Is sprouting good or a bad? The answer depends on the application. For most of us, sprouted wheat is on our mind – which is bad. But we can learn something from the malting industry where sprout is a good thing. Malt is a result of sprouted barley. Barley is exposed to all the conditions which would be ideal for seed germination. Sprouting barley converts the starches found in the endosperm to sugars. Those sugars are used for a seedling to grow, or they can be used to produce the sweet taste of malt. The sugars in malt can then be used in beer to produce alcohol.
Sprouting is not a one size fits all situation. In the case of wheat, it is a result of variety, environment, and duration. Sprouting is in essence the germination of seed. Although there are ideal conditions for seed germination, there are also conditions in which germination, or enzymatic activity, can occur. This past growing season is a testimony.
So how do we test this? Michigan Crop Improvement has 3 tests which all tell us something unique about the seed: standard germination, TZ, and Accelerated Aging.
Standard Germination – For sprouted seed this test can be a bit misleading, based on the timing of seed testing. It is intended to determine what seed will germinate and grow. Sprouted seed has initiated the germination process, and when tested shortly after harvest, will continue to grow and produce a seedling. However, this may not be the same as when seed is planted in the Fall. Because of the early enzymatic activity, sprouted seeds will deteriorate and germination rates will follow.
Tetrazolium Test – In the TZ test, seed is imbibed, and then stained with tetrazolium solution. The staining is very good at showing seed embryo respiration. Depending on the level of sprouting, an embryo may show light color due to decreasing enzymatic activity or dead portions of the embryo, such as the radicle. The TZ test does not pick up seed which is primed and ready to grow which has not started to deteriorate. A typical grain TZ result will list a germination rate with a category of weak seeds. Weak seeds found in a TZ test will continue to deteriorate and may not be viable at planting in the Fall.
Accelerated Aging (AA) Test – The AA test pre-conditions seed in a high temperature and high humidity environment prior to placing it in the ideal conditions for seed germination. This pre-conditioning deteriorates weak seed while strong seed is able to survive. In sprouted seed lots there can be enzymatic activity with or without visible sprouting. Seeds with high enzymatic activity will also deteriorate in the AA test.
Each test tells us a unique component of the seed lot and each seed lot is unique. The only way to truly know the quality of the seed is to test the seed lot. One of the first samples tested had the following results:
TZ Test 92%
Weak (TZ) 4%
AA Test 80%
If this seed were planted today 95% of the seeds would grow. The TZ shows us that some deterioration is occurring from sprouting down to 88%. The AA test shows us that additional enzymatic activity is occurring from sprouting down to 80%.
There are certain components of life which are yes/no and there are certain components which are more gradient. There is a component of seed germination of will the seed grow. There is also a component of how well it will grow.