Sugar and starch metabolism during ex vitro rooting and acclimatization of micropropagated Spathiphyllum `Petite' plantlets were studied to uncover in what way photosynthesis and carbohydrate reserves, accumulated during tissue culture, sustain plantlets regrowth and root formation. We followed carbon partitioning between sugars (sucrose, glucose and fructose) and starch and the changes in the activities of the key enzymes involved, including sucrose-P-synthase, sucrose synthase, acid invertase and ADPG pyrophosphorylase. It was concluded that during acclimatization of tissue cultured Spathiphyllum plantlets, photoassimilates accumulate before root emergence. Afterwards, carbohydrates were mainly translocated to these growing sinks. This was supported by the elevated levels of sucrose metabolising enzymes. Sink demands at the end of the light period gradually became saturated when plants were fully acclimatized, This resulted in a down regulation of sucrose-P-synthase and an activation of ADPG pyrophosphorylase, and at that moment a further starch accumulation started.