Freezing Tolerance and Rapid Cold Acclimation of Spinach

Abstract

Abstract Freezing tolerance and rates of acclimation and deacclimation were determined for three Chinese spinach (Spinacia oleracea) cultivars (‘Harbin’, ‘Beijing’, and ‘Shantung’) and one American spinach cultivar (‘Bloomsdale’). Detached leaf and whole plant freezing tolerances were compared during cold acclimation. Freezing tolerance of detached leaves was equivalent to the freezing tolerance of whole plants. Using detached leaves, freezing tolerance of the cultivars was determined after 0, 1, 3, 7, 14, and 21 days of cold acclimation at 5°/2°C (day/night temperature) and then after 1, 3, and 7 days of deacclimation at 20°/17°. All four cultivars acclimated and deacclimated very rapidly. Depending on the cultivar, a 2° to 4° increase in freezing tolerance was observed after 1 day of acclimation. The greatest change in freezing tolerance occurred in the first 3 days of acclimation. The rate of acclimation diminished dramatically after 3 days, and there was little change in freezing tolerance after 14 days of acclimation. Upon exposure to deacclimating temperatures, fully acclimated plants lost 3° to 5° freezing tolerance within 1 day. There was no further decline in freezing tolerance after the 3rd day of deacclimation.