On May 1st, 2018 we learned about

Some perennial plants can stay dormant for up to two decades

Spring is upon us, and all kinds of organisms are waking up from some form of dormancy or another. Frogs are thawing out their chilled bodies, bears are ending their hibernation, and perennial plants are regrowing lost leaves and stems. In most cases, this cycle is consistent and necessary, after all, a bear can’t store enough fat in its body to keep it alive for over a year of hibernation. However, scientists have found that at least 114 species of plant don’t need to follow this seasonal schedule. Instead of popping up each spring, their root stock can remain dormant underground for as long as 20 years without a problem.

At least the plants would hope there’s not a problem. Taking a break from normal growth cycles is risky- the plants can’t gather sunlight for photosynthesis, and they can’t create seeds or suckers to reproduce while dormant. Some of those concerns are mitigated by finding alternative sources of nutrition, such as gathering carbohydrates from fungi living in the soil, but the overall strategy is still a bit of a gamble. In going dormant for years at a time, a plant is essentially betting that its local environment will somehow be easier to live in years into the future, even though there’s no real way of knowing that.

Skipping threats, not seasons

Since all perennials go dormant during winter months when conditions are tough, researchers assumed that these multi-year periods of dormancy were just an extension of seasonal coping mechanisms. As such, they figured that they’d find more dormant plants in northern climates than at the equator, since seasonal conditions were more dramatic in those places. Instead, they found the opposite- mild winters and warmer climates actually had more plants sitting things out for years at a time, pointing a completely different set of influences.

In warmer, more equatorial regions, plants seemed to be going dormant to avoid less predictable threats than seasonal change. Disease, fires, predation from animals and competition with other plants were all tied to differing lengths of dormancy. In some cases, the threats were localized enough that a single species would stay dormant in one region longer than it would in another, again suggesting that plants were reacting to their local experiences over larger, systematic forces. From that context, the potential benefits of an extended dormancy start to look a bit clearer. Remaining dormant through dry, hot fire seasons may let a root stock regrow in an area suddenly soaked in the burnt but nutritious remains of what used to be competing species.

Widespread survival strategy

While some species of plants, like orchids, seem to have a bit of an affinity for this survival strategy, many species have evolved the ability for going dormant beyond a single winter. Since this trait is spread across many plant family trees, it’s thought that it must have evolved more than once, as a case of convergent evolution. Researchers also suspect that it’s an easy adaptation to acquire, possibly only requiring mutations in a few genes, although at this point the exact physiological and genetic mechanisms at play haven’t been directly identified.

Source: 'Rip Van Winkle' plants hide underground for up to 20 years by University of Sussex, EurekAlert!

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