Researchers grew plants from seeds and scanned them to see how their architectures develop. Image credit: Salk Institute Researchers at Salk Institute have found that growing plants have the same universal design principles that humans use to engineer transportation networks, such as subways.

Using 3D laser scans, Salk was able to determine that, like a subway system where the main objective is to get people from the suburbs to downtown as quickly as possible, the plant base is the downtown and its leaves are like the suburbs. Nutrients need to get between these areas as quickly as possible, while at the same time limiting the cost of growing extraneous branches.

The research team examined three crops: sorghum, tomato and tobacco. They grew the plants from seeds under conditions that the plants might experience naturally, including shade, ambient light, high light, high heat and drought. Every few days for 20 days, the team scanned each plant to capture its growing network of branches, stems and leaves.

"Scanning plants in three dimensions can be fairly time consuming," says Adam Conn, a Salk research assistant. "But it's non-invasive, and once you've done it you can discover things from the data that you couldn't learn by just looking at the plants."

From the scans, Salk researchers were able to extract coordinates corresponding to each plant’s base and leaves in 3D space. These coordinates were used to create and graph theoretical plant shapes that prioritize either efficient routes for nutrients, minimal branch length or various tradeoffs between the two.

Much like transportation networks, the results were that plants' networks of branches found the best balance between cost (branch length) and performance (nutrient delivery) for their particular environment.

"Our hypothesis was that if total length and travel distance were important evolutionary criteria for plants, there would be evolutionary pressure to minimize the criteria together, and that's actually what we found," says Ullas Pedmale, who was a postdoctoral researcher on the project at Salk.

Researchers found that the plants clustered by species and they made different tradeoffs based on their growth environment. Tomatoes generally maintained a balance between cost and performance but those grown in high light found a different balance than those grown in low light.

"This means the way plants grow their architectures also optimizes a very common network design tradeoff. Based on the environment and the species, the plant is selecting different ways to make tradeoffs for those particular environmental conditions," says Saket Navlakha, assistant professor in Salk's Center for Integrative Biology. "By understanding these tradeoffs we may be able to dynamically tune our crop varieties to a changing climate."

The full research can be found in the journal Cell Systems.