Density
Explanation
The method of separating seeds by immersion in water relies on the physical property of density. This technique is commonly used in agriculture to distinguish between healthy, viable seeds and those that are damaged, hollow, or non-viable.
Analysis of the Principle
- Viable Seeds: Healthy seeds are structurally intact and packed with reserve food materials (such as starch and proteins) within the endosperm or cotyledons. This internal mass gives them a density greater than that of water, causing them to sink.
- Damaged Seeds: Seeds that are undeveloped, eaten by insects, or structurally compromised often contain air pockets or lack internal substance. This results in a density lower than that of water, causing them to float.
Consequently, the separation is driven by the difference in density, rather than solubility (seeds do not dissolve), surface texture, or particle size.
Key Takeaway: The water immersion test for seed viability functions on the principle of density; heavier, intact seeds sink, while lighter, hollow, or damaged seeds float.