Turgor

Definition

The pressure exerted by fluid within a confined space against its surrounding walls, maintaining tension and structural rigidity. In arthropods, turgor refers primarily to hemolymph pressure within the body cavity (hemocoel), which assists in limb extension, molting, tracheal ventilation, and maintenance of body shape in soft-bodied or newly molted individuals. In botanical contexts relevant to entomology, turgor pressure in plant cells drives phloem sap flow and influences leaf toughness, thereby affecting herbivore feeding efficiency and host plant selection.

Etymology

From Latin turgor, from turgere 'to swell, be distended'

Example

A newly eclosed cicada relies on hemolymph turgor to expand its wings and harden its cuticle before the exoskeleton sclerotizes; without adequate turgor, the wings remain crumpled and the insect cannot fly.

Synonyms

• turgidity
• turgor pressure

Related Terms

• Hemolymph
• hemocoel
• molting
• Ecdysis
• Sclerotization
• Hydrostatic skeleton
• tracheal system
• phloem

Usage Notes

Distinguished from blood pressure in vertebrates by its role in hydrostatic skeletal function and its dramatic fluctuations during molting. In entomological literature, 'turgor' often appears without 'pressure' (e.g., 'hemolymph turgor'), whereas botanical literature favors 'turgor pressure.' The term applies broadly to any fluid-filled cavity; specialists may specify 'hemolymph turgor' or 'cell turgor' to avoid ambiguity.