig. 6 illustrates how the different strips having been soaked in the different fluids are weakened over time. As was indicated above, three different acetified MFC-gels were used in the tests in which the MFC was used as a carrier of an acidic ion exchanger powder in fine powder form. The mixtures were prepared by mixing different ion exchanger powders to the MFC-gel and by strong mixing by means of an appropriate device, such as a homogenizer.

The different mixtures that were used and that are represented in Fig. 6 are: A: Deionized water as reference, B: Mixture of 40ml MFC (0,5%) and 0,5g ion exchanger C: Mixture of 40ml MFC (0,5%) and lg ion exchanger D: Mixture of 40ml MFC (0,5%) and 5g ion exchanger.

From the diagram the different behavior of the test strips over time may be deducted although it should be emphasized that the test results are only used herein to exemplify the effects of the technology.

Other tests have shown that a degradation triggering fluid, such as an acetified MFC-gel, used according to this technology does not have any negative effect on the root development. In fact, comparative tests showed that such fluids did not have any such negative effect even if applied directly to the roots.

The proposed new technology has been described above with specific reference to presently proposed practical embodiments. However, it should be noted that the technology is in no way restricted to an embodiment where plant propagation cells are made having the form of a straight cylinder. The technology may be equally well suited for alternative embodiments where the cells are formed having other shapes, such as having a tapering form towards one of their ends. In the same way it is also possible to use other fiber compositions than the ones exemplified above as well as other propagation cell material degradation triggering fluids. It shall also be emphasized that although the technology has been described and illustrated with reference to an application for the propagation of forestry plants in nurseries it is in no way restricted to such a specific application. The basic principles of the invention may be applied to other types of plants as well as propagation facilities.

The present technology has been described in connection with embodiments that are to be regarded as illustrative examples thereof. It will be understood by those skilled in the art that the present technology is not limited to the disclosed embodiments but is intended to cover various modifications and equivalent arrangements. The present technology likewise covers any feasible combination of features described and illustrated herein. The scope of the present technology is defined by the appended claims.

Claims (9)

1. A method of controlling the future integrity of a fiber material plant propagation cell (1; 1.1; 1.2), wherein a plant propagation cell material (2) is formed of natural fiber and biodegradable polymer fiber, a plant propagation cell is formed from said cell material, plant substrate (S) is filled into the plant propagation cell, the plant propagation cell is positioned and supported in a cell carrier (20) and a plant (P) is introduced into the substrate of the cell, characterized in that prior to a planting of the plant propagation cell a degradation triggering fluid (FL) is applied to the plant propagation cell material, said degradation triggering fluid (FL) initiating a hydrolysis of the polymer fibers that by planting of the plant propagation cell (1; 1.1; 1.2) promotes root growth through the degrading plant propagation cell material.

2. A method according to claim 1, characterized by applying to the plant propagation cell material (2) of the plant propagation cell (1; 1.1; 1.2) the degradation triggering fluid (FL) in the form of an acetified Microfibrillated Cellulose gel (MFC-gel).

3. A method according to claim 1 or 2, characterized in that the degradation triggering fluid (FL) is prepared by mixing an ion exchanger powder in a specified proportion to the Microfibrillated Cellulose gel (MFC-gel).

4. A method according to any of claims 1-3, characterized by applying the degradation triggering fluid (FL) to the plant propagation cell material (2) of the plant propagation cell (1; 1.1; 1.2) by lowering the plant propagation cell at least partly (or fully) into a bath (16) of said fluid in a receptacle (15).

5. A method according to any of claims 1 - 3, characterized by applying the degradation triggering fluid (FL) to the plant propagation cell material (2) of the plant propagation cell (1) by spraying a shower (11) of said fluid through a nozzle device (10) and onto the plant propagation cell (1; 1.1; 1.2).

6. A method according to any of claims 1 - 5, characterized by applying the degradation triggering fluid (FL) to the plant propagation cell material (2) of the plant propagation cell (1; 1.1; 1.2) with the cell supported in the eel! carrier (20).

7. A method according to any of claims 1 - 5, characterized by applying the degradation triggering fluid (FL) to the plant propagation cell material (2) of the plant propagation cell (1; 1.1; 1.2) with the cell removed from the cell carrier (20).

8. A method according to any of claims 1 - 7, characterized by forming the plant propagation cell (1; 1.1; 1.2) having the form of a straight cylinder.

9. A method according to any of claims 1 - 7, characterized by forming the plant propagation cell (1; 1.1; 1.2) having a tapering form towards one of its ends.