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Flower Power

Growing in the rain forests of Borneo and Sumatra are some very unusual parasitic plants that produce the largest individual flowers so far discovered.

These flowers can be over 1 meter (3 feet) wide and weigh over 9 kilograms (20 pounds).

This flower also has a very strong and horrible odor of decaying flesh. Because of this, some call it by the nickname “corpse flower”.

And what may be even more remarkable is that the plant species that produces such huge “corpse flowers” lacks any observable leaves, stems or even roots.

This is because this plant is a so-called holoparasite on other plants. That is, it’s completely dependent on its host plant for water and nutrients.

The name of this parasitic plant with the world-class flower is Rafflesia arnoldii.

Although these plants were originally described nearly 200 years ago, botanists have been unable to answer many basic questions about them, including how such huge flowers develop.

Until now….

A team of scientists, led by researchers at Harvard University, have been studying the flower development of Rafflesia and of a closely-related plant, Sapria. (Both are members of the quite remarkable plant family Rafflesiaceae.)

What they found surprised them:
Harvard researchers have solved the nearly 200-year-old mystery of how Rafflesia, the largest flowering plants in the world, develop. Rafflesia and Sapria closely resemble one another yet are actually built in fundamentally different ways, noted Harvard Professor Charles Davis. While the study sheds new light on how these plants develop, Davis said it may also help to explain how Rafflesia in particular attained such huge flowers.” (from Ref. 1 below)

The significance of these results?:
Rafflesiaceae produce the world’s largest flowers, but the developmental nature of their floral organs has remained a mystery. Most members of the family have a large floral chamber, which encloses their reproductive organs. We used comparative studies of development and gene-expression patterns to investigate the homology of their floral organs. Our results demonstrate that the similar floral chambers in two Rafflesiaceae subclades are constructed very differently. Thus, the characteristic features that define the floral chamber in these closely related clades are not homologous. Instead, these data indicate that similar floral chambers represent two distinct derivations of this morphology, which may have contributed to the explosive growth in floral diameter that arose secondarily within one subclade, Rafflesia.“. (From Ref. 2 below)

And now, a close encounter with a Rafflesia, thanks to YouTube:

References

1. Reuell, P. (2013) “Stages of bloom: Researchers unravel mystery of how world’s largest flower develops.” Harvard Gazette, November 4, 2011. (Full Text)

2. Nikolov, L. A., P. K. Endress, M. Sugumaran, S. Sasirat, S. Vessabutr, E. M. Kramer, and C. C. Davis (2013) “Developmental origins of the world’s largest flowers, Rafflesiaceae.” Proceedings of the National Academy of Sciences (USA), doi: 10.1073/pnas.1310356110. (Abstract)

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