Mechanical freeze‐thaw damage and frost hardening in leaves and isolated thylakoids from spinach. II. Frost hardening reduces solute permeability and increases extensibility of thylakoid membranes

Thylakoids isolated from cold‐acclimated spinach ( Spinacia oleracea L. ) leaves were more resistant against mechanical freeze‐thaw injury measured as plastocyanin release, than thylakoids from non‐acclimated leaves. They were more resistant against solute influx during freezing and they were able to re‐expand to a larger volume in comparison to non‐hardy controls. Likewise, plastocyanin was released from thylakoids of non‐acclimated but not of frost‐hardy leaves under conditions of mild in situ freezing stress for several days.