WO1992017055A1

WO1992017055A1 - Method of and apparatus for separating plant material

Info

Publication number: WO1992017055A1
Application number: PCT/GB1992/000554
Authority: WO
Inventors: William Peter Billington; Peter Michael Grundon
Original assignee: British Technology Group Ltd
Priority date: 1991-03-26
Filing date: 1992-03-26
Publication date: 1992-10-15
Also published as: GB9106422D0; GB9206654D0; GB2257007A

Abstract

Apparatus for separating plant material comprises a set of blades (16) protruding upwardly from a circular base plate (12), and a set of dividing rods (20) projecting downwardly from a supporting ring (18). In use, a container of plantlets is placed on a dish (9) between the base plate (12) and the ring (18), and the ring (18) is moved downwardly, carrying the rods (20) downwardly into the plant material, and forcing the blades (16) upwardly into the plant material. The ring (18) is then rotated relative to the base plate (12), the spacing and positioning of the rods (20) and blades (16) being such that the rods and blades interpenetrate and pass between each other during the rotation. The rotary movement effects separating of the plant material by a combined action of teasing apart, splitting and cutting, of the plant material.

Description

METHOD OF AND APPARATUS FOR SEPARATING PLANT MATERIAL

The present invention relates to a method of and apparatus for separating plant material, and relates in particular, but not exclusively, to methods and apparatus for use in micropropagation, particularly the dissection and separation of a complex mass of plantlets which have been grown in a nutrient medium during micropropagation, and need to be separated into plantlets for further propagation. ^'

Micropropagation of plants involves the use of the techniques of plant tissue culture and the application of these techniques to the propagation of plants. At its simplest, micropropagation consists initially of excising small pieces of actively growing tissue, normally shoot tips from an adult plant. Then, under sterile conditions, the pieces of tissue are transferred to a nutrient medium which supports plant growth. Dependent upon the species, the ingredients in the medium are chosen to encourage a particular form of plant growth, e.g. extension of a single shoot or development of a cluster of shoots. After a suitable period of growth the plantlets are cut into smaller pieces for regrowth in accordance with the preferred dissection strategy for the particular plant form. This stage, the multiplication stage, is repeated several times before a batch of plantlets is grown into viable plants. This final stage is that a batch of plantlets must be weaned from the axenic conditions in which they have existed within the laboratory, into viable, rooted plants capable of survival in conventional horticultural or agricultural environments.

The growth of plants in this way from tissue culture (micropropagation) is a technique which can produce large numbers of genetically identical plants, perhaps possessing a desirable quality such as disease resistance, in a short time. The tasks of dissecting and transplanting such plants are labour intensive and repetitive, and the gains in speed, sterility and labour costs which could be achieved by the use of robots make automation an attractive prospect for the fast-expanding micropropagation industry.

The techniques used at present are labour intensive and one operation which is repeated frequently is the cutting of plant material during the multiplication stage, to produce new, small, plantlets for further growth. For most plants, the current manual technique is to remove a plant from nutrient material in a container, hold the plant by forceps on a sterilised card by one hand, and cut the required portion of plant by strokes of a scalpel, by the other hand. Some trimming of unwanted portions of foliage and roots may be needed. The selected cut portion of plant is then transferred by forceps to fresh nutrient medium, which is in the nature of a gel, and the cutting is then placed upright in the soft nutrient medium.

Whilst many house plants form shoot clusters in micropropagation, the methods of dividing these clusters during multiplication show detail differences in response to the morphology of the specific variety and its susceptibility to damage. Usually the upper foliage is cut off to encourage the formation of new shoots, and the important differences in dissection strategies lie in the method chosen for separation of the basal portion. For example, with Syngonium the mass of closely bound developing shoots is cut into several pieces using the position of the more mature shoots as a guide in choosing the dissection planes. With other plants, for example Calathea pendula, the plantlets grow to have more recognisably separate shoots than is the case with

Syngonium. It is observed that a human operator effects the division of plant material into fresh plantlets by teasing apart the tangled mass of plantlets with the scalpel and forceps, sometimes dividing plant material by prizing apart shoot portions of the plant, and only sometimes cutting the base portions of the plants to divide the plant material. The reproduction of this human operation by an automated or semi automated robotic system would be difficult and expensive to achieve, due to the intelligent assessment which the human makes when handling the varying plant material.

