GB2168322A - Water transpiration bag - Google Patents

Abstract

A water transpiration bag (10) within which foliage is located to enable water of transpiration to be collected, has an open end (11) through which the foliage may be inserted in the bag (10) provided with a draw string (12) to close the bag (10) about the foliage. The bag (10) further is provided with a tap (13, 15) to enable drainage of water from within the bag (10). <IMAGE>

Description

SPECIFICATION Water transpiration bag The present invention relates to apparatus for and methods of obtaining survival water from transpiration of plant foliage.

Theoretically water of transpiration should be safe for human consumption, because plant toxins are non-volatile and therefore will not be transpired along with water vapour.

It is the object of the present invention to provide a device to aid in the collection of water of transpiration.

There is disclosed herein a water transpiration bag within which foliage is locatable to enable the collection of water of transpiration therefrom, said bag being of robust construction to inhibit tearing and piercing by the foliage, and having an open end enabling the foliage to pass therethrough to be located within the bag, means to substantially close said open end so as to substantially sealingly locate the foliage within the bag, and tap means remote from said open end to enable the water of transpiration to be drained from the bag.

A preferred form of the present invention will now be described by way of example with reference to the accompanying drawing wherein: Figure 1 is a schematic side elevation of a bag to aid in the collection of water of transpiration from plant foliage; and Figure 2 is a schematic illustration of the bag of Figure 1 in use.

In the attached illustrations there is schematically depicted a bag 10 having a generally tubular configuration so as to provide an open end 11. The end 11 is provided with a drawstring 12 to facilitate closing of the end 11. The other end of the bag 10 is provided with a tube 13 which communicates with the interior of the bag 10 so as to enable the draining of water from within the bag 10. The other end of the bag 10 is sealed and provided with a tie-down eyelet 14. Preferably the tubes 13 would be formed of flexible plastics material to enable the selective closing thereof by means of a closing tab 15 having a major aperture 16 through which the tube 13 would pass when water is being drained from the bag 10. When the tube 13 is to be closed the tube is compressed so as to be located within the narrower opening 17.

The final technique for obtaining survival water from arid zone vegetation was examined at length.

Experiments showed that bags used should be clear, transparent and robust. Bag shape should be oblong with an optimum size of 1.8 x 1.0 metres.

Use of the bag is facilitated by a tie-down eyelet and drain plug or clamped drinking tube placed in one corner.

In selection of the host tree it is worthwhile to consider tree size and location, also the density, verdancy and size of the leaves, tree root system and limb thickness. Large broad-leafed trees with thick verdant heads of foliage are obviously better water producers than small sparse trees and shrubs with spikey foliage. Also trees that border watercourses may be tapping free ground water sources and therefore are less reliant on soil moisture than are shallow rooted trees. Irrespective of the tree used, branches selected should be the thickest availabe. Additionally, to maximise solar radiation (insolation), branches selected should face north. For many of the above reasons, Eucalyptus species, particularly riparian eucalyptus, are the most prolific water transpirers amongst Australian arid zone plants.

Tree selection and climate directly affect the quantity of water produced. Rainfall seasons, air temperature and insolation all affect the rate of water transpired by plants. Rainfall season probably has the greatest influence, and in periods of drought, yields are dramatically reduced (100-300 ml), whereas in wet seasons yields of over 2 litres per bag per day are possible. Generally larger eucalypts are capable of an average of 1 litre irrespective of the season, while smaller trees produce average yields of 4 to 6 litres in normal seasons.

Australian xerophytic plants do not transpire at night and therefore bags are most effectively used between 0700 and 1700 during the day. They should be left static for this total period rather than being moved from branch to branch. This is because leaf stomata do not close once the bag environment reaches saturation point and maximum temperature as one would expect; but the high relative temperature appears to cause loss of stomatal control and free flow of moisture ensues. First day collection of water is normally higher than that of subsequent days. For this reason and the greater chance of toxin leaching in later yeilds, collection of water beyond one day from the same branch is not advised.

