Plant husbandry – Water culture – apparatus or method – Nutrient recirculation system
Reexamination Certificate
2001-08-13
2003-09-09
Jordan, Charles T. (Department: 3644)
Plant husbandry
Water culture, apparatus or method
Nutrient recirculation system
C047S063000, C047S064000, C071S036000
Reexamination Certificate
active
06615539
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority of International application No. PCT/JP99/06187, filed Nov. 5, 1999, which in turn claims priority to Japanese patent Application No. 10/316440, filed on Nov. 6, 1998, Japanese patent Application No. 11/20394, filed on Jan. 28, 1999, Japanese patent Application No. 11/50305, filed on Feb. 26, 1999, and Japanese patent Application No. 11/290552, filed on Oct. 13, 1999.
TECHNICAL FIELD
The present invention relates to a water-retaining support (or carrier) for plants and a plant body-growing water-retaining material which can support or hold a plant at the time of the growth of the plant and can also function as a source for supplying water to the plant. More specifically, the present invention relates to a water-retaining support for plant and plant body-growing water-retaining material which can supply water to a plant without inhibiting the growth of the plant, when the support is used as a water-retaining support for fluid seeding (or seeding using a fluid), farm cultivation, field (or bare ground) cultivation, virescence (or greening) engineering, etc.
BACKGROUND ART
Polycarboxylic acid-type highly water-absorbing resins, especially polyacrylic acid-type polymers, which have been used in a large quantity for diapers, menstrual goods, etc., are also used in the field of agriculture due to their inexpensiveness and excellent water-retaining ability.
For example, hydrogels of the polyacrylic acid-type polymers have been used as a support for fluid seeding; or a water-retaining support for virescence engineering, water-saving cultivation, or cultivation on sandy soil, by utilizing their water-retaining ability.
However, it has been recognized that the conventional polyacrylic acid-type hydrogels affect the growth of a plant, and particularly, they cause a marked inhibition of the root origination and root elongation when the hydrogels are used in an amount exceeding their appropriate amount (Kazuo Kawashima, et al., “Influences on The Early Growth of Vegetables by a Super Absorbent With Cross-linked Forms of Polyacrylate,” Sand Dune Research Institute, 31(1), 1-8, 1984).
Particularly, when the conventional polyacrylic acid-type hydrogel is used as a support for tissue culture, a support for fluid seeding, and a support for virescence engineering, a plantlet, seed, etc., of a plant is caused to directly contact the high-concentration polyacrylic acid-type hydrogel, and therefore its root origination and root elongation are markedly inhibited, whereby the use of the polyacrylic acid-type hydrogel is severely restricted.
It has also been recognized that, in a case where the conventional polyacrylic acid-type hydrogen is used as a water-retaining support for farm or field cultivation, the elongation of the root is inhibited when the concentration of the polymer in the vicinity of the root is increased so as to enhance the effect of the water-retaining support.
As an example of the phenomenon such that the above-mentioned hydrogel comprising a polyacrylic acid-type resin markedly inhibits the growth of a plant, there has been reported an experiment wherein distilled water was absorbed into a crosslinked sodium polyacrylate so as to form a hydrogel, and the thus obtained hydrogel was caused to contact seeds of cucumbers and kidney beans for respective periods of time (3, 6, 9, 12, 24 and 48 hours), and then the states of the germination and root origination of the seeds were observed (Kazuo Kawashima, et al., “Influences on The Early Growth of Vegetables by a Super Absorbent With Cross-linked Forms of Polyacrylate,” Sand Dune Research Institute, 31(1), 1-8, 1984).
As a result of such experiments, it has been reported that the growth of roots was markedly suppressed in the case of cucumber seeds, when they are caused to contact the hydrogel for 36 to 48 hours, and that the inhibition of root growth was also observed in the case of kidney beans. Further, it has been reported that the &agr;-naphthylamine-oxidizing ability of the root was markedly reduced when the root is caused to contact the above-mentioned hydrogel for 5 hours or more. In this report, such growth inhibition and functional hindrance are presumably attributable to a fact that the plant cannot effectively use the water contained in the hydrogel.
On the other hand, it has been reported that, when rice seeds were sown on a hydrogel which had been prepared by causing crosslinked sodium polyacrylate to absorb water, and then the process of the root origination was observed, serious hindrance in the root origination was recognized (Yorio Sugimura, et al., “Utilization of High Water-Absorptive Polymers as Greening Engineering Material,” Techniques of Virescence Engineering, 9(2), 11-15, 1983). In this report, however, no hindrance in the root origination was observed when the hydrogel was dialyzed with tap water, but the recovery of the root growth was not observed even when the hydrogel was dialyzed with distilled water. With respect to this phenomenon, in this report, it is presumed that, when the hydrogel is washed or dialyzed with a weak electrolytic solution such as tap water, the water-absorbing force toward the hydrogel was weakened, and the migration of water from the gel to the root hair is facilitated, to thereby solve the hindrance in the root origination.
There has also been reported an example wherein the degree of the elongation of soybean root was markedly inhibited in a soil which had been mixed with a crosslinked sodium polyacrylate hydrogel, as compared with that in the case of a polyvinyl alcohol-type hydrogel (Tomoko Nakanishi, Bioscience & Industry, 52(8), 623-624, 1994). In this reference, this phenomenon is presumably attributable to a fact that the water in the sodium polyacrylate hydrogel is less liable to be utilized by a plant.
As described above, it has heretofore been considered that the inhibition of the growth of a plant in a hydrogel comprising an alkali metal salt of crosslinked polyacrylic acid is attributable to the fact that the water in the hydrogel is not effectively utilized by the plant.
An object of the present invention is to provide a water-retaining support for plants which has solved the above-mentioned problems of the hydrogel water-retaining
Another object of the present invention is to provide a water-retaining support for plants which has a water-retaining ability comparable to that of the conventional polyacrylic acid-type hydrogel, and does not substantially cause an inhibition of root origination or of root elongation.
A further object of the present invention is to provide a plant body-growing water-retaining material which has a good water-retaining ability and does not substantially cause inhibition of root origination or of germination of a plant.
As a result of earnest study, the present inventors have found that the effect of a hydrogel is so strong that the inhibition of the root elongation cannot be simply attributable to the effectiveness in the utilization of water in the hydrogel.
As a result of further study based on the above discovery, the present inventors have also found not only that the calcium ion-adsorbing ability in the hydrogel has an important effect on the inhibition of root origination or the inhibition of root elongation of a plant which is in contact with the hydrogel; but also that, in combination with the above-mentioned calcium ion-adsorbing ability, chlorine ions present in the hydrogel also have an important effect on the inhibition of root origination or on the inhibition of root elongation of a plant which is in contact with the hydrogel.
DISCLOSURE OF INVENTION
The present invention relates to a water-retaining support for plants comprising a hydrogel-forming polymer (A) having a calcium ion absorption of 0-100 mg per 1 g of the dry weight thereof, having a chlorine ion content of 0.07-7 mmol per 1 g of the dry weight thereof, and having a water absorption magnification in ion-exchange water at 25° C. of 1.0×10
1
to 1.0×10
3
; and to a plant body-growing wa
Furukawa Koji
Kasuya Kazuhiro
Mori Yuichi
Obonai Yasuhiro
Yoshioka Hiroshi
Christie Parker & Hale LLP
Hayes Bret
Jordan Charles T.
M&M Laboratory Co., Ltd.
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