Weed Watcher

Plantago lanceolata may be a weed, but Deborah Roach sees heaven in this wildflower. To the bemusement of some farmers and the outrage of those who wage war against this species in their lawns, she has actually planted the alien perennial—30,000 of them, in fact—to find out what they can teach us about aging.

“We’re trying to understand mortality patterns at the latest stages of life and trying to see what shapes those patterns,” she said.

Biologists around the world are challenging the logical and long-held assumption that one’s chances of dying increase exponentially with age. Roach, an assistant professor of biology, described research with fruit flies that has actually demonstrated this is not the case. It’s been shown that after a certain point—for humans that seems to be about age 85 or 90—aging starts to slow down. By about age 110, the human mortality rate actually levels off. (The bad news is this rate is still about 50 percent.)

In a naturalized meadow about the size of two football fields at Shadwell, Thomas Jefferson’s birthplace, Roach has a grid of four successive plantings of Plantago. Once a month during the school year and daily in the summer, she and her crew of student helpers measure the lengths of the long, lance-shaped leaves and record the appearance of new ones, observe the number of spiking stems topped with nondescript white flowers and evaluate the quality and quantity of their seeds, and note the number of plants that have not survived.

Roach knows the parents of each plant, because she grew these seedlings in the greenhouse. She knows how old each is and how much each has reproduced. She knows the weather conditions and what other species in the environment may be shading or competing with her experimental subjects. With all this information, Roach hopes to tease out the part of the process that accurately reflects aging. 

“I’m an evolutionary biologist, so I’m trying to understand why aging should even exist. It doesn’t make sense. Natural selection is supposed to create organisms that are well adapted to their environment and can, therefore, reproduce a lot and live for a long time.”

To evaluate mortality patterns in an aging population, though, Roach needs a lot of plants. Enough so that, even after half the population dies within the first two years and natural phenomena—including the drought three years ago and the cool, wet summer the following year—take out another chunk, a significant number reach old age. The maximum life span reported for this species is seven years, but Roach believes many of her plants will outlive that expectation.

In her quest to understand aging, Roach may, in fact, have stumbled on the secret of immortality. “With my plants, there’s reason to think that maybe aging doesn’t occur,” she said, indicating a key difference between plants and animals: the ability to continue growing throughout their lives.

Although most animals have achieved their maximum size by the time they reach reproductive maturity, that’s not the case for plants. Plants often continue to grow new leaves and get larger even after they get older, even after they produce flowers and seeds.

“This is one of the things I find exciting,” said Roach. “It was one of these discoveries where I set off to do the work for one reason, and suddenly I’m finding there are other applications that challenge the assumptions we have about why organisms age.”

This article originally appeared in the July 2005 issue of the Arts & Sciences magazine.