It is an object of the present invention, at least in preferred forms, to provide a method of separating plant material for use in micropropagation, particularly suitable for plants of the shape and structure such as calathea pendula, by a relatively gentle action which produces separation and dissection of plantlets along natural lines of division in the mass of plant material.

According to the present invention there is provided a method of separating plant material comprising: introducing into a mass of plant material two sets of spaced apart dividing elements, and producing relative movement between the sets of elements in a direction transverse to the general direction of growth of shoots of the plant material in such a manner that elements of each set interpenetrate and pass between elements of the other set.

In a preferred form the method includes presenting at a work station a mass of plantlets growing in a nutrient medium extending generally in a plane, introducing the dividing elements into the mass of plantlets in a direction or directions transverse to the plane of the medium, and producing the said relative movement between the sets of elements in the general plane of the medium. Although it is possible that both sets of dividing elements may be introduced into the plant material from one direction, for example being inserted into the mass of plant material in the region of the roots of the plant material, it is particularly preferred that the method includes introducing one set of elements into the plant material in a first direction, and introducing the other set of elements into the plant material in a second direction opposed to the first direction, the two sets of elements extending in the two opposed directions to an extent such as to overlap in the plant material. Preferably the elements overlap throughout substantially the whole region in which they extend into the mass of plant material. This allows full interpenetration of the elements of the two sets into the plant material, and produces particularly effective separation of the plant material during the said relative movement between the sets of elements.

Although in its broadest aspects, the invention may provide that the two sets of elements are of generally the same form, it is particularly preferred that the method includes engaging the plant material by one set of elements which are relatively blunt to effect separating without a cutting action by those elements, and engaging the plant material by the other set of elements which are relatively sharp to effect separating by an action including a cutting action by those elements. In order to avoid or reduce damage of shoots, it is particularly preferred that the method includes introducing the set of blunt elements into the plant material through the region of shoots of the plant material, and introducing the set of sharp elements into the plant material through the region of base portions of the plant material. It has been found that for some forms of plant material such as syngonium, the multiplication process is not unduly harmed by cutting the plant material from the top, and that any damage to shoots is acceptable in the subsequent regrowth. However for other types of material such as calathea pendula, damage of shoots has a more significant effect and must be avoided. For such material the invention has particular advantage where cutting is effected by means of cutting elements protruding upwardly into the mass of material through the region of roots and base portions of the plant material.

In some arrangements, the method may include applying to the plant material a component of force towards a medium in which the plant material is growing, by moving one set of elements with those elements inclined to the direction of movement of those elements, the elements having a trailing inclination relative to the direction of movement. Conveniently the said one set of elements comprise rods which extend into the plant material from above the plant material, and are inclined to the vertical by a trailing inclination relative to the direction of movement of the rods.

It is to be appreciated that where features of the invention are set out hereinbefore, or hereinafter, in connection with a method of separating plant material, these features are also provided in accordance with the invention in relation to apparatus for separating plant material, and vice versa. In particular, there is provided in accordance with the apparatus for separating plant material comprising a support structure for supporting a mass of plant material, two sets of spaced apart dividing elements mounted relative to the support structure to allow penetration of the elements into the mass of plant material, and displacement means for producing relative movement between the sets of elements in a direction transverse to the direction of penetration of the elements into the plant material, and in a manner such that elements of each set interpenetrate and pass between elements of the other set.

Preferably the apparatus is arranged so that in operation the two sets of dividing elements extend towards each other in opposed directions to an extent such as to overlap. Preferably the elements overlap throughout substantially the whole region in which they extend into the mass of plant material ^'in operation.

