Flowers' Unseen Colours Can Aid in Pollination & Survival

Different substances in flower petals create a "bulls-eye" for pollinating insects, according to a Clemson University scientist whose research sheds light on chemical changes in flowers that help them respond to environmental changes, including climate change, that may threaten their survival.

Matthew H. Koski, an assistant professor of biological sciences at the Clemson College of Science, led a research team that studied the bright, yellow flowers of Argentina anserina—a member of the rose family commonly known as silverweed—to learn how pigments in the petals visible only in the ultraviolet spectrum play an important role in the plant's plasticity, or its ability to respond quickly to changing environmental conditions. The team also included Clemson researchers Lindsay M. Finnell, Elizabeth Leonard and Nishanth Tharayil.

Research Findings:

The researchers studied silverweed at various elevations in southwestern Colorado to better understand the roles of the various UV-absorbing chemicals in the plants' petals and how these chemicals work to aid in pollination and, thus, reproduction.

Although humans cannot see the UV patterns on the flower's petals, many of its pollinators can, according to Koski.

"I've always been fascinated with how [flower colour variation] arises, how it evolves, and what factors drive the evolution of colour variation," Koski explained, "so I became interested in thinking about how we perceive colour versus how organisms that interact with flowers more frequently perceive colour."

"Insects, for example, pollinators, see in the ultraviolet spectrum," he continued. "So, flowers that reflect or absorb ultraviolet wavelengths give (to pollinators) the perception of different colours that we can't see. I've been fascinated with uncovering what these UV signals might be doing functionally with respect to pollination. When I think about the trait of interest in ultraviolet absorption, it's biochemistry. It's a biochemical trait that leads to different perceptions of UV absorption and reflectance."

According to Koski, UV-absorbing chemicals are concentrated at the base of the flower's petals, while UV-reflecting chemicals are concentrated at the tips of the petals. According to him, this results in an overall "bulls-eye" effect that guides insects in their search for pollen.

The researchers wanted to learn more about how plants adapt to thrive in different environments—in this case, a 1,000-meter difference in altitude. They discovered that flowers at various altitudes adapt to their surroundings by producing varying amounts of UV-blocking or UV-absorbing chemicals.

"There are always more UV-absorbing compounds or a larger spatial area of UV absorption on the petals at higher elevations, compared to low-elevation populations," Koski explained.

This, according to the researchers, demonstrates the plant's plasticity, which Koski defined as how different traits emerge in the same organisms under different environmental conditions. This is an important step in understanding how organisms adapt to change.

"What's important about plasticity is that when we think about climate change and global change, plasticity is one mechanism by which natural populations can respond really quickly to changing climates and persist in those climates," he explained. "The process of evolution, in which changes in the genetic code occur over time, is thought to proceed more slowly than simply responding plastically to environmental change."

One question raised by the research, according to Koski, is whether plastic responses to environmental situations are adaptive. Do they provide any benefit to an organism, or are the changes in how a trait develops as a result of the environment that have no impact on plant fitness?

"One thing this study discovered is that the plastic change in UV pigmentation benefited the plant, particularly those at high elevations, because increases in ultraviolet absorption on the petals resulted in increased pollen viability," he said.

According to Koski, the research will help scientists better understand how organisms respond to environmental changes and even predict whether or not some organisms will be able to survive rapid environmental change, such as that caused by global climate change. He believes the research could be useful in agriculture because some of the UV-sensitive pigments found in silverweed are also found in commercial crops such as mustard and sunflowers.

(Source: Phys Org)