Method of lengthening the durability a flower, and plant assembly with lengthened durability.

DESCRIPTION Field

The invention concerns a method and means for lengthening the durability or for maintaining the life and/or of the growth of a plant, in particular a flower bearing plant e.g. in cut state, i.e. a state in which the stem of the flower or plant part has been cut off.

Background

It is desirable to lengthen the durability of (cut) flowers or plant parts while it is also desirable to maintain the life and/or the growth of such flowers or plant parts, e.g. for the purpose - e.g. in the environment of a greenhouse - of continuing their growth or at any rate their life, but without the need to make use of the flower or plant roots etc. with which the flowers or plant parts are connected under more natural conditions but which are now cut off from them. With respect to a flower bud or buds, similar desires may apply both for cut flowers and for flowers which still have their roots or bulb(s).

In the following the term "plant part" will be used to designate parts of both complete plants and of parts of plant that have been cut off from a complete plant. In the following, a number of times the term "cut flowers" will be used, but it is to be understood that all flowers or plant parts in whatever form in cut off state (from the root, bulb, tuber etc.) will be included within this term "cut flowers".

Flowers may be included in a bouquet or flower arrangement. Such flowers normally last for a few days to a few weeks. In order to improve the durability, additives, e.g. including fertilizing and/or bactericidal (biocidal) materials are added to the water In the case of flowers having a weak stem, the stem may be strengthened, e.g. using a wire.

In the Netherlands, there is a significant market for the production of cut flowers, while most flowers are traded via a flower auction.

The aging or wilting of cut flowers can be caused by the fact that they absorb too little or contaminated water and/or nutrients and minerals via the cut stem surface. An important cause of

this is biofouling, i.e. the formation of a layer of microorganisms on the surfaces where the nutrients are located. A freshly cut surface of a flower stem in combination with water at room temperature is precisely a typical surface where biofouling can appear rapidly.

WO 89/ 07392 discloses a method wherein a cut-off end of a plant stem is put in a sealed container. A hollow fiber with a porous wall is used to supply water to the container. The ends of the fiber are located in the sealed-off part and outside the container the fiber is looped through water. The water enters through the porous wall of the fiber and flows to the container with the cut-off end of the stem. The wall has a porosity that blocks micro-organisms from entering the fiber. Thus, wilting is delayed, but the construction with a fiber and a sealed container makes this solution very complex. The construction is also cumbersome because the combination of the need to provide for sufficient transmission of water through the wall of the fiber and the need to provide a fiber of sufficient thickness to avoid breaking result in a relatively long fiber.

US 3,842,539 discloses placing the cut-off end of a stem in a tube with a ion exchange resin mass. The tube seals of the stem so that water flows to the stem only through the ion exchange resin mass. This reduces physiological blockage of the water conducting tissue and aids in the retention of fresh weight.

FR 2256717 discloses placing a film of water soluble conservative on a plant stem by means of spraying or dipping in a bath. When the stem is placed in a vase, the conservative dissolves into the water of the vase where it helps to suppress the growth of micro-organisms.

Summary

Among others it is an object to create a simple solution for improvement in the durability of cut flowers.

Among others it is an alternative object to create an improvement in the durability of cut flowers in any stage of the production and/or usage process, i.e. from the moment when the flowers are

"harvested" by cutting them off from the rest of the plant. After all, the process of aging or wilting starts at that same moment.

A method of processing a plant part is provided wherein membrane is placed on a water transmitting surface of the plant or plant part. Use may be made of membrane technology which is

also used, among others, for purifying water but which also has medical applications. In this context, the term 'membrane' refers to materials having e.g. (micro)pores that are smaller than bacteria but larger than water molecules (and possible additives) so that the water is admitted to the flower stem but not the bacteria. That is, the membrane is water transmitting and micro-organism blocking. The part of the membrane that is on the water transmitting surface acts to block microorganisms while it transmits water. The membrane is placed in such a way that water transmitted by the water transmitting surface will be transmitted substantially through the membrane where the membrane is placed on said water transmitting surface. The water is transmitted substantially though the membrane in the sense that except for unavoidable leakage the water reaches the water transmitting surface only through the membrane part that is on the water transmitting surface. A separate surface for letting through water distant from the plant is not indispensible to provide for protection against micro-organisms. Thus, a constructively simple and compact protection of the plant is obtained.

According to one aspect a method is provided for lengthening the durability or for maintaining the life and/or growth of a plant part e.g. in cut state, i.e. in a state in which the stem of the flower in question has been cut off and the stem therefore has a cut surface via which the cut-off flower can absorb, e.g. a liquid such as water from a reservoir such as a vase, said method preferably including the application of the membrane to the flower stem and/or flower bud or buds in such way that liquid and/or moisture is transmitted via the membrane. In this way, at least part of the liquid flowing via the membrane is supplied to the flower (stem) while bacteria etc. are retained by the membrane and cannot get access to the stem and/or flower material and cause damage.