The apparatus may be a manually operated apparatus for use in improving the speed of a conventional micropropagation process by human operators, and the displacement means may comprise a guide structure enabling the appropriate movement of the elements to be effected manually. However the invention finds particular application in an automatic or semi-automatic micropropagation apparatus in which the apparatus includes first drive means for producing movement of one set of elements into the plant material in a first direction and movement of the other set of elements into the plant material in a second direction opposed to the first direction, and the displacement means comprises second drive means for producing the said relative movement between the sets of elements in a direction transverse to the movement in the first and second directions. Preferably the first drive means is arranged to produce movement of one set of elements into the plant material in a first direction, for example vertically downwardly from above the plant material, and to produce movement of the other set of elements into the plant material in a second direction opposed to the first direction, for example vertically upwardly from below the plant material. Preferably one set of elements are relatively blunt to a degree such as to effect separating substantially without a cutting action by those elements, and the other set of elements are relatively sharp to a degree such as to effect separating by an action including a cutting action by those elements. Preferably the support structure includes a base adapted to support a mass of plant material growing in a nutrient medium with shoots extending away from the base, the set of relatively sharp elements being mounted to extend from the base of the support structure into the mass of plant material through a region of base portions of the plant material, and the relatively blunt elements being mounted to extend towards the said base for supporting the plant material. However, in other arrangements, any of the combinations of sharp and blunt elements may be used e.g. both sets of elements may be sharp or both may be blunt.

In one preferred structure the said first set of elements comprises a plurality of rods, and the second set of elements comprises a plurality of blades, such as scalpel blades. Conveniently the said displacement means comprises means for effecting rotary movement of one set of elements relative to the other set. For example the said rods may extend downwardly from a first cylindrical plate, and the said blades may extend upwardly from a second cylindrical plate, the two cylindrical plates being arranged coaxially for rotation about a common axis, with the elements of the two sets interpenetrating and moving between each other during relative rotation of the two circular plates. In other arrangements the displacement means may comprise means for producing relative linear movement between the two sets of elements, for example a reciprocatory linear movement in which the elements of one set are drawn to and fro between the elements of the other set. It may also be convenient to provide means for effecting a reciprocatory rotary movement of one set of elements relative to the other. In accordance with another preferred feature of the invention, it may be arranged that one set of elements is mounted to be inclined relative to the direction of movement of that set of elements, the inclination of the elements being a trailing inclination relative to the direction of movement of the elements.

In some preferred arrangements, at least some of the dividing elements comprise rods having a cross-section such as to present a flat surface transverse to the direction of relative movement between the sets of elements. The rods may be of rectangular cross section, for example of square cross section.

It is particularly preferred that the dividing elements of one set comprise cutting elements, and the elements of one set are arranged in a staggered formation relative to the elements of the other set such that various of the cutting elements pass between various of the other elements at staggered time intervals. Conveniently, the cutting elements are positioned in a spiral configuration.

Embodiments of the invention will now be described with reference to the accompanying drawings in which:-

Figure 1 is a perspective view of the main components of a hand-held apparatus embodying invention for separating plant material during micropropagation, the components being shown in unassembled form;

Figure 1(a) is a diagrammatic plan view of a support structure of the apparatus of Figure 1;

Figure 2 shows a perspective view from the side of the apparatus of Figure 1, when assembled but in a non- operational position; Figure 3A shows the same apparatus as Figure 2 in cross-sectional view, but with a mass of plant material positioned at a work station of the apparatus ready for separation;

Figure 3B shows the apparatus of Figure 3A but with the apparatus moved to a later stage of operation and engaging the plant material;

Figure 4 shows the apparatus of the preceding Figures during operation when separating the plant material;

Figure 5 is a side view, partly in cross-section, of a motorised embodiment of the invention, generally similar to the hand held version shown in the previous figures, but adapted for semi-automatic operation;

Figure 6 is a front elevation of the apparatus of Figure 5;

Figure 7 is a front perspective view of the apparatus of Figures 5 and 6, with a mass of plant material positioned at a work station of the apparatus ready for separation;

Figure 8 is a perspective view of the main components of a modified embodiment of the invention, modified from the embodiment shown in Figure 1, the components being shown in unassembled form;

Figure 9 shows a perspective view from the side of the apparatus of Figure 8 when assembled but in a non- operational state; and

Figure 10 is a diagrammatic side view, partly in section of the embodiment of Figures 8 and 9, during operation when separating plant material.

