1. The tendency of certain plant organs, as leaves, to assume special "sleeping" positions or make curl up under the influence of darkness

Derived forms: nyctitropisms

• hydrotropism
• hydrous
• hydroxide
• hydroxide ion
• hydroxy
• hydroxy acid
• hydroxyacetic acid
• hydroxybenzene
• hydroxybenzoic acid
• hydroxybutyric acid
• hydroxychloroquine
• hydroxyl
• hydroxyl group
• hydroxyl ion
• hydroxyl radical
• hydroxylamine
• hydroxymethyl
• hydroxyproline
• hydroxytetracycline
• hydroxyzine
• hydroxyzine hydrochloride
• Hydrozoa
• hydrozoan
• Hydrus
• Hyemoschus