What effect does hydrochloric acid and sodium hydroxide have on seed germination?

Question

If each solution is uncovered, will the seed germinate?

Answer 1

Both hydrochloric acid and/or sodium hydroxide are used in commercial production of "wet" seeded vegetables such as tomato seed production. Extraction. The tomato fruit is placed into a crusher that pulverizes the fruit and separates the gelatinous seed from the remaining fruit tissues by pressing them through screens. The extract containing the gelatinous seed material must still be separated from the remaining pulp. This is accomplished naturally by fermentation or with chemicals. When fermentation is used, the seeds remain in the extract until the gelatinous coating has been degraded by microorganisms; a process that can take up to three days under normal field conditions. The fermentation mixture is frequently stirred and inspected until this occurs. Excessive fermentation reduces seed quality. Chemical methods include the use of hydrochloric acid or sodium carbonate. Enough concentrated hydrochloric acid is added to the fermenting extract to make a 5% concentration. The acid rapidly degrades the gelatinous seed coating resulting in the production of a clean seed sample. Similar cautions concerning excessive digestion time on seed quality and concern about worker safety when using concentrated acids need to be emphasized with this technique. Sodium carbonate accomplishes the same task as hydrochloric acid without the potential danger to workers. However, it darkens the seed coats and makes the seeds less attractive as a commercial product. After seed extraction, the seeds are immediately washed to remove digested materials and any remaining chemicals. This is accomplished by placing the seeds and extraction in long, slightly angled water troughs that contain a series of riffles at specific intervals.

Answer 2

The first is a strong acid, the second a strong base; both will chemically degrade a seed coat. I would not recommend either, since they are extremely strong caustics and will both likely damage the germ inside. If you were to use them, you would need to expose the seed to the solution for no more than a few seconds, then flush with fresh water for several minutes after, at a minimum.

Not all seeds need to be scarified (seed coat breached) to germinate; many will split the coat themselves when they germinate. If not, typically sulfuric acid is used to chemically scarify. The procedure is different depending on the seed coat and seed. Alternatively, they can be physically scarified by roughing them up in a little tumbling machine that acts like a rock polisher.

Other seeds need to be "imbibed" or exposed to a period of cold before they will germinate. This is true for many biennials.