Referring to Figure 1, apparatus for separating plant material comprises a support structure 11 comprising a shallow cylindrical metal dish 9 having a floor 8 and an upstanding cylindrical side wall 13. The support structure 11 also includes a base plate 12 positioned beneath, and spaced from, the floor 8. Five blades 16 rise vertically upwardly from the base plate 12 and may for example comprise scalpel blades secured to the base plate 12. The blades 16 are set on a spiral indicated by dotted line 17 in Figure la, and the blades are in register with five slots 7 in the floor 8 of the container 9.

The base plate 12 is fixedly secured to a knurled disc 15 set on a knurled boss 6. As will be described in more detail with reference to Figure 3A, the dish 9 is supported by a lower support shaft 14 (Figure 3A) which passes down into and through the knurled boss 6, and allows the container 9 to be moved between the upper position shown and a lower position in which the underside of the floor 8 rests on the upper side of the base plate 12, and the blades 16 protrude up through the slots 7.

In Figure 1 a second main component 2 of the apparatus is shown positioned next to the support structure 11. This component 2 comprises a circular support ring 18 mounted by spokes 21 on an upper support shaft 5. Also mounted on the upper support shaft 5 is a locating ring 32 mounted by further spokes 4. At the end of the upper support shaft 5 remote from the support ring 18, is a crossbar forming a top handle 3. The rings 18 and 32 are shaped to co-operate with a container for containing plantlets in a nutrient medium, such a container being shown by example at 26 in Figure 1. The purpose of the support ring 18 and spokes 21, is to carry a plurality of rods 20 which extend in parallel from the spokes 21, parallel to the upper shaft 5. Four and five rods 20 are provided respectively on alternate spokes 21, and in each case form a comb 19 provided on a radius of the support ring 18. Each rod 20 is of square cross-section. The number of rods in each comb, and the pitch and size, will be chosen according to the plant variety and state of growth. By way of example there may be provided between 2 and 6 rods on each radius, for a

300ml tub. The spacing between rods may be in the range 3 to 6mm, preferably 4 or 5mm, and the width of each rod transverse to its direction of movement may be in the range lmm to 3mm, preferably about 2mm.

Figure 2 shows how the two components 2 and 11 of the apparatus of Figure 1 can be assembled together ready for operation. The support structure 11 is positioned with the knurled boss 6 vertical and the upper components is positioned with the upper support shaft 5 vertical and coaxial with the knurled boss 6. The same arrangement is shown in Figure 3A, but with components shown partially in cross-section, and with plant material positioned ready for separating. The plant material comprises a mass of plantlets 24 which have been grown in a nutrient medium 25 consisting of a gel of agar containing plant nutrients, the plants and the agar being contained in a cylindrical plastics container 26. At a previous stage (not shown) the dish 26 is assembled on the support structure 11, by locating the container 26 inside the cylindrical wall 13 of the dish 9. At the stage shown in Figure 3A the base of the container 26 rests just above the tips of the blades 16.

Figure 3A shows in section further components of the support structure 11. The shaft 14 passes down through a cylindrical bore 28 in the knurled boss 6 and is located by upper and lower O-rings 29 and 30 in the bore 28. A cylindrical peg 31 extends downwardly from the floor 8 of the dish 9, and locates in a cylindrical hole 32A passing through the base plate 12 and the knurled disc 15. The hole 32A is parallel to and spaced from the shaft 14, and serves to prevent the dish 9 rotating relative to the knurled disc 15. The O-rings 30 provide means for restraining the shaft 14 in either an upper position as shown in Figure 3A, or a lower position as shown in Figure 3B. When in the position of Figure 3B, the shaft 14 protrudes below the boss 6, so that the shaft 14 can be returned to the upper position by pushing the protruding end of the shaft 14 upwardly relative to the boss 6.

There will now be described the operation of the manual apparatus described so far. The first step is to position the tub holder dish 9 correctly in the knurled boss 6, as shown in Figure 2, by pressing the lower end of the shaft 14 upwardly relative to the boss 6. The support structure 11 is then held in one hand, and with the other hand a tub 26 is placed in the tub holder dish 9 as shown in Figure 3A. Still holding the support structure 11 in one hand, the upper component 2 is then picked up in the other hand and the combs of rods 20 are inserted into the tub, using a slight oscillating motion to ease the passage of the rods of the combs between the plants 24. When the upper ring 32 is located within the mouth of the tub 26, the shaft 5 is pressed down firmly by pressure between the top handle 3 and the support structure 11, to drive the scalpel blades 16 upwardly through the base of the tub 26.

