Researchers Refute Long-Held Notion About Quinoa’s Unique “Water Balloons”

by Amir Hussein
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quinoa bladder cells research

Researchers at the University of Copenhagen have refuted a long-standing theory about the purpose of bladder cells in quinoa. Contrary to the previous belief that these cells contributed to the plant’s drought and salt resistance, it’s now understood that they actually provide protection against pests and diseases. This revelation could lead to the development of hardier quinoa varieties. The accompanying image shows these epidermal bladder cells under a microscope. Credit: University of Copenhagen.

For over a century, it was believed that the balloon-like structures on the surface of quinoa and similar plants, known as ‘bladders’, helped them endure dry and saline environments. However, this notion has been overturned by new findings from the University of Copenhagen.

In reality, these bladder cells fulfill a different yet crucial role. This discovery opens the possibility of breeding even more robust quinoa variants, potentially enhancing its global cultivation.

Under