What chemical tests seed viability?
Written by
Paul Reynolds
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.Tetrazolium chloride (TTC) is the principal chemical available for scientific testing of seed vitality. This colorless salt solution combines with the living tissues of the seeds to form a red formazan dye, a product of cellular respiration. Cells and tissues that are deficient in metabolic activity do not exhibit the color change. Dead cells and plants do not show any color.
Proper seed preparation is essential in the staining procedure. Cut half the seeds lengthwise to expose their embryonic tissue and soak the seeds in a 0.1-1% TTC solution at 86-95°F (30-35°C) until living cells stain a deep red. The staining will take place within a period of six to twenty-four hours. I plan to place them in petri dishes on a heating mat to conduct the test in a constant-temperature environment.
When working with tetrazolium, it is essential to take safety measures. Wear nitrile gloves and eye protection, as TTC can irritate the skin. Work in well-ventilated areas to avoid exposure to fumes. Store solutions in dark glass bottles, as light can degrade the chemical. Adequate handling will produce results accurately.
Solution Preparation
- Concentration: 0.5-1% TTC in distilled water
- Storage: Dark glass bottles at 40°F (4°C)
- Shelf life: 6 months when refrigerated
- Safety: pH-neutral solution reduces corrosion risk
Staining Process
- Temperature: 86-95°F (30-35°C) optimal
- Duration: 2-24 hours depending on seed size
- Observation: Use 10x magnification for small seeds
- Control: Include known viable/non-viable seeds
Result Interpretation
- Full red: 90-100% viability
- Partial red: 40-80% viability (depends on staining location)
- Colorless: 0% viability
- False positives: Rare but check for damaged tissue
Understanding seed structure is necessary for interpreting the results. In dicots, such as beans, the part of the seed best suited for study is the embryonic axis, while in monocots, such as corn, the scutellum should be studied. Partial staining indicates lowered viability. This technique applies to dormant seeds that do not germinate normally.
Despite its excellent accuracy, the tetrazolium test has some limitations. It cannot predict the speed of germination as accurately as germination tests. In some seeds, such as onions, the natural pigments prevent the test from being effective. The combination of germination testing makes an ideal approach to determine the viability of seeds before important plantings.
Read the full article: Seed Viability Test Guide: Ensure Your Seeds Grow