To divide the plant material, the top handle 3 is rotated clockwise through an amount of rotation dependent upon the plant variety and state of growth, for example in the range 1 to 3 complete revolutions, conveniently two complete revolutions, relative to the knurled disc 15, while applying a slight downward pressure. If the comb does not rotated freely, then the downward pressure is eased. Too much downward pressure can lead to distortion of the plastics tub by the bottoms of the rods rubbing on the floor of the tub. After the two turns, the combs 19 are withdrawn and any particles of plant material shaken free. Next the blades 16 are withdrawn from the tub by pressing the boss 6 firmly down on the bench thus pushing the base of the shaft 14 upwardly relative to the boss 6. The tub 26 is removed from the holder 9 and the separate plants are removed for replanting.

The top handle 3 and the knurled disc 15 constitute displacement means for producing relative movement between the set of blades 16 and the set of rods 20, by producing rotary movement between the two sets. The two manual gripping means 3 and 15 are also used to produce movement of the rods 20 and the knives 16 towards each other so that both the rods 20 and the blades 16 penetrate into the plant material. The two sets of elements extend towards each other in opposed directions to an extent such as to overlap throughout substantially the whole region in which they extend into the mass of plant material. The blades 16 protrude upwardly through the base of the container 26 into a region of roots and base portions of the plant material, and the rods 20 penetrate downwardly through the upper shoots of the plantlets 24 into the mass of plantlets in the region of the nutrient medium 25.

The rods 20 constitute a first set of dividing elements, and the blades 16 constitute a second set of dividing elements. The rods 20 and blades 16 are spaced apart, and positioned, in such a manner that rotation of the support ring 18 relative to the support structure 11, when in the lower position shown in Figure 4, produces relative movement between the rods 20 and blades 16 in a manner such that the blades and rods interpenetrate and pass between each other during the rotation.

The effect on the plant material of the rotation of the set of rods 20 relative to the blades 16, is that the plantlets are separated and individual stem portions of plantlets are divided, by a combination of effects including teasing apart of plantlets, prizing apart, and some cutting of plantlets at natural lines of division. It is observed that where stem portions are already separate, the knife blades pass between natural divisions without cutting, the plantlets often being pushed sideways by rods 19, and rotating about the rods. Where a plantlet has grown to such a size that two or more stem portions need to be cut, the plantlet will commonly bridge the space between two rods 20, and will be cut by a passing blade 16. Another useful effect of the blades 16 during rotation is that some excess root material is trimmed from the separated plantlets.

After the separating process, the main components are moved apart by raising of the support ring 18, and the container 26 is removed, lifting with it the separated plantlets. The final stage may be washing by water jet, which washes away excess trimmed roots, and also finally separates out the plantlets which have already been loosened, split, and/or cut. The components are then sterilised before use again.

It will be appreciated that a number of alternative forms of operation of the embodiment are envisaged. For example it may be convenient to remove the entire base of the container 26 before placing the container over the dish 9. The mass of plant material will hold together sufficiently with the nutrient medium 25, to allow the mass to be lowered over the blades 16. In another arrangement, the whole mass of plant material may be removed from the container 26 and may be placed in a support structure without the container 26 being present.

It is also to be appreciated that in its broadest aspect the invention encompasses the provision of more than two sets of spaced apart interpenetrating dividing elements, and in some examples a multiple movement of the sets of elements may take place with each set moving relative to the two or more other sets.

One difficulty that can occur is that the separated plantlets may be carried around the container by the rotation of the blades, and can sometimes be gathered together in one or another quadrant of the container. This difficulty may be avoided or reduced by having a reciprocatory motion of one set of elements relative to the other set of elements. In such a case, it is necessary for the blades to be sharpened on both sides.

