Plant husbandry – Water culture – apparatus or method – Cultivating chamber
Reexamination Certificate
2000-11-06
2002-07-23
Jordan, Charles T. (Department: 3644)
Plant husbandry
Water culture, apparatus or method
Cultivating chamber
Reexamination Certificate
active
06421956
ABSTRACT:
The present invention in the first place relates to a method for treating seed with a fluid, in particular water, involving the use of a fluid-containing gas.
In intensive agriculture it is important to supply high-quality seeds that germinate well, rapidly and uniformly. To improve the seed quality in these respects, seed which in the dry state shows hardly any metabolic activity and therefore is resting, is activated (“priming”) by the seed being treated, for example, with water. As a result, the resting stage is interrupted and germination is stimulated. The treatment causes the seed to take up water (imbibition), as a result of which germination processes, not observable from the outside, commence in the germ.
The treatment with water does however entail a major risk that the seeds will actually germinate (i.e. that the root tip penetrates the pericarp). What should be aimed for, however, is to interrupt the water treatment just prior to the moment of germination, so that germination will not occur. After the treatment the seeds can be sown or can be dried (dehydrated). What has been found is that the pretreated, dehydrated seeds exhibit a high degree of germination synchronicity when they are sown and, moreover, keep well in this dry state.
The treatment with water does, however, have various problems which even today have not yet been resolved.
A method is known in the prior art which involves seeds being treated with steam in a rotating drum (U.S. Pat. No. 5,119,589). The steam condenses on the inside of the drum, with which the seeds keep coming into contact owing to the rotary movement of the drum. The seeds absorb this moisture and are removed from the wall by means of a scraper. This method has the drawback that the seeds are subjected to considerable physical stress, entailing a high risk that the seed will be damaged and will not germinate.
It is an object of the present invention to overcome the abovementioned drawbacks, the invention to this end being characterized in that seed is brought into contact with a gas having a controlled fluid content and the seed is kept in contact with the gas over a defined period whilst direct contact between the seed and the fluid in liquid form is substantially precluded.
The method of the present invention provides an excellent pretreatment of seed, without the latter coming into contact with fluid in liquid form and without the seeds having to be exposed to mechanical stress, as the fluid in question can be directly taken up by the seeds from the gas phase. It has also been found that with the aid of the method according to the present invention very precise pretreatment of the seeds can be ensured. Moreover, it has been found that a treatment according to the present invention leads to high-quality pretreated seed.
In this context reference is made to Allen et al., (Hort. Science, Volume 27 (4), pp. 364-366), who describe a method for pretreating seed with water by incubating the seed in an aqueous polyethylene glycol solution having a defined osmotic potential. This method, also referred to as “osmopriming”, is generally known, but is expensive, given the large quantities of polyethylene glycol which are needed, and requires complicated treatment steps, during which large quantities of polluting polyethylene glycol have to be discharged in some way. Moreover, the uptake of oxygen by the seed is hindered by the viscous polyethylene glycol. Alternatively, the seeds can be subjected to osmotic treatment on a solid support, as described in U.S. Pat. No. 4,912,874. With this method, large quantities of polluting wastes are formed and there is a risk of the seed being damaged.
Preferably, the gas phase is substantially stationary and the fluid transport through the gas phase towards the seed takes place substantially via diffusion. With a stationary gas phase it has been found that the seed takes up the fluid very uniformly and slowly, diffusion processes playing a crucial part. The slower water uptake has advantages over the more rapid water uptake taking place in the case of osmopriming and water/steam treatment.
In particular, the fluid comprises water, in an amount of 99% or more. Whilst the method, in principle, is suitable for the pretreatment of the seeds with any liquid, the pretreatment generally takes place with water. This water can also contain supplementary substances such as minerals, hormones, pesticides and/or stimulants. Such substances can, however, also be added to the gas phase, if desired. For decontamination purposes use can be made, for example, of water containing chlorine bleach, for example in a concentration of 0.4 w/w%.
It should be clear that where the application refers to “fluid content of the gas phase” this can be read, in the case of water as the fluid used, as “relative humidity”. If the gas phase is formed by air, the abovementioned term is comparable with “relative air humidity”.
The optimum relative humidity for priming depends on the seed to be primed. It has been found that very good priming is achieved if the relative air humidity is 98% or more. In a preferred embodiment of the present invention, the relative humidity is 98% or more, more preferably 99% or more. Optimum priming is generally achieved if the humidity is maintained just below the saturation point in the gas, without saturation of the gas with the fluid occurring. Thus the moisture content is as high as possible, as a result of which priming of the seed can take place very rapidly and effectively. A fluid-saturated gas is undesirable, as there is then the risk that the fluid will condense on the seed, which can be deleterious as already described above.
Advantageously, the temperature of the gas is between 2 and 40° C., preferably between 8 and 30° C. In the latter temperature range good priming takes place, although higher or lower temperatures are possible. At higher temperatures, however, problems may occur, since not all types of seed may be resistant to such high temperatures.
Below 5° C., moisture will indeed penetrate the seeds, but the resting stage will not or virtually not be disturbed, and priming generally takes place to an insufficient degree.
Preferably, the temperature of the seed at the beginning of the treatment is between 8 and 35° C., as this temperature range corresponds to the temperatures to which the seeds or plants are generally exposed in nature.
Preferably, the temperature of the seed at the beginning of the treatment is equal to or higher than that of the gas. This prevents, at the beginning of the treatment, liquid or water from condensing on the outside of the seeds, the seeds thereby coming into contact with the liquid, with all the deleterious consequences already described above. Condensation on the seeds also results in a lower germination synchronicity being achieved.
Advantageously, the seed is treated over a period of 1-14 days. A longer treatment may lead to unwanted germination, whilst a shorter treatment may lead to inadequate synchronicity, as a result of a large number of seeds still being in the germination resting stage because they have not taken up enough water. The optimum duration of the treatment may differ between types of seed.
It has been found, surprisingly, that if the seed prior to the abovementioned fluid treatment is incubated in an environment which is saturated with said fluid, it is possible for optimal and well-synchronized accelerated priming to be achieved. The fact is that it has been found that the seeds which, in the dry state, have an osmotic pressure of from −400 to −100 MPa, first take up a considerable amount of water before the seeds become physiologically active and priming proper starts. This physiologically active phase sets in when the seed has taken up so much water that its osmotic pressure is greater than −10 MPa. “Greater than −8 MPa” refers to an osmotic pressure whose value is above −8 MPa. In principle this therefore means that a higher value amounts to a lower water uptake capacity. The said phase usually commences
Boukens Marcel Adrianus Nicolaas
de Boer Jan
van Dok Ijsbrand
Ijsbrand Van Dok
Jordan Charles T.
Lofdahl Jordan
Stroock & Stroock & Lavan LLP
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