The same may be done for a bud or buds which may be covered or coated by a membrane layer. The bud membrane-just like the stem membrane coating or other membrane configurations- will stop or at least substantially reduce damaging environmental influences like bacteria, toxic gases etc., however, without -due to the membrane function- the normal "respiration" (i.e. the exchange of moisture from and to the buds) of the flower buds.

There are various ways of applying suitable membranes. In an embodiment the membrane may be applied by immersing at least the relevant plant surface in a liquid membrane substance (e.g. "dip coating") or by spraying at least the cut surface with a sprayable (e.g. mist forming) membrane substance. In an embodiment spraying or immersion may be applied to the flower bud(s) by means of spraying of a bud with a membrane forming liquid substance or immersion of the bud in a membrane forming liquid substance.

In another embodiment, the membrane may be realized as a rod or tube that is inserted partially into the plant stem. That is, such a rod or tube is placed on a surface of the plant inside the stem. This surface may be realized by the act of insertion. The membrane may e.g. be inserted into the stem via the cut surface. In this option, the liquid is guided to the interior of the stem via the part not inserted into the stem and thus extending outside the stem. In this membrane configuration, the membrane can promote the flow (e.g., flow velocity) of the liquid to and through (part of) the stem. Of course, insertion may leave some remaining part of the cut surface open to external water, but because the contact surface between the rod or tube and the interior surface of the stem is much larger, this hardly affects water supply. In addition, the membrane can mechanically strengthen the stem and thereby fulfill the function of an e.g. metal stiffening wire, which may be used for cut flowers.

A plant assembly is provided for that comprises a plant, cut off at the stem for example, with a protective membrane placed on a water transmitting surface of the stem. In such an assembly the useful life of the plant is extended. The membrane may take the form of a coating that is contiguous with the water transmitting surface, i.e. not something like a foil wrapped around the plant. Such a coating can be obtained by immersion or spraying for example. Thus a simple and easy to produce assembly is provided for. In an other embodiment the membrane make take the form of a rod or tube inserted into the plant stem.

A protection device may be provided in the form of a rod or tube that comprises the membrane and has a diameter that is less than that of the stem. In the case of a tube, the tube may be sealed at one end, for example the end that is inserted into the plant stem, to prevent water from reaching the plant directly through the tube. In an embodiment, the tube shaped membrane may be sealed at both ends and a cavity between both ends may be filled at least partially with substances such as a fertilizing and/or bactericidal substance.

Brief description of the drawing

In the following, the invention will be explained further with reference to some exemplary embodiments which schematically are shown in:

Figure 1 in which an exemplary embodiment is shown of a membrane inserted into the cut surface;

Figure 2 in which an exemplary embodiment is shown of a membrane that is applied around a part of the stem

Figure 3 in which an exemplary embodiment is shown of a membrane applied essentially at the site of the cut surface.

Detailed description of exemplary embodiments

Figure 1 shows a membrane 1 in an embodiment suitable for being placed on the cut surface of a stem 3. The membrane 1 could be a rod shaped membrane that is suitable in shape and material - e.g. ceramic (AI ₂ O ₃ ) -- and dimensions for being inserted into the stem 3 or, as shown in the figure, in the cut surface 2. From the membrane 1, a part Ia extends into the stem 3 while a part Ib extends outside it and may be in contact with liquid 4 (normally mainly water) in a container 5 (e.g., a vase, shown schematically). Via the very narrow (micro)pores of the membrane, the liquid 4 can, and any bacteria etc. cannot, enter into the interior of the membrane 1 and therefore to the interior of the stem. As a result of the thus-obtained clean supply of liquid to the stem 3 it may be expected that the durability of the flower(s) (not shown) connected to the stem 3 and of any leaves will be lengthened.

Preferably, as Figure 1 shows, instead of a solid rod shaped membrane, use is made of a tubular membrane, e.g. also of ceramic material, which is arranged to be inserted into the stem or into the cut surface, said tubular membrane being sealed, at least at one end. The transport of liquid is facilitated and thereby promoted by a cavity 6 present as a result of the tubular shape. The bottom side or top side of the tubular membrane should be closed in order to prevent (possibly bacterially contaminated) liquid from getting access to the stem via the ends, which could seriously impair the purifying effect of the membrane. The material used to seal the tubular membrane 1, like the material of the tubular membrane 1 itself, is preferably a material with microporous properties so that only the liquid 4 can enter via the pores.