Repeated trialling of this technique and subsequent testing of water for toxin presence disclosed the most efficient mode of operation for the method. The following seven basic steps were identified: a. Step 1: Select best tree Select a well foliated tree with spreading low branches, preferably broad-leafed, riparian and of the Eucalyptus species. Avoid known toxin carriers, aromatic plants, or plants with latex (milky sap).

b. Step 2: Choose best branch Choose the thickest low hanging branch with a good head of foliage that faces north.

c. Step 3: Prepare branch Remove any branchlets or leaves from the branch that will not fit into the bag, and bind up the remaining foliage with cord to facilitate bag fitting. Also remove any overhang that may cast shadow on the bag.

d. Step 4: Fit bag Carefully slide the bag over the bound foliage with the anchor point and water sump to the bottom. Ensure the sump is free of leaves. Secure the bag opening tightly to the branch with cord. Patch up any holes or tears with tape, because it is necessary that the bag is air tight for best results.

e. Step 5: Anchor branch Bend the branch down until the bag's water sump is below the level where the bag is secured to the tree. Anchor the branch in this position with cord. Note: The bag tie-down eyelet is convenient for this purpose provided the force required to bend the bag is not excessive. Alternatively, fix the tie-down cord to the branch itself, or select another branch.

f. Step 6: Check bag Check the bag at intervals during the day to ensure it has not come undone, been tampered with by fauna, been shaded from sunlight or has foliage lying in the sump.

g. Step 7: Drain bag Drain the water through the plug at the end of the day and remove the bag. If the tree species used is unknown, conduct a 'taste test' on the water before ingestion.

The water of transpiration method is not totally safe for general use with Australian arid zone plants. Most trees that were tested yielded toxinfree water, but a few plants produced water that reacted positively to alkaloids with either first and/ or second day yields. Of these,some were known alkaloid carriers while one tree was not. Surprisingly, specific tests with notorious alkaloid carriers were not always positive. This lack of consistency is believed to be due to the different stages of cellular break-down of the foliage that occurred in each separate test.

Eucalypts proved invaluable trees with this method. Yields from these trees were toxin-free on every occasion, which supports the literature that arid zone eucalypts are free of known plant toxins.

However survivors should not be restructed solely to use of eucalypts. Other tree species can be used, providing the seven basic steps listed above are followed.

Finally the method was shown to be economic for survivors with little or no loss of valuable body fluid with its operation. Because specialised equipment is required and some expertise needed, the technique is graded as 3 for degree of difficulty.

The bag 10 described above may be manufactured from the following materials. Low density polyethylene film (LDPE) of 100 microns would be suitable except that it would possibly be perforated with very rough handling. This material is obtainable through ICI as 'Vis Queen LDPE' (R.T.M.). Superior perforation resistance could be achieved by using a polyester base film laminated with either LDPE or ethylene vinyl acetate (EVA). This would be obtainable through ICI.

The tube 13 could be made from LDPE or a clear plasticized polyvinyl chloride (PVC). A blend of these two materials is preferred for better flexibility and longer life.

Claims (6)

1. A water transpiration bag (10) within which foliage is locatable to enable the collection of water of transpiration therefrom, said bag (10) being of robust construction to inhibit tearing and piercing by the foliage, and having an open end (11) enabling the foliage to pass therethrough to be located within the bag (10), means (12) to substantially close said open end (11) so as to substantially sealingly locate the foliage within the bag (10), and tap means (13, 15) remote from said open end (11) to enable the water of transpiration to be drained from the bag (10).

2. The bag (10) of claim 1 wherein said means to close said open end (11) is a drawstring (12).

3. The bag (10) of claim 1 or 2 wherein said tap means (13, 15) includes a tube (13) which may be selectively closed to retain the water within the bag (10).

4. The bag (10) of claim 1 wherein said bag (10) is formed of low density polyethylene film of about 100 microns thick.

5. The bag (10) of claim 1 wherein said bag (10) is formed of polyester film laminated polyethylene film or ethylenevinyl acetate.

6. A water transpiration bag substantially as hereinbefore described with reference to the accompanying drawings.