in leaves and isolated thylakoids from spinach

摘要: Frost hardiness of spinach (Spinacia oler acea L.) leaves was increased by high concentra tions NaCl in the hydroponic culture medium. Freezing damage determined measurement slow chlorophyll fluorescence quenching after freezing leaves. Both osmolality leaf sap and frost were linearly correlated with salt concentration hydro ponic occurred, irrespective extent hardening, when dehydration cells during extracellular ice forma tion decreased cellular volume to approximately 14% unfrozen cells. The resis tance isolated, washed thylakoids against me chanical chemical vestigated. Chemical caused accumulation measured as release chloroplast coupling factor (CF1 ; EC 3.6.1.3), mechanical lumenal protein plastocyanin from membranes an in-vitro freeze-thaw cycle. Isolated thy lakoids salt-treated frost-hardy those plants hardened under natural condi did not exhibit improved tolerance stress exerted con centrations. They were, however, more hardy than unhardened control freezing.