How do clover leaves fold at night without muscles?
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Answer: Clock-controlled changes in water pressure move cells at the leaf base
Clock-controlled changes in water pressure move cells at the leaf base ✓ — Cells in the swollen joint at a clover leaflet’s base change their water content and pressure, moving the leaflet. An internal daily clock helps time this movement. Its possible benefits, including effects on temperature or herbivores, are separate questions and are not settled by knowing how it moves.
The whole leaf wilts from dehydration and recovers only after morning dew — Clover’s nightly folding is not ordinary dehydration of the whole leaf. Specialized cells at the leaflet base change water pressure in a controlled pattern, allowing reversible movement without waiting for dew.
Nighttime growth on one side bends the leaf stalk — This repeated clover-leaf movement is not driven by fresh unequal growth of the stalk each night. Pressure changes in the joint’s cells allow the same leaf to fold and reopen without lengthening the stalk on alternate sides.