Cold storage of plant tissue cultures - effect of sucrose

Explants of normal (non-transformed) carrot ( Daucus carota L.) tissue, scorzonera crown gall ( Scorzonera hispanica L.) and carrot tissues transformed with Agrobacterium tumefaciens (all cultured in vitro ) were planted in little glass jars with 6 cm3 of nutrition media containing 3, 5, 7 or 9% sucrose and maintained at +3 ºC for 6, 8, 10 and 12 months. Viability of tissue cultures after cold storage was estimated by the degree of tissue necrosis, per cent of explants exhibiting growth resumption and intensity of the resumpted growth. Little or no growth was observed during cold storage of scorzonera and normal carrot tissues, whereas transformed carrot tissues showed significant growth. Dry matter content of tissues increased with an increase of sucrose concentration in the medium and failed to change during cold storage of scorzonera and normal carrot tissues. The dry matter content of the transformed carrot tissues fell down during cold storage due to the increase of fresh weight. The viability of all tissue cultures was preserved better and for a longer time with 7% sucrose, than with 3, 5 and 9%. Transformed carrot and tobacco callus tissues preserved cell viability better than non-transformed ones. Cycles consisting from long subcultures (several months) at 3 ºC interrupted by short subcultures (several weeks) at 26 ºC were applied in order to storage of tissue cultures for several years.