Front Range Seed Analysts
1992 Seed Forum Volume 6 Number 2
SHOULD GIBBERELLIC ACID ABE USED IN ROUTINE SEED TESTING?
NO!
Arnold L. Larsen
The application of gibberellic acid (GA) stimulates seed germination in many species. This has been known for many years. GA has been used commercially on plants with various positive benefits, but has not. been commercially applied to seeds. I suspect the cost of large scale application of GA and unproven benefits in the field has something to do with the lack of GA application to seeds. GA is used in laboratories where there is an apparent resistance to quick germination caused by dormancy mechanisms. GA either eliminates or bypasses these mechanisms and with adequate moisture, light and temperature, germination will occur. In most seeds of domesticated species, man has bred out resistance to germination, yet there are still some unusual species where latent dormancy mechanisms surface. In these special cases, the seed analyst cannot demonstrate maximum viability in terms of germination because viable ungerminated seeds remain after the standard germination test time has lapsed. Then the seed analyst yields to the temptation of testing the seeds with an application of GA so that all viable seeds germinate.
This presents a problem. The planter now has a report that states all viable seeds in the atypical seed lot will germinate as seeds of a typical lot. However the dormancy may cause delayed or irregular emergence in the field possibly resulting in economic losses.
Relative dormancy is an important quality factor that should be determined in all seed lots. If all viable seeds germinate within the standard time. prescribed for a species, then total viability and germination percentages are reported to be the same. often, some of the seeds do not germinate within the standard time and any found viable are designated as "dormant". The viability of the ungerminated seeds is determined by some other procedure such as the tetrazolium test. AOSA Rules specifies that viability shall be reported as percent germinated seed, percent dormant (or hard) seed and the sum of the two percentages.
The use of GA would negate the assessment of dormancy in seed testing. The knowledge of dormancy in seed lots is valuable information to the seedsman. Having this knowledge the owner can make marketing, storing, and planting adjustments to accommodate the dormant condition. Many rangeland and revegetation species are found to have deep dormancy which evolved as vital survival mechanisms. The presence of dormancy is an assurance to the owner that the seed has the ability to endure hostile environmental conditions. Not determining relative seed dormancy in these species would grossly misrepresent their quality.
When seed are commercially treated with GA, we will then test the seeds with GA as they are submitted. We still should not apply GA artificially in routine quality testing. Give seedsmen the maximum information regarding the quality of their seed in the condition that the seed will be presented to the customer.