Although the shape and configuration of the two sets of elements may be widely varied, there are a number of advantages in the form shown in Figures 1 to 4. There is advantage in having the knives 16 on a spiral configuration, in combination with the combs 19 along radii, because then the dividing elements of one set are arranged in a staggered formation relative to the elements of the other set, such that various of the cutting elements pass between various of the other elements at staggered time intervals. This ensure that the torque required for cutting is required evenly throughout the revolution of the combs. The arrangment also reduces bunching of the plant material and provides even separation in the container 26. It is also believed that the square section rods 20 are more advantageous than for example circular section rods, because the rods shown in Figure 1 present a flat leading surface transverse to the direction of movement of the rods. This is thought to present the plant material more advantageously to the knives for division or cutting.

There will now be described with reference to Figures 5, 6 and 7, a modification of the previously described manual apparatus, into a motorised semi-automatic apparatus embodying the invention for separating plant material. Where components of the embodiment of Figures 5 to 7 correspond to components in the previous figures, like reference numerals will be used.

The apparatus comprises a main frame 40 on which is mounted the support structure 11, and the upper component

2, constructed generally as shown in the preceding figures. The support structure 17 is mounted on a horizontal bracket 41 by a mounting which allows rotation of the support structure 11 about a horizontal axis by a control knob 42. In the normal operational position shown in Figure 5, the tub holder dish 9, and the base plate 12, are both mounted on a double acting pneumatic piston 43, which allows movement of the support structure 11 upwardly and downwardly relative to the bracket 41.

The second comb component 2 is mounted from above by a horizontally extending bracket 44. The shaft 5 of the upper component 2 extends through the mounting of the bracket 44 up to a knurled knob 45 at the very top of the apparatus. The shaft 5 is mounted in bearings 46 and 47 for rotary movement, and also is mounted to allow up and down movement of the shaft 5 relative to the bracket 44. The shaft 5 is biased upwardly by a spring 48 acting between the bracket 44 and the underside of the knob 45. The shaft 5 can be lowered by manual pressure on the knob 45, but is normally biased upwardly to a set vertical position. A pulley 49 mounted at the upper end of the shaft 5 is connected by a drive belt 50 to a further pulley 51, which is driven in turn by a motor 52 mounted on the main frame 40.

Thus, in summary, the apparatus is provided with first drive means indicated generally at 22, comprising the double acting piston 43 and associated components (not shown), for producing movement of the blades 16 into plant material in a first direction and movement of the rods 20 into plant material in a second direction opposed to the first direction. A second drive means indicated generally at 23, and including the motor 52 and drive belt 50 and pulley 49 and 51, is provided for producing relative movement between the blades 16 and the rods 20, by a rotary motion. Other components of the apparatus are provided for sterilising purposes, but these will be described hereinafter. There will firstly be described the detailed operation of the apparatus for plant material separating purposes.

Firstly a tub 26 of plants 24 is located in the tub holder dish 9 as shown in Figure 7. By appropriate operation of manual controls indicated by push-buttons 53, the double acting piston 43 is actuated to raise upwardly the base plate 12 together with the tub holder 9. The piston is arranged to move the dish 9 and the base plate 12 in a sequence such that the dish 9 is raised up to the combs 19 and the base plate 12 is then raised up relative to the dish 9 so that the blades 16 penetrate the bottom of the container and penetrate into the mass of plant material. The extent of movement of the pneumatic piston 43 is such that at the end of its travel the blades 16 fully penetrate into the container 26, with the base plate 12 resting against the underside of the dish 9, but a clearance is left between the bottoms of the rods 20, and the top of the floor 8 of the container 9. Next, by appropriate operation of the control knobs 53, the motor 52 drives the pulley 49, and rotates the combs 19, for example, through two complete turns of rotation, in the same manner as has been described with reference to the manual apparatus. The dish 9 and base plate 12 are then lowered, by the piston 43, including a stage in which the base plate 12 is lowered relative to the dish 9, and the blades 16 are withdrawn safely below the floor 8 of the dish 9. Any particles adhering to the combs 19 are removed firstly by striking the knurled knob 45 so as to lower the shaft 5 and release it to spring upwardly under the effect of the spring 48. This produces a dislodging action at the combs 19. If any stubborn particles remain adhering, these can be removed by forceps. Lastly, the tub 26 is removed from the holder 9, for replanting of the divided plant material.

