How do the first flowers emerge?

Before flowering plants appeared, the gymnosperms, which have cone-like structures instead of flowers, dominated the plant kingdom

Hyderabad: Charles Darwin, the naturalist whose scientific theory of evolution by natural selection became the foundation of modern evolutionary studies, described the sudden origin of flowering plants, which emerged about 130 million years ago, as an abominable mystery. In all cases, the flower is responsible for a massive burst of evolution that has resulted in as many as 400,000 angiosperm species.

Before flowering plants emerged, the gymnosperms, which have cone-like structures instead of flowers, dominated the plant kingdom. These include pine trees and sago palms. Gymnosperms’ fossil record is about 360 million years old, which means they appeared on the Earth more than 200 million years before the angiosperms.

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The scientists believe that the first flowering plants evolved from gymnosperms and then developed into the diversity of flowering plants. A study by the Florida Museum of Natural History compared the genetic structure of two different flowering plants —  a small flowering plant and an avocado tree.

The flower of the avocado tree was found to be a genetic fossil, still carrying genetic instructions that would have allowed for the transformation of cones into flowers.

Advanced angiosperms have four organs: female organs (carpels), male organs (stamens), petals (colourful), and sepals (green). Basal angiosperms have three: carpels, stamens, and tepals, which are petal-like structures. The researchers expected each type of organ in avocado flowers would have a unique set of genetic instructions. Instead, they found the genetic instructions showed significant overlap among the three organ types.

With these facts established, the researchers feel, we can now think about the vast space open to natural selection to establish ever more rigid borders. The selection process arrived at a narrow solution in terms of four discrete organs but with a fantastic diversity of organ numbers, shapes, and colours that provide the defining phenotypes of each flowering plant species, say researchers.

Though researchers don’t know exactly which gymnosperms gave rise to flowering plants, previous research suggests some genetic program in the gymnosperms was modified to make the first flower.

A pine tree produces pinecones that are either male or female, unlike flowers, which contain both male and female parts. But a male pinecone has almost everything that a flower has in terms of its genetic wiring. Similarly, survivors like avocados represent a crucial link to the first flowers.