This thistle remains cool to the touch even in the heat of summer.

In the sunny mountains of southern Spain, a type of thistle appears to have its own built-in air conditioning system.

The flowers of this plant, known as Carlina Colinbose, Stay cooler than the hot air around you. According to ecologist Carlos Herrera, the flowers maintain an average temperature about 3 degrees Celsius (5.4 degrees Fahrenheit) cooler than the surrounding air. During the hottest part of the day, the temperature difference can be even greater, with the flowers reaching temperatures as low as 10 degrees Celsius (18 degrees Fahrenheit).

Even when the air temperature soars to 45 °C (113 °F), the plant’s flowers can remain relatively cool at 35 °C (95 °F). Herrera presented his findings on February 13th in the field of ecology.

“This significant cooling effect compared to the surrounding air is quite remarkable,” says ecologist Christopher Still of Oregon State University in Corvallis. While he was not directly involved in the study, Still praises it as a thorough and insightful research endeavor.

Accidental Discovery

In Spain’s Cazorla Mountains, scorching summers have taken a toll on many plants, leaving them dead, dry, or inactive. Amidst the sea of brown, a yellow thistle stands out with its vibrant flowers blooming above the lifeless landscape.

During a recent journey through the mountains, Herrera was surprised to find that the thistle flowers felt cool to the touch, even in the heat of the day.

While Herrera works at the Spanish National Research Council in Seville, he was in the mountains studying the plant-pollinator relationship in the region. His curiosity was piqued when he felt the coolness of the thistle flower and decided to investigate further.

Using an electric thermometer, Herrera measured the temperature of seven thistles at two different locations, checking each flower multiple times on various days. As the days grew hotter, the flowers consistently maintained a cooling effect.

Most studies on plant cooling have focused on leaves, with little research done on how flowers maintain a lower temperature. According to Herrera, thistle flowers exhibit a more significant cooling effect compared to leaves and other plant parts.

Causes of Coldness

The unique shape and structure of thistle flowers are believed to play a key role in their cooling mechanism. Herrera speculates that as water evaporates from inside the thistle, it removes heat, preventing the flower from absorbing the warmth of the sun and causing it to cool below the ambient air temperature. He refers to this phenomenon as the “Botillo effect,” likening it to the cooling process observed in porous clay water jugs.

Herrera and Still aim to explore how thistles benefit from maintaining a cooler environment than the surrounding air. They plan to investigate if the cooling effect attracts pollinators seeking relief from the intense summer heat and to determine if other thistles in southern Spain exhibit similar cooling properties. Additionally, they intend to conduct experiments to analyze how a reduction in water availability affects the cooling process in these plants.

While observing the natural world can yield valuable insights, Still emphasizes the potential for Herrera’s study to spark further research and discoveries in the future.

Source: www.snexplores.org