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Bởi: Martin L. Price
Phát hành: 19-07-1997


Saving seed is a problem for farmers in hot, humid climates. It is even more of a problem for community, mission, or government seedbanks that must preserve seed for long time periods in remote locations without refrigeration. We believe the work of Dr. D. K. Pandey in India may be a breakthrough in reliable seed preservation in the rural tropics.

He published an article in Scientia Horticulturae 66 (1996, pp. 1-8) entitled “A suitable liquid preservative for enhancing longevity of orthodox seeds.” He calls this special seed-preserving liquid CALGLY, named after the two relatively common chemicals that are used to make it: calcium chloride (CaCl2) and glycerol. We were easily able to locate both substances for sale in Ft. Myers. CaCl2 sells for US$9.50 per gallon (sold as flakes), while glycerol costs US$45.45 per gallon.

Initial experiments had been done with pure glycerol, but seed absorbed the glycerol and was killed. Dr. Pandey discovered that adding CaCl2 to the glycerol prevented the liquid from being absorbed by seed.

CALGLY is made by heating glycerol to 156-160°C and then adding CaCl2, which dissolves. For every 75 grams of glycerol 25 g of CaCl2 is added.

Onion Seed Experiment. Onion seed is known for its tendency to lose viability during storage. Dr. Pandey dried fresh onion seed in the sun and found that this method reduced the moisture content (MC) of the seed to 10.5%. In his experiment, he used laboratory techniques to dry samples of onion seed to 10%, 8% and 2% MC.

It is well known that reducing the MC of seed even a few percentage points below what is possible to obtain by drying in the sun can improve seed storage life. Samples of seed at 10%, 8%, and 2% MC were stored in laminated aluminum foil seed packets (probably similar to the packaging in which ECHO’s seed is sent) while samples of 10% and 2% MC from the same lots were stored in vials to which CALGLY was added. The volume of CALGLY added to the vials was the same as the volume of the seed.

The packages and vials were stored for various lengths of time under natural temperatures which were typical of tropical conditions. Temperatures ranged between 15 and 45°C (59 to 113°F).

After 300 days, the viability of the seed stored in foil packages at 10% MC had dropped from an initial 96% to 0%. The seed lot stored at 8% MC had a remarkable 89% viability after 900 days. However, in 1100 days it had dropped to 0%. The seed that had been reduced in the laboratory to 2% MC still had a 90% viability after 2190 days (six years) when sealed in the laminated foil packet.

How did the seed stored in CALGLY fare? The seed with 10% MC did just as well as the non-CALGLY seed which had been reduced to 2% MC–both had 93% viability after 2190 days.

How about other kinds of seed? Seed of four other vegetables were evaluated: capsicum (Capsicum annum L. var. ‘Arka Gauraw’), chili (Capsicum annum L. var. 'Arka Lohit’), carrot (Daucus carota L. var. 'Nantes’) and pea (Pisum sativum L. var. 'HUP’). The four seedlots at the start of the experiment had MC readings of 8.4, 7.78, 8.3 and 9.0% repectively. The seedlots in foil packets became non-viable after 2, 4, 4, and 3 years. None of the seed immersed in CALGLY showed any significant loss of viability even after six years of ageing.

How does it work? Dr. Pandey believes the CALGLY solution works by “ultradrying” seed. He bases this on the fact that the performance in CALGLY was similar to that of seed in foil packets which had been ultradried using “time-consuming, cumbersome and expensive techniques.” However, at the end of the experiment he could not measure the precise MC of seed stored in CALGY because the viscous material coated the small seed and could not be removed sufficiently for the precise weighing that would be necessary. He has experiments underway to see if other seed can likewise be preserved in CALGLY. At ECHO we intend to do some tests of our own.

 

Is CALGLY dangerous? Both glycerol and CaCl2 are57-2 relatively non-toxic, are not mutagens, do not harm seed or plants, and do not pose corrosion, fire, health or environmental hazards. Glycerol is a constituent of antifreeze used in automobiles. Because of its sweet taste (about half the sweetness of cane sugar), you should not leave a large amount where an animal might be tempted to drink it. Calcium chloride is used to melt ice on sidewalks, to fireproof fabrics, in antifreeze mixtures, in fire extinguishers and in dust control on unpaved roads.

A note to scientists. I am impressed with this study. It is published in a refereed journal, treatments were replicated and statistical analyses were performed. In India, you can request a copy from Dr. D. K. Pandey, G. B. Plant Institute of Himalayan Environment & Development, Kosi-Katarmal, Almora 263 643, India. To save him postage, others can write us for a copy. However, unless you plan a research project, all essential information is included in the above article. Thanks to HortIdeas for calling our attention to Dr. Pandey’s work.


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