The present study aims at assessing the role of stored carbohydrates of F benjamina L. and F binnendijkii (Miq.) Miq., two tropical trees of horticultural significance, during acclimation to very low light intensities. Plants were grown at an average photosynthetic photon flux density (PPFD) of 90 mu mol m(-2) s(-1), and then transferred to a low-light treatment, with a PPFD of 5 mu mol m(-2) s(-1). Plants of both species showed negative growth rates for approximately 1 week, coinciding with a substantial decrease in the levels of total non-structural carbohydrates (TNC; starch and soluble sugars) in leaves and stems. TNC reached much lower levels in developing leaves than in fully grown leaves, and some of these developing leaves were shed in F benjamina. In stems and leaves combined, TNC levels were 142 mg g(-1) (plant) in F benjamina and 160 mg g(-1) (plant) in F binnendijkii at the time of transfer to low light. Thirty days later, in fully acclimated plants, these levels had stabilised at 116 and 112 mg g-'.The relatively minor damage to the plants and short duration of a negative carbon balance, despite the low mean PPFD 5 mu mol m(-2) s(-1), illustrate the capacity of both F benjamina and E binnendijkii to tolerate deep shade. Stored carbohydrates are important in plants that grow in environments like forest understories or indoor environments, where carbon balance can be negative for several days. (C) 2004 Elsevier B.V. All rights reserved.