Bract Forms Waterproof Structure

close up view of a large deep purple flower petal with a brownish pistol

Biological Strategy

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Protect From Excess Liquids

While water is essential to life, too much water or other liquids can overwhelm living systems. Excess liquids can, for example, decrease a living system’s access to oxygen, promote excessive bacterial or fungal growth, or strip away soil and nutrients. To prevent the accumulation of excess liquids, living systems must control the movement of liquids across their boundaries or surfaces. They do so using waterproofing materials or structures, slowing flow, and/or facilitating flow to move the liquid away. Plant leaves, for example, commonly have waxy surfaces comprised of water-repelling chemicals to keep water from engorging the leaves or facilitating bacterial and fungal growth.

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Flowering Plants

Clade Angiosperms (“receptacle seed”): Dandelions, oaks, grasses, cacti, apples

With 416 families containing some 300,000 known species, angiosperms are the most diverse group of plants, and they can be found around the globe in a wide variety of habitats. They are characterized by seeds that grow enclosed in ovaries, which are enclosed in flowers. The floral organs then develop into fruits of myriad kinds and dimensions, from simple seed casings on maples to elaborate fleshy growths like papayas. The oldest flower known from fossils, Montsechia vidalii, appeared during the Jurassic Period 130 million years ago. They are the primary food source for herbivorous animals, which in turn makes them the indirect food source for carnivores as well.

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The spadix of the titan arum plant is protected from water by a specialized bract called a spathe, that clasps the spadix tightly enough to form a waterproof bag.

“The tall grey spadix [of the titan arum], which is filled with cobweb-like support fibres, becomes flaccid, topples forward and droops over the margin of the spathe. The spathe itself contracts inwards and its upper margins start to twist round the lower part of the spadix, clasping it so tightly that a huge water-tight bag is created. Safe inside it, the ovaries of the fertilised female flowers begin to swell.” (Attenborough 1995:136)

Last Updated August 18, 2016

References

Book

The Private Life of Plants

BBC Books | 21/08/1995 | David Attenborough

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