Floral biology of cupuassu (Theobroma grandiflorum (Willdenow ex Sprengel) Schumann).
Cupuassu (Theobroma grandiflorum), one of the most profitable crops of
Amazonia, is now attracting world-wide attention as an exotic fruit, used in juices, ice
cream and sweets. It is a shade tolerant tree that can be grown as a component of
agroforestry systems. Nevertheless it is still a wild species and little is known about its
Floral biology of cupuassu was studied in Belem-Brazil during 2 floweringfruiting
seasons between June 1991 and December 1993.
Flowering occurs in the drier period of the year. Flowers commence opening at
any time of the day, but open fully at the end of afternoon. The anthers dehisce and the
stigmas are receptive as soon as the flowers are fully open. Stigmas remain receptive
until 10:00 am the following day. Throughout this period, the pollen grains remain
The flowers have a complex morphology which favours allogamy. The species
is also self-incompatible. Experimental pollinations, using compatible pollen grains,
have shown that a flower which receives 60 compatible pollen grains has 20%
probability of setting fruit; a flower which receives more than 400 pollen grains always
sets fruit. However, only around 2% of naturally pollinated flowers receive more than
60 pollen grains.
A stingless bee, Plebeia minima, is considered an effective pollinator of
cupuassu. Another stingless bee, Trigonisca pediculana, also visits cupuassu flowers.
Both bees are small insects, which are unlikely to fly very far. Ants (Wasmannia sp.)
and weevils (Baris sp.) were considered secondary pollinators, unlikely to promote
effective pollinationsFruits mature during the wet period of the year, approximately 5.5 months after
the flowers open. The limited and irregular fruit set is probably caused by scarcity of
The transformation of cupuassu to a plantation crop will therefore require
conditions which favour natural pollinators and their access to receptive and compatible