The sequence of operation of the pneumatic cylinder 43 is that the piston 43 first rises, carrying the dish 9 and the base plate 12 upwardly together until the combs 19 enter into the mass of plant material. The base plate 12 then continues to rise, pushing the knives 16 up through the base of the container 26 until the top of the base plate 12 lodges on the underside of the tub holder 9.

During the reverse movement of the piston 43, the piston carries the tub holder 9 and base plate 12 downwardly together, until the bottom of the shaft 14 carrying the tub holder 9 strikes a lower casing of the double acting piston housing 56. This causes the knives 16 to be withdrawn safely below the level of the floor 8 of the tub holder 9.

Next there will be describe the method of sterilisation of components, after plant separation has taken place. As shown in Figures 6 and 7, a sterilising fluid container is provided at 57 mounted on an arm 58 extending from a rotary mounting 59 parallel to and spaced from the shaft 5. After separation has taken place and the container 26 has been removed, the arm 58 is swung around to bring the container of sterilising fluid 57 beneath the combs 19. The comb assembly 2 is lowered by applying manual pressure to the knob 45 against the spring 48 and the combs dip into the sterilising fluid. After this is completed the sterilising container 57 is again pivoted clear of the main axis. The lower assembly 11 is then rotated about a horizontal axis passing through the knob 42, until the support structure 11 is inverted and is pointing downwardly towards a second container 60 for sterilising fluid. By appropriate operation of the push buttons 53, the pneumatic piston 43 is actuated to propel the support structure 11 downwardly into the sterilising fluid in the container 60. After sterilisation, the assembly 11 is withdrawn upwardly, and is rotated again about the axis of the knob 42 to be brought back to the normal operating position.

Suitable sterilisation can be obtained by immersion in a ten percent bleach solution for three seconds, for example. Typically the plant tubs are conventional 300ml disposable plastic tubs. The double acting piston 43 may be operated for example by a 60/80psi lubricated air supply and a 24 volt DC supply may operate the control circuitry and the geared motor 52.

Referring to Figures 8, 9 and 10, there is shown a further embodiment of the invention. In Figures 8, 9 and 10, components corresponding to components in the previous Figures, are indicated by like reference numerals. As shown in Figures 8 and 9, the rods 20 are mounted on four radial arms 18A in place of the spokes 18, and the rods are positioned in rows of three rods on each arm. The rods 20 are inclined downwardly and rearwardly relative to the direction of rotation of the arms 18A. The blades 16 may be mounted and positioned in the same manner as shown in the preceding Figures, or in radial rows as shown. Other differences are that the rods 20 and the arms 18A are mounted on a shaft 14A which locates in a hole 19A in a base plate 12 on which the blades are mounted.

The object of inclining the rods 20 rearwardly is that in some cases the vertically located rods 20 of Figures 1 to 4, with the rods located parallel to the axis of rotation of the rods, produces an action of the blades 16 to displace the plants upwards. As shown in Figure 10, the arrangement of the rods 20 with a trailing angle of inclination imparts a downward component onto the plant 24 to ensure that the plant remains in the region of the blades 16 for dissection and separation. The horizontal component of the force applied by the rods 20 to the plants also helps to ensure that the plants interact positively with the blades 16. If it is desired to apply a reciprocatory rotary motion to the inclined rods 20 of

Figures 8, 9 and 10, then the rods may be mounted on the arms 18A to allow pivoting of the rods relative to the axis of the arm 18, between two stopped positions inclined on either side of a vertical through the arm 18A. Thus upon reversal of the direction of movement of a rod, the rod inclination changes from an inclination on one side of the vertical to the same inclination on the other side of the vertical, so as to provide the required trailing inclination relative to the new direction of rotation of the arms 18A.

An alternative to having the rods 20 inclined is to provide vertical rods 20 with a flat disc mounted immediately above the rods to prevent upward movement of the plantlets during relative movement between the rods and blades.

Claims

1. A method of separating plant material comprising: introducing into a mass of plant material two sets of spaced apart dividing elements, and producing relative movement between the sets of elements in a direction transverse to the general direction of growth of shoots of the plant material in such a manner that elements of each set interpenetrate and pass between elements of the other set.

