Grass leaf size provides a better understanding of climate change vulnerability

UCLA researchers Alec Baird, Lawren Sack and colleagues have discovered that small grass leaves can photosynthesize more efficiently and that a special vascular system can withstand cold and drought. Credits: Alec Baird / UCLA

One-third of the Earth’s surface is covered with over 11,000 grass species, including crops such as wheat, corn, rice and sugar cane, which account for most of the world’s agricultural production and important biofuels. However, grass is so common that few people realize that it is really diverse and important.

Studies published in the journal today Nature It not only improves crop design, but also provides insights that scientists can use to more accurately model the effects of climate change. It also provides new clues that may help scientists use fossil leaves to better interpret the climate of the ancient past.

The lead author of this study is Lauren Sack, a professor of ecology and evolutionary biology at the University of California, Los Angeles, and one of the most influential scientific researchers in the world.

Studies have determined that grasses with narrow leaves and a large number of veins should be able to tolerate drier conditions better than expected in the future. This discovery should allow scientists to more accurately predict the ability of grass species to withstand cold and drought, which are important for species protection in climate change. Scientists growing agricultural grasses to withstand cold climates and droughts also suggest that varieties with small leaves and large veins should be focused.

From other types of plants, scientists have learned that leaf size is an important factor in how plants adapt to their environment. However, until now, it was unknown how thousands of varieties of grass exist in so many diverse environments, and whether leaf size plays a role.

“The size of the grass leaf blades varies from a few square meters of grass in the highlands of the Andes to over a square meter of tropical bamboo,” says Sack.

Sack, UCLA PhD student Alec Baird, and other scientists in the United States and the United Kingdom have edited a database of grass blade sizes, unique climate, and evolutionary relationships around the world. They found that small grass leaves predominate in dry, cold environments.

This is due to the filtering of grass species that have spread throughout the tropics and large leaf seeds from hot, dry summer or cold winter locations, says Baird, the lead author of the study.

Small leaves are beneficial to plants because they accumulate a thin layer of static air that covers the surface more than large leaves. It helps them cool faster on hot days and not on cold nights, Sack explained.

Grass leaf size provides a better understanding of climate change vulnerability

Enlarged image of chemically transparent and stained wheat leaves. It shows a complex venous system. Credits: Christine Vuong / UCLA

The study also revealed new insights into the leaf venous system and how small grass leaf veins specifically provide cold and drought tolerance.

The veins distribute the nutrients and water that the leaves need for photosynthesis. This is the ability of plants to convert sunlight and carbon dioxide into sugar. Studies of other types of plants have shown that when the leaves are newly formed, they make the first veins, and as the leaves expand, those veins are placed further apart, Sack said. It was. As a result, large leaves have fewer large veins in a particular area and are more vulnerable to stress than smaller leaves.

The number of veins is important because in order for any plant to grow, the leaves use openings called stomata on their surface to capture carbon dioxide. However, opening those pores exposes the moist interior of the leaves and the plant loses a lot of water by evaporation. To replace that water, the plant draws water from the soil through veins in the roots, stems, and leaves within a pipe-like structure called the xylem.

However, if the soil becomes too dry or cold, or if the xylem pipes freeze, bubbles can form and prevent water from spreading throughout the plant. Studies of plants other than grass have shown that small leaves with more veins are less problematic because there are enough veins to pump water around such obstructions.

“But it wasn’t clear why small-sized grasses had any of these advantages known for the leaves of other types of plants,” Baird said. “Most grass leaves, on average, are already hundreds of times more than typical flowering plant leaves, not like trees, but have a parallel venous system.”

Researchers have measured the venous system of the grass thousands of times and used computer models to determine the effects of grass leaf size and venous properties on how efficiently each species performed photosynthesis. I looked it up.

“There are numerous variations in the structure of grass blades, but overall small grass blades are packed together with dramatically more large veins than large grass blades, making them resistant to drought and freezing. I knew I would offer it, “Baird said. “The smaller the leaves of the grass, the more likely they are to contain smaller pipes inside, which can withstand the blockage of air.”

Sack uses mathematical formulas devised by scientists as part of his research to estimate the size of intact grass leaves from the fragmentary debris of fossil layers dating back tens of millions of years, and they estimate it. I grew it.

“Everything we learn about grass has important value for our food and ecosystem,” he said. “The poet Walt Whitman pointed out the vast amount of knowledge that people can learn while thinking about the leaves of grass. These new discoveries are learning lessons from trillions of leaves of grass around the world. I think he is happy. ”

Studies show how plants evolve for faster growth

For more information:
Alec S. Baird and other developmental and biophysical determinants of grass leaf size around the world, Nature (2021). DOI: 10.1038 / s41586-021-03370-0

Courtesy of the University of California, Los Angeles

Quote: The size of the leaves of the grass is the climate change (2021, 3) obtained from on March 25, 2021. Provides a better understanding of vulnerabilities to (25th May)

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Grass leaf size provides a better understanding of climate change vulnerability

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