GB2325138A - Suspensions for plant propagation material - Google Patents

Abstract

A suspension suitable for use in the storage and distribution of plant propagation material, wherein said suspension comprises plant propagation material and a water soluble or water dispersible polymer and, when applied to a growth medium, migrates into the growth medium. The water soluble polymer may comprise a polyvinyl alcohol.

Description

SUSPENSIONS The present invention relates to suspensions suitable for the storage, transportation and distribution of plant propagation material.

Plant propagation material includes propagules, plant parts, plant tissues and plant organs which are capable of growing or regenerating into a plant, for example seeds, spores, somatic embryos, callus material, cells or cell aggregates, microcuttings, cuttings, bulbs, tubers, corms, rhizomes, stolon and fruit. Today the seed business is highly competitive. The performance of seeds has a direct effect on competitive position and profitability. It is desirable to sow seeds in a manner which will achieve close to 100W germination. Anything less than 100% germination increases costs and reduces profits. The failed areas often need to be re-sown. This can be very labour intensive and therefore expensive. It is an aim of the present invention to provide a means of storing, transporting and planting plant propagation material, including propagules such as seeds, which results in a high degree of sowing precision and/or emergence or germination.

Damage to seeds is a major cause of low emergence or germination rates. It is known that seeds, especially small and/or delicate seeds, are subject to mechanical damage during handling and transportation. Seeds can be so badly damaged that they are unable to grow and develop into healthy plants. It is an aim of the present invention to provide a means of storing, transporting and distributing plant propagation material including propagules such as seeds, which reduces mechanical and physiological damage.

Seeds, if they are small, may be pelleted with, for example, clay mixtures which facilitates sowing of the seeds and facilitates handling (DE-A-2551579). The seeds can, however, be damaged during the pelleting process This reduces the percentage of seeds which are able to germinate and/or develop into healthy plants.

It is an aim of the present invention to provide a means of storing, transporting and distributing plant propagation material, including propagules such as seeds which facilitates handling and which reduces damage to the plant propagation material.

At present, pre-germinated seeds such as those described in US-A-5585536 and .US-A-5522907 will only survive for a limited period of time between germination and planting. This time period depends on the nature of the seed and the storage conditions. It is a further aim of the present invention to provide a means of storing pregerminated seeds for longer periods of time and/or reducing the percentage of pre-germinated seeds which fail to develop into healthy plants.

The present invention provides an aqueous suspension suitable for use for the storage, transport and distribution of plant propagation material, wherein said suspension comprises a water soluble or water dispersible polymer and, when applied to a growth medium, migrates into the growth medium.

Suitable water soluble polymers include polyvinyl alcohol (PVOH), hydroxypropylmethylcellulose and other modified celluloses, polyethylene oxide, natural gums such as alginate or xanthan gum, sugars, starches or mixtures thereof. Preferably the suspensions of the invention comprise polyvinyl alcohol (PVOH). Suitable polyvinyl alcohols include partially hydrolysed polyvinyl acetate; they typically have 88 to 89 hydrolysis (this degree of hydrolysis is typical for cold water soluble PVOH).

Suitable polyvinyl alcohols include Alcotex (registered trademark) and Mowiol (registered trademark).

There are several advantages of using suspensions comprising PVOH. PVOH is biodegradable; it is broken down by microorganisms. PVOH can act as a wetting agent.

The suspensions may comprise an osmotic agent to control the level of hydration of the plant propagation material. For example the hydration of suspended material such as propagules, e.g. seeds, may be controlled to reduce the speed of, e.g. germination. Osmotic agents include glycols such as polyethylene glycol. Dilution of such suspensions, for example prior to application to a growth medium or afterwards by watering in would dilute the osmotic agent and facilitate normal hydration of the material and subsequent germination or growth.

The suspensions can additionally comprise an electrolyte. The presence of an electrolyte may reduce the amount of water taken up by the plant propagation material; this may reduce the rate of growth. The choice of electrolyte will depend on the nature of the plant propagation material and the nature of the growth medium.

The suspensions may also comprise a substantially water insoluble particulate material. The particulate material is generally substantially inert to water and to the growing medium. A light reflective material may be used in order to reduce transmission of light to suspended plant propagation material. Particulate titanium dioxide is preferred. This and other particulate materials may, depending on, for example, the concentration used and the particle size, affect the viscosity of the suspension. The viscosity of the suspension is, in any event, preferably adjusted to avoid substantial "settling out" of the particulate material.

