SUGAR AND STARCH METABOLISM DURING EX-VITRO ROOTING AND ACCLIMATIZATION OF MICROPROPAGATED SPATHIPHYLLUM PETITE PLANTLETS

Sugar and starch metabolism during ex vitro rooting and acclimatizatio n of micropropagated Spathiphyllum 'Petite' plantlets were studied to uncover in what way photosynthesis and carbohydrate reserves, accumula ted during tissue culture, sustain plantlets regrowth and root formati on. We followed carbon partitioning between sugars (sucrose, glucose a nd fructose) and starch and the changes in the activities of the key e nzymes involved, including sucrose-P-synthase, sucrose synthase, acid invertase and ADPG pyrophosphorylase. It was concluded that during acc limatization of tissue cultured Spathiphyllum plantlets, photoassimila tes accumulate before root emergence. Afterwards, carbohydrates were m ainly translocated to these growing sinks. This was supported by the e levated levels of sucrose metabolising enzymes. Sink demands at the en d of the light period gradually became saturated when plants were full y acclimatized, This resulted in a down regulation of sucrose-P-syntha se and an activation of ADPG pyrophosphorylase, and at that moment a f urther starch accumulation started.