Leaf Temperature Regulation Offers Promise for Refining Earth System Models

The thermal traits of a leaf, critical for photosynthesis, may be under strong evolutionary selection that occurs in response to environmental temperatures. Here a thermal leaf image details temperature variation, which greatly affects plant functions since temperature is closely linked to metabolic kinetics—the plant’s pathways and speed of reactions that support growth and other functions essential for survival. (Credit: Benjamin Blonder)

A recent study has discovered that plants can control their leaf temperature with some independence from the surrounding air temperature. This trait in plants will help them to increase carbon uptake through photosynthesis.

This research has the potential to refine Earth system models and promises to help predict impacts of climate impacts and feedbacks.

This research combines theory for leaf energy flows with globally distributed temperature data for diverse plant taxa to show that leaves generally do not match air temperature, but instead thermoregulate. The end result is that leaves are generally warmer than air in cold temperatures, and cooler than air in warm temperatures.

Sean Michaletz, Plant Ecologist, Los Alamos National Laboratory

As part of the mission to sustain the nation’s energy security, Los Alamos studies and models climate change, and the impacts related to it.

Michaletz and co-researchers have developed a novel theory, taking into account energy budgets that are responsible for the intake and outtake of thermal energy fluxes in a leaf, along with the carbon economics theory, which proposes that a leaf’s form and function is totally dependant on a leaf structure’s efficiency to process carbon.

The team of researchers demonstrated how thermoregulation will help to maximize leaf photosynthesis, and also showed the total lifetime carbon gain of a leaf. A report on this research has been published in the recent issue of Nature Plants.

This newly developed theory will play a vital role in the development of a more significant plant ecology that will help examine the origins of leaf thermoregulation. It will also help to analyze the process where leaf temperature differs from ambient air temperature.

The research further highlights that plant functions are decoupled from ambient temperatures, a finding that will help to improve climate models.

Almost all of the plants photosynthesize - they convert light energy and CO2 from the atmosphere into sugars that later form roots, stems, and leaves. Leaf thermoregulation is vital for plant carbon economics as leaf temperatures help to determine the speed of respiration and photosynthesis.

As it is assumed that plants function based on the temperature of the environment, most of the currently used Earth system models that predict plant-atmosphere feedbacks also assume that plant physiology function at the ambient air temperature. However, according to the results obtained from this research, leaf temperature can be drastically different from air temperatures.

This disassociation weakens the link between plant functions and climate, limiting carbon budgets of an ecosystem and climactic impacts on plant growth.

This research was conducted by Michaletz and co-workers at the Laboratory's Earth and Environmental Sciences Division, with a motive of identifying a connection between plant physiology rates, plant traits, and climate.

Michaletz, a Los Alamos Director’s Postdoctoral Fellow, and his mentor Nate McDowell presented this research in Nature Plants paper by teaming up with authors from the University of Arizona, University of Oklahoma, Tsinghua University, Lawrence Berkeley Laboratory, Smithsonian Tropical Research Institute, University of Pennsylvania, The Santa Fe Institute, The iPlant Collaborative, and Aspen Center for Environmental Studies.

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