The amount of water soluble or water dispersible polymer present in the suspensions of the invention will depend on the size and density of the plant propagation material and the method used to apply the suspension to growth medium. The suspensions of the invention typically comprise from 2 to 35% by weight of a water soluble or water dispersible polymer based on the total weight of the suspension. Preferably the suspensions comprise from 10 to 25% by weight of a water soluble or water dispersible polymer based on the total weight of the suspension.

Preferably the suspensions of the invention additionally comprise a marker, for example a colourant or a fluorescent additive. Suitable colourants include water soluble dyes or pigments. The concentration of marker will generally be low, e.g. 1% or less by weight.

The presence of the colourant or fluorescent additive can be used to differentiate different suspensions. The colour of the suspensions can therefore be used to identify suspensions containing different varieties of plant propagation material. In addition, the colour of the suspensions enables the user to see the suspensions when they have been applied to the growth medium. This enables the user to monitor reliable application of the plant propagation material.

The suspensions of the present invention may additionally comprise an additive to enhance the ability of the plant propagation material to emerge or germinate and/or grow into healthy plants. Suitable additives include pesticides, growth promoters, growth regulators, nutrients and bird repellents. Preferably the suspensions comprise at least one of a pesticide, a growth promoter, a growth regulator, a nutrient and a bird repellant.

The suspensions of the invention generally act as a carrier and a wetting agent. When a quantity of suspension is placed on the surface of the growth medium the suspension wets the surface of the growth medium. A wetting agent can be added to the suspensions of invention to promote adequate wetting of the surface of the growth medium. Preferably, the wetting agent is non-ionic.

The preferred viscosity of the suspensions of the present invention depends on the plant propagation material. The viscosity should preferably allow the plant propagation material to be held in suspension and facilitate application of the suspension to the growth medium. If suspensions of too low a viscosity are used the concentration of plant propagation material in suspension may be difficult to control as the plant propagation material may sink to the bottom of the suspension or may float. If the viscosity of the suspension is too great the suspension generally does not flow sufficiently readily to permit easy application to the growth medium.

The required density of the suspensions will depend upon the density of the plant propagation material in suspension. It may be advantageous to adjust the density of the suspension to a value approximately equal to that of the plant propagation material.

The suspensions of the present invention act as thermal buffers. The suspensions insulate the plant propagation material contained within them from sudden changes of temperature. The suspensions may therefore be used for storing plant propagation material which is sensitive to sudden changes in temperature.

The concentration of the plant propagation material in the suspensions can be varied to ensure reliably the presence of a predetermined amqunt of plant propagation material in an applied volume. For example one or two propagules such as seeds in an applied volume.

The preferred concentration of plant propagation material will depend, for example, on the size of the plant propagation material.

It is also within the scope of this invention to store and transport plant propagation material including propagules such as seeds in a concentrated suspension which can be diluted with water or more of the suspension medium prior to use.

The suspensions of the present invention can be used with any suitable plant propagation material for example, propagules, including seeds and spores. The suspensions are particular suitable for the storage, transportation and distribution of small seeds and/or high value seeds.

However, use of the suspensions of the invention is not restricted to small seeds and/or high value seeds. By "small seeds" is meant seeds of less than 500 microns. The seeds may be uncoated or coated before being suspended in the suspensions of the invention.

It is often desirable to plant only one or two items of plant propagation material, including propagules such as seeds in a given area. Using traditional methods the separation of, for example, propagules is labour intensive and can damage the propagules. Plant propagation materials, including propagules such as seeds separate when placed in the suspensions of the present invention.

Generally, mixing of the suspension is not required to separate the materials. Therefore, for example, the propagules can be separated without mechanical damage to them. The suspensions of the present invention can be used with plant propagation material including ungerminated or pre-germinated propagules.

The suspensions can be stored in transparent or nontransparent packaging. The suspensions themselves are generally translucent or transparent. Germinated propagules should preferably be stored in the absence of light to reduce further growth. Suspensions containing germinated propagules are therefore preferably stored in non-transparent packaging.

Preferably the packaging should be moisture impermeable. The water content of some of the suspensions of the invention, for example suspensions comprising PVOH, will equilibrate with the water content of the atmosphere.

An increase in the moisture content of the suspension may increase the rate of growth of the plant propagation materials, including propagules such as seeds or damage them. The suspensions may typically be stored in damp atmospheres such as greenhouses and garden sheds. It is therefore preferable that the suspensions are packaged in moisture impermeable packaging.

The suspensions can be distributed onto the growth medium in any suitable manner.

The present invention also provides a kit for producing suspensions of the invention containing plant propagation material, including propagules such as seeds of the user's choice. Such a kit may include, for example, a solution or dispersion of the water soluble or water dispersible polymer, ready for use or requiring dilution before use to yield a concentration as hereinbefore described, or the water soluble or water dispersible polymer itself, for example in the form of granules, for dissolution in water prior to use. Additional ingredients, as hereinbefore described, may be included in the solution or with the solid water soluble or water dispersible polymer.

