Abstract: The hydroponics attachment capable of steady growing of even taproot-type plant and easy plant relocation includes: the cap member with the opening at its top, which is detachably screwed, via the threaded portion, on the mouth of the drink bottle; the bottomed cylinder-shaped case body fitted in the opening; and the water-holding element placed in the case body for absorbing water in the drink bottle, so that hydroponics can be done with absorbed water. The single-piece water-holding element is made of a plurality of aligned filaments. The case body has, at its bottom, the insertion hole for guiding the plant's root growing downward through the water-holding element to go under the case body. The opening dimension of the insertion hole is smaller than the outer dimension of the water-holding element.

Abstract: A reactive liquid is coated on an ion exchange resin precursor membrane for the hydrolysis treatment. Preferably, a reactive liquid having a viscosity of not lower than 50 mPa·s or a small surface tension is used. Said precursor membrane is also subjected to the hydrolysis treatment under constraint, while the precursor membrane is maintained in a widened or a stretched state.