Solving the mystery of Myriocarpa flowers


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Composite image of the base of a female flower showing what we now believe are bracts at the base. Note the small stalked glands spaced evenly along each bract. You can see each cell in the flower thanks to the amazing imaging facilities at the Natural History Museum.

For over a hundred years the genus Myriocarpa in the nettle family which comprises ca 15 tree species in South and Central America has been impossible to place within the family. This is largely because of the very unusual shape of the part of the female flower that receives pollen, known as the stigma (see image below) and the fact that neither of the two great experts could agree over whether the petal-like structures at the base of the flower were petals associated with the flower, or bracts associated with the stalk. Whilst this might not seem like the stuff to keep a botanist awake at night it has become of interest again as using DNA data we have identified as sister to another small group of trees, Gyrotaenia, found in Cuba, Hispaniola, Jamaica and Central America that has a flower which consists of the petals fused to form a tube which is fused to ovary.

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The tip of the female Myriocarpa flower showing the very unusual forked stigma, the part of the flower which receives the pollen. You can see that it is covered in multicellular hairs, which are characteristic of the nettle family, and serve to capture pollen form the air and guide it to the stigma.

I was therefore very curious to see whether Vladimir Blagoderov, Manager of the Museum’s Sackler Imaging Suite could help me generate an image that would help us resolve the mystery. He could! The two images above are each composed of about 20 images which ‘slice’ through the sample which was of young flowers collected in alcohol in Belize over 10 years ago. The resolution was amazing, each cell being visible. In fact you could even make out the rough crystalline structure on the surface of the hairs! Both of these images also helped us to answer the question, revealing that this flower does indeed consist of a tube composed of fused petals that is subsequently fused to the ovary. This we could see in both images where the clearly visible ovary is enveloped by another distinct tissue, as in the case of Gyrotaenia. It was also confirmed by the petal-like bracts at the base of the flower having stalked glands, structures not known to occur on the ovaries of Urticaceae. So a morning’s work and an idea of evolutionary relationships enabled me to answer a question that had been frustrating an albeit very small group of botanists for over 100 years!

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Photograph of the string-like flower clusters of Myriocarpa longipes taken in Panama where it occurs as a small tree growing near rivers in tropical forest. Each flowers cluster consists of thousands of tiny flowers

 

 

The future climate of Amazonia

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The cover of Antonio Nobre’s report, a copy of which in English, Spanish or Portuguese can be obtained by clicking on the image above

 

At the Intergovernmental Panel on Climate Change (IPCC) conference in Lima this December, Brazilian researcher, Antonio Donato Nobre published a synthesis on the most recent scientific data about the Amazon’s climate accompanied by an explanation of the the profound impact that the Amazon has on South America and how this is changing as a consequence of climate change and deforestation. Antonio Donato Nobre, a well-respected Brazilian scientist and brilliant science communicator (click here to see his Ted Talk) has been researching the Amazon’s climate for decades.

The synthesis introduces two concepts that were new to me: the first was the notion of the Amazon as a ‘Green Ocean’, the second that the Amazon functions as a biotic pump pushing ca 20 billion tonnes of water into the atmosphere every day and in doing so drawing water vapour in from the Atlantic Ocean. The first idea of the Amazon as a Green Ocean is an important one as it gives a scale to the impact the Amazon has on the global climate, equivalent to one of the World’s Oceans. Conversely it also suggests the enormity of what we are doing to an ecosystem that is probably critical for our welfare. The second concept, not proven but for which there is mounting evidence, presents the Amazon as a vast community of ca 385 billion trees mutually interdependent with trillions of micro-organisms, insects and vertebrates functioning in concert as a water pump, extracting water from the ground, catalyzing its conversion to rain in the lower atmosphere and in doing so drawing water vapour in from the Atlantic Ocean and sending moisture to the grain belt of South America creating one of the most productive agricultural landscapes in the World.

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Diagram from Makarieva et al.’s article in the Journal of Hydrometeorology, 15, 411-426 (2014) summarizing the biotic pump, the product of the action of ca 385 billion trees. Precipitation in the lower atmosphere catalysed by volatile secondary plant chemicals released by leaves results in a drying of the air above which when rehydrated over the moist ocean carries water inland

 

The main points of Antonio’s report are that 1) the Amazon generates a climate that supports agriculture to its south, 2) deforestation will result in a climate that does no longer supports agriculture in southern South America, 3) that the nature of the Amazon’s impact on climate means that there is a point of no-return with respect to deforestation which once passed will lead irreversibly to desertification for much of southern South America, 4) that deforestation in the Amazon is already having an impact on the regions climate and that this could accelerate the impact of climate change on the Amazon, and lastly 5) it is not too late to reverse these impacts and that muscular actions to outlaw forest fires and deforestation coupled with a popularization of the scientific research on the Amazon cold avert the destruction of the Green Ocean. I can not recommend reading the report enough, it is engagingly and precisely written and will make you amazed at the impact forest have on our World.