Plant propagation material, including propagules, such as seeds, may be suspended in the solution of the water soluble or water dispersible polymer or (less preferably) may be mixed with the solid polymer prior to its dissolution in water. The kit may also include means for applying the suspension thus obtained to a growth medium.

Such means may include a syringe or a flexible container, for example, a plastics bag, with a nozzle through which the suspension can be expressed.

The suspension according to the invention may be dried to provide a solid product comprising plant propagation material, a water soluble or water dispersible polymer, and, optionally, other ingredients as hereinbefore described. The solid product, and a process for preparing it by drying the suspension, both constitute features of the invention. The invention accordingly provides a composition comprising, in solid form, plant propagation material and a water soluble or water dispersible polymer obtainable by drying a suspension according to the invention. Individual droplets of suspension each containing plant propagation material, for example a propagule such as a seed may be dried: for example such droplets may be applied to a substrate such as glass and then dried. Alternatively a layer of suspension may be applied to a substrate such as glass prior to drying: the thickness of the suspension on the substrate may be adjusted by, for example, using a doctor blade, the film thus obtained may be cut into pieces each containing plant propagation material. Drying may be effected, for example, by air drying at ambient temperature. The dried, coated plant propagation materials thus obtained preferably each contain a single item of plant propagation material, eg. a propagule such as a seed and are preferably of a size which is convenient for handling. The dried, coated plant propagation material is preferably packaged in a water impermeable outer container. The drying step should be conducted, for example, at a suitable temperature and rate of water removal to avoid damage to the plant propagation material.

The present invention is illustrated by the following Examples.

Example 1 A solution comprising 20% by weight of Alcotex 78 (a cold water soluble polyvinyl alcohol) based on the total weight of the solution was produced by dissolving Alcotex 78 in hot water and then cooling the resulting solution to room temperature.

Pansy seeds were added to the cooled solution to provide a concentration of 10 seeds per ml and the mixture was gently stirred.

The suspension was allowed to settle. Then about one drop (about 0.1 cc) of the suspension (containing 1 seed) was transferred by pipette to a plug of growth medium (John Innes No. 2 potting compost). The procedure was repeated. Each plug of growth medium was watered twice a day for 10 days. After this time each plug had become a viable plant.

Example 2 A suspension containing pansy seeds was produced using the method described in Example 1. The suspension was stored at room temperature (10 to 250C) for six weeks. The suspension was transferred to the growth medium in the manner described in Example 1. After watering twice a day for 10 days each plug had become a viable plant.

Example 3 A suspension containing pansy seeds was produced using the method described in Example 1. Some seeds were singulated before drying using a pipette to produce discrete droplets on a glass plate, each droplet containing one seed. In a second procedure the suspension was poured onto a glass plate and the resulting film was air dried at ambient temperature. The seeds were then singulated after drying by cutting out blocks each containing one seed. The seeds were sown in plugs in standard conditions. After watering twice daily for 10 days each plug had become a viable plant

Claims (14)

1. A suspension suitable for use in the storage and distribution of plant propagation material, wherein said suspension comprises plant propagation material and a water soluble or water dispersible polymer and, when applied to a growth medium, migrates into the growth medium.

2. A suspension according to claim 1 wherein the water soluble polymer comprises a polyvinyl alcohol.

3. A suspension according to claim 1 or 2 which additionally comprises a colourant or fluorescent additive.

4. A suspension according to any one of the preceding claims which additionally comprises at least one of a pesticide, a growth promoter, a nutrient, a growth regulator and a bird repellant.

5. A suspension according to any one of the preceding claims wherein the plant propagation material is a propagule.

6. A suspension according to claim 5 wherein the plant propagation material is a seed.

7. A suspension according to claim 6 wherein the seed is a pre-germinated seed.

8. A suspension according to claim 7 which can be stored at ambient temperature for five weeks without a substantial deterioration in emergence after planting.

9. A suspension according to any one of the preceding claims which comprises a water insoluble particulate material.

10. A kit for the preparation of a suspension according to any one of the preceding claims which comprise a water soluble or water dispersible polymer, solid or in aqueous solution, and means for applying the suspension to a growth medium.

11. A composition comprising, in solid form, plant propagation material and a water soluble or water dispersible polymer, obtainable by drying a suspension according to any one of claims 1 to 9.

12. A suspension according to claim 1 substantially as hereinbefore described.

13. A kit according to claim 10 substantially as hereinbefore described.

14. A composition according to claim 11 substantially as hereinbefore described.