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Rainforests of the World 

May 5, 2011

First fruit on the Cacao Tree

Theobroma cacao with ripe fruit 

Photo by Kristen Natoli

Rainforest Biologists were very excited a few months back to discover a new fruit on the Cacao Tree (Theobroma cacao), the first fruit we have had on this tropical tree.  Originating in the Amazon headlands, Theobroma cacao is, of course, the source of one of our favorite foods, chocolate, which is made from the fermented and roasted seeds.

One of the most beautiful specimen plants in our collection, this tree has grown vigorously and flowered prolifically since it arrived but we were not sure we would ever see it fruit. 

 Lots of flowers on the Theobroma cacao trunk

Photo by Rachael Tom

 

Cacao trees typically don’t set fruit until they mature at about 5-10 years old.  Most Cacao trees are ‘self incompatible’ meaning they will recognize and reject their own pollen, preventing self pollination in order to maintain genetic diversity.   We were not sure our tree would ever fruit as it is the only plant of its kind in the exhibit. 

Theobroma cacao single flower

Photo by Rachael Tom 

 In the wild these trees are most often pollinated by midges in the Forcipomyia family.  As we do not have these insects in our exhibit our volunteer James has been patiently and diligently hand pollinating flowers each week. 

 Pollen collection from the Theobroma

Photo by Kristen Natoli

 hand pollinating the Theobroma

Photo by Kristen Natoli

At last we have success.  Amazing to think these large 6-8″ long fruits are produced from one flower only 1/2” in size.  The Cacao Tree produces flowers right off the main trunk of the tree, an adaptation called cauliflory.  This adaptation, mainly seen in tropical trees, likely serves to hold the fruit closer to the ground where the seed disperser animals are most active.

 fruit on Theobroma cacao

Photo by Rachael Tom

 

Besides being delicious the Theobroma cacao is a particularly pretty tree exhibiting many adaptations unique to the tropics.   The new growth on our specimen is a rich burgundy color from the concentration of anthocyanins in the leaf tissue.  This adaptation is likely a means of protecting tender new leaves from the intense tropical sunlight at canopy and deterring insect feeding. The lower leaves are broad and thin to maximize capture of the limited light penetrating the understory.  The smooth surface and vertical drape of the leaves ending in a pointed ‘drip tip’ help shed water during heavy rains. 

 New growth on Theobrom a cacao

Photo by Sarab Stewart

 

The seeds from our first fruit will be germinated to produce additional back up Theobroma plants as we are so pleased with how much the parent plant adds to the exhibit.


Filed under: Plants,Uncategorized — Paphiopedilum @ 6:07 pm

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