COLD ACCLIMATION OF SUSPENSION CULTURES OF ACACIA MEARNSII WILD

Suspension cultures of Acacia mearnsii Wild were prepared from callus.Six different experiments were made:(a) The suspension were placed at 25℃ in a LD of 16h for 14d:(b) The suspension were placed at 25℃ in a SD of 8h for 14d:(c) The suspension were placed at 2℃ in a LD of 16h for 14d:(d) The suspension were placed at 2℃ in a SD of 8h for 14d;(e) The suspension were placed at 25℃ in a LD of 16h for 7d followed by placing it at 2℃ in a SD of 8h for 7d:(F) The suspension were placed at 2℃ in a SD of 8h for 7d followed by placing it at 25℃ in a LD of 16h for 7d.The survival percentage of suspension cultures exposed to different conditions were measured by plasmolysis of cell.These results indicated that nonacclimated suspension cultures (i.e.with a LD of 16h and 25℃ treatment) showed a survival temperature of -2.5℃ and a SD of 8h for 14d or a LD of 16h at 2℃ for 14d also gave a survival temperature of-2.5℃ However, when the suspension cultures were exposed to a SD of 8h at 2℃ for 7d or 14d, the survival temperature went from-2.5℃ to -5.5℃ for 7d of acclimation, and to-7.5℃ for 14d.The suspension cultures responsed only to the combined SD and 2℃treatment.An increased freezing survival by individual stimuli (light or temperature alone) was not possible.It was necessary that both SD and temperature of 2℃ were at the same time to increase freezing survival.