2. A method according to claim 1 including presenting at a work station a mass of plantlets growing in a nutrient medium extending generally in a plane, introducing the dividing elements into the mass of plantlets in a direction or directions transverse to the plane of the medium, and producing the said relative movement between the sets of elements in the general plane of the medium.

3. A method according to claim 1 including introducing one set of elements into the plant material in a first direction, and introducing the other set of elements into the plant material in a second direction opposed to the first direction, the two sets of elements extending in the two opposed directions to an extent such as to overlap in the plant material.

4. A method according to claim 3 in which the elements overlap throughout substantially the whole region in which they extend into the mass of plant material.

5. A method according to claim 1 including engaging the plant material by one set of elements which are relatively blunt to effect separating without a cutting action by those elements, and engaging the plant material by the other set of elements which are relatively sharp to effect separating by an action including a cutting action by those elements .

6. A method according to claim 5 including introducing the set of blunt elements into the plant material through the region of shoots of the plant material, and introducing the set of sharp elements into the plant material through the region of base portions of the plant material.

7. A method according to claim 1 including producing the relative movement between the sets of elements by a rotary movement of one set of elements relative to the other set.

8. A method according to claim 1 including producing the relative movement between the sets of elements by a reciprocatory movement of one set of elements relative to the other.

9. A method according to claim 1 including applying to the plant material a component of force towards a medium in which the plant material is growing, by moving one set of elements with those elements inclined to the direction of movement of those elements, the elements having a trailing inclination relative to the direction of movement of the elements.

10. Apparatus for separating plant material comprising a support structure for supporting a mass of plant material, two sets of spaced apart dividing elements mounted relative to the support structure to allow penetration of the elements into the mass of plant material, and displacement means for producing relative movement between the sets of elements in a direction transverse to the direction of penetration of the elements into the plant material, and in a manner such that elements of each set interpenetrate and pass between elements of the other set.

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11. Apparatus according to claim 10 in which in operation the two sets of dividing elements extend towards each other in opposed directions to an extent such as to overlap.

5 12. Apparatus acordiήg to claim 11 in which the elements overlap throughout substantially the whole region in which they extend into the mass of plant material in operation.

13. Apparatus according to claim 12 in which the apparatus 10 includes first drive means for producing movement of one set of elements into the plant material in a first direction and movement of the other set of elements into the plant material in a second direction opposed to the first direction, and the displacement means comprises 15 second drive means for producing the said relative movement between the sets of elements in a direction transverse to the movement in the first and second directions.

14. Apparatus according to claim 10 in which one set of

20 elements are relatively blunt to a degree such as to effect separating substantially without a cutting action by those elements, and the other set of elements are relatively sharp to a degree such as to effect separating by an action including a cutting action by those elements.

25

15. Apparatus according to claim 14 in which the support structure includes a base adapted to support a mass of plant material growing in a nutrient medium with shoots extending away from the base, the set of relatively sharp

30 elements being mounted to extend from the base of the support structure into the mass of plant material through a region of base portions of the plant material, and the relatively blunt elements being mounted to extend towards the said base for supporting the plant material.

35

16. Apparatus according to claim 10 in which the said displacement means comprises means for effecting rotary movement of one set of elements relative to the other set.

17. Apparatus according to claim 10 in which the said displacement means comprises means for effecting reciprocatory movement of one set of elements relative to the other set.

18. Apparatus according to claim 10 in which one set of elements is mounted to be inclined relative to the direction of movement of that set of elements the inclination of the elements being a trailing inclination relative to the direction of movement of the elements.

19. Apparatus according to claim 10 in which at least some of the dividing elements comprise rods having a cross- section such as to present a flat surface transverse to the direction of relative movement between the sets of elements.

20. Apparatus according to claim 19 in which the rods are of rectangular cross section.

21. Apparatus according to claim 10 in which the dividing elements of one set comprise cutting elements, and the elements of one set are arranged in a staggered formation relative to the elements of the other set such that various of the cutting elements pass between various of the other elements at staggered time intervals.

22. Apparatus according to claim 21 in which the cutting elements are positioned in a spiral configuration.