Which term describes a substance that tends to draw together or constrict soft organic tissue?

The term "astringent" specifically refers to a substance that causes contraction or tightening of body tissues, including soft organic tissue. In a medical or cosmetic context, astringents are often used to reduce bleeding from minor abrasions, to help remove excess oil from the skin, or to tighten the skin, therefore providing a feeling of firmness. The concept behind an astringent is its ability to precipitate proteins in tissues, leading to a tighter and firmer texture.

The other terms listed do not relate to this definition. "Garrulous" describes someone who is excessively talkative, especially on trivial matters, showing no relevance to the physical description of a substance. "Craven" refers to someone who is cowardly or lacking in courage, which has no connection to the notion of drawing or constricting tissue. "Florid" describes something that is excessively ornate or elaborate, often in reference to speech or writing, and again, does not pertain to the physical action of constriction. Thus, the term "astringent" is the only one that accurately captures the meaning needed in this context.