Relationship Provides Thermal Protection

Biological Strategy

Hot springs panic grass

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Image: James St. John / Wikimedia Commons / CC BY - Creative Commons Attribution alone

Protect From Temperature

Many living systems function best within specific temperature ranges. Temperatures higher or lower than that range can negatively impact a living system’s physiological or chemical processes, and damage its exterior or interior. Living systems must manage high or low temperatures using minimal energy, which often requires controlling responses along incremental temperature changes. To do so, living systems use a variety of strategies, such as avoiding high or low temperatures, removing excess heat, and holding heat in. Insulation is a well-known example of managing low temperatures by retaining heat using thick layers of hair, fur, or feathers to hold warm air next to the skin.

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Cooperate/Compete Between Different Species

From parasitism to mutualisms, there are endless interactions between organisms in nature. Interactions between species that lead to a negative outcome for one species are known as competition. Cooperation occurs when organisms work together for the benefit of each organism or species. While competition often occurs over resources or mates, the more biologists have begun to look for examples of cooperation in nature, the more they have found. For example, around 90% of plants have a beneficial partnership with fungi. Fungi provide the plant with nutrients such as nitrogen and phosphorus, in exchange for sugars from the plant.

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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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Hot springs panic grass and Curvularia fungus are protected from extreme heat thanks to their mutualistic relationship.

Hot springs panic grass (Dichanthelium lanuginosum) appears to tolerate the high temperatures of Yellowstone’s geyser basin because of a fungus that attaches to the plant and lives between its cells. Researchers cultivated specimens with and without the fungus, called Curvuluria, then heated the soil. They found that, while plants with the fungus survived to 149 degrees F, plants lacking the fungus shriveled at 122 degrees. More experiments showed that the plant provided thermal protection for the fungus, as well. (Courtesy of the Guild)

“All plants studied in natural ecosystems are symbiotic with fungi, which obtain nutrients while either positively, negatively, or neutrally affecting host fitness. Plant to selective pressures is considered to be regulated by the plant genome. To test whether mutualistic fungi contribute to plant adaptation, we collected 200 Dichanthelium lanuginosum plants from geothermal soils at 10 sites in Lassen Volcanic (LVNP) and Yellowstone (YNP) National Parks. These soils have annual temperature fluctuations ranging from about 20° to 50°C…In the absence of thermal stress, endophyte-colonized (symbiotic) and endophyte-free (nonsymbiotic) plants showed no measurable growth or developmental differences. When root zones were heated with thermal tape (Fig. S1), nonsymbiotic plants (45/45) became shriveled and chlorotic at 50°C (Fig. 1A). In contrast, symbiotic plants (45/45) tolerated constant 50°C soil temperature for 3 days and intermittent soil temperatures as high as 65°C for 10 days. All nonsymbiotic plants (45/45) died during the 65°C heat regime, whereas symbiotic plants (45/45) survived. The endophyte was reisolated from surface sterilized roots and leaves of all surviving plants, indicating that both the fungus and the host were protected from thermal stress. [Note: similar results were found when testing seedlings returned to the hot springs area.]…In addition to thermotolerance, the basis of mutualism in this system may involve other benefits (e.g., nutrient acquisition by the fungus). Several possible symbiotic mechanisms could confer thermotolerance. In planta, the fungal endophyte produces cell wall melanin (Fig. S3) that may dissipate heat along the hyphae and/or complex with oxygen radicals generated during heat stress. Alternatively, the endophyte may act as a “biological trigger” allowing symbiotic plants to activate stress-response systems more rapidly and strongly than nonsymbiotic plants.” (Redman et al. 2002:1581)

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