The tubular membrane shown in Figure 1 is even sealed at both ends. The hollow part between them may be at least partially field with a quantity of e.g. a fertilizing and/or bactericidal substance 7 which can go into solution in the liquid flow and thus be supplied to the stem 3, the flower (not shown) and/or the leaves.

Figure 2 shows an exemplary embodiment of a membrane applied around a part of the stem, where a substantial part of the stem and the entire cut surface has been surrounded by a more or less sack- shaped foil or coating 8 which may be fabricated separately from the stem 3 and the cut surface 2. In an embodiment the membrane is applied directly - e.g. by spraying or immersing a substantial part of the stem -to the stem 3. Thus a coating layer is formed that first contiguously to the stem and the cut. For example, the membrane material in this case is a (preferably hydrophilic) non- woven membrane material based on, e.g. a (co)polymer suitable for this purpose, e.g. silicone (polysiloxane), PDMS (polydimethylsiloxane), PAN (poly aery lonitrile), or PSU (poly sulf one).

In the embodiment shown in Figure 2, it will, during practical use, be necessary for the upper edge 9 of the membrane sack 8 to be positioned above the liquid level 10 in order to assure that the liquid 4 can access the stem and - in particular - the cut surface 2 exclusively via the membrane sack 8. If, as stated in the lines above, the membrane 8 is obtained by immersion or spraying of the bottom part of the stem 3 including the cut surface 2, it will not be necessary, or at least less necessary for the upper edge 9 of the membrane 8 to extend above the liquid level 10, for it may be assumed that the liquid 4 may not be able to reach the cut surface 2 between the inner side of the membrane 8 and the outer side of the stem 3, as the membrane layer 8 is then always applied directly, e.g. by immersion or spraying, to the surface of the stem 3.

Finally, Figure 3 shows an exemplary embodiment where a membrane 11 is applied essentially at the site of the cut surface. In this case the membrane 11 can also be produced by e.g. immersing the bottom end of the stem 3, especially the cut surface 2, in a membrane substance. As can be seen in the figure, the membrane substance preferably covers the entire surface of the cut, to form a coating on the entire surface of the cut. Optionally the membrane substance may also cover part of the stem adjacent the cut. Preferably, the coating layer is contiguous with the surface. Such a membrane substance may, as stated above, be based on one of the above-named (co)polymers. After immersion or spraying the material may dry, i.e. a solvent may evaporate from the material, to form a solid coating on the stem 3. Preferably, a material is used that, once deposited on the plant, is sufficiently insoluble in water in the sense that the coating will remain on the plant during the plants' useful "life" while it is placed in water and kept in a vase, e.g. for at least a week.

In an embodiment the membrane of figure 3 may be applied in a single spraying or immersion step. Alternatively, application of the membrane may involve a plurality of successive spraying and/or immersion steps. Dipcoating or spraycoating may be preferred in view of fast and simple processing.

Preferably a coating material is used in the membrane that provides for good transportation of water and ions, enabling the flower to receive enough water and nutrients. In the case of a membrane on a cut surface of the stem it is also preferred that the membrane, once deposited, is sufficiently insoluble in water that it remains effectively present during the useful "life" of the plant, e.g. for a week or a month. Preferably a coating is selected that blocks passage of air through the coating. This helps to prevent blocking of the capillary channels of the flower by air inclusion.

In an embodiment a coating with anti-biofouling properties is provided for. In an embodiment bacterium resistant properties are realized, e.g. by including colloidal silver in the coating material; In an embodiment fungicidal properties are provided for, e.g. by means of using natamycin in the coating material.

Apart from the materials mentioned in the preceding, many alternative materials may be selected for use in immersion or spraying the cut stems and/or the flower bud(s). Examples of suitable biopolymers for forming a membrane layer are: (optionally modified) starch, alginate, carrageenan, gelatine, hydroxycellulose, methylcellulose, sodium carboxymethylcellulose , lignine, lignosulfonate sodium salt. Examples of synthetic polymers for forming a membrane layer are polyacrylamides, polyacrylamido-2-methyl-propanesulfone acid (sodium salt), polyacrylic acid (sodium salt), polyethylene-maleinic acid anhydrid, polymethyl vinyl ether-maleinic acid, polymethyl vinyl ether-maleinic acid anhydride, hydroxyethyl methacrylate, polymethacryl acid (sodium salt), polyallylamine (hydrochloride), polydiallyldimethylammonium chloride, polyethylene imine, polyethyl-oxazolin, polymethylvinylether, polystyrene sulfonate (sodium salt), polyvinyl sulfate (sodium salt), polyvinyl alcohol, polyvinylpyrolidon, polyethylene glycol and its many copolymers. As far as these materials are water soluble, additional measures may be taken, such as the addition of cross-linking agents or other solution agents or addition of further coating layers, or the membrane layer may be deposited with a thickness that ensures that the membrane will not dissolve so far that it becomes ineffective before the end of the intended useful life of the plant, e.g. not within a week.

The matrix material of the membrane may comprise water swellable polymer, either a biopolymer or a synthetic polymer that can be deposited from a solution or suspension. Optionally a binary system could be used, with a monomer or polymer solution and a cross-linking agent that is added after the monomer or polymer solution is applied to a surface of the plant by a second spraying or immersion step, or mixed with the monomer or polymer solution shortly before the monomer or

polymer solution is applied to the plant. In another embodiment a multilayer coating may be used, which may be applied in successive steps, each involving immersion and/or spraying with a respective material. Thus for example one or more water soluble membrane layers may be applied first, followed by application of a not water soluble layer, surrounding the water soluble layer.

In an embodiment a latex-type liquid may be used to apply the membrane, that is, a polymer dispersion with globules of film forming material, such as a poly-acrylate. A layer of latex-type material may be deposited with a thickness that allows water to pass through the layer. This type of layer may be used to realize the membrane itself or it may be used as an additional coating layer on top of the membrane layer.

In an embodiment a cross-linking agent such as a dialdehyde may be added to the membrane forming material. This may serve to cross-link polymers like cellulose or starch. In another embodiment metal ions may be added as an agent. Calcium made be used to interconnect alginates or iron may be used to interconnect polyacrylates for example.

Referring to the adherence to the flower stem or bud surface, the following could be noted. The roughness of the flower stem or bud surface, the favourable polymeric adsorption enthalpy at the relevant surfaces (i.e. numerous attachment points per surface area) and the various possible interactions (hydrophilic, hydrophobic and ionogenic) all assist in attaching to the flower stem or bud surface. Many of the mentioned polymers are applied in adhesives. The adhesive properties could still be improved by addition of e.g. latex and/or resins.

Flower buds as susceptible to influences from their outside environment. Flower buds can be protected against such influences by coating by means of immersion and/or spraying the buds. In particular micro-organisms like fungi may affect the buds. Besides, a high concentration of ethene may occur when many cut flowers are close together, e.g. in the auction- mart of flower shop. A coating having selective properties is able to protect the buds against those influences. Protective coatings should have the following properties: • Preferably good transport or adsorption properties for ethane are realized, e.g. by means of applying STS (silver thiosulphate), Ag ⁺ or AgBF ₄ as an active component in the coating material;

• In an embodiment fungicidal properties may be provided for e.g. by applying natamycin and/or a hydrophobic in the coating, preventing fungi to grow.

Coating by means of spraying may be preferred due to its fast and simple way of processing. It is preferred the coating to be colorless or to have the color of a plant part on which it is applied.

According to another preferred embodiment, the membrane at least partially surrounds the stem or at least the entire cut surface. For example, the membrane can cover the stem in such way that in operation, e.g. when the flowers are placed in a vase, a liquid surrounding the stem can reach the stem exclusively via the membrane, e.g. by means of a membrane coating over a substantial part of the stem (including the cut surface), so that the liquid can reach the stem exclusively via the coating. In another form, a membrane may be applied primarily on or against the cut surface, which requires less membrane material.

Among others, it is an alternative object to maintain the life and/or the growth of such flowers or plant parts, e.g. for the purpose of continuing their growth or at any rate their life, but without their natural root systems (or bulbs, tubers etc.).

It is emphasized once more that application of membranes for stems is not limited to lengthening the durability of (cut) flowers or plant parts but also extends to maintaining the life and/or the growth of such flowers or plant parts, e.g. for the purpose of continuing their growth or at any rate their life, but without their natural root systems (or bulbs, tubers etc.). In this connection, the proposed membranes or membrane-containing components may be viewed as root-replacing elements which can result, e.g. in the production of flowers or plants in greenhouses, in substantial advantages, due to the fact that the function of the plant roots etc., which after all are intended (as opposed to what is frequently the case in modern greenhouses) to be in contact with ("full") soil under natural conditions, can be taken over by membranes or elements containing membranes, which then can act as artificial roots. Membranes may also, if desired, be used in combination with a (natural) root system, e.g. in the form of a type of infusion which may be applied (or introduced) between the cut surface and the flower or into the stem. The membrane element may also fulfill the function of an "artificial root" for cut flowers etc. which are part of flower arrangements, or which - quite commonly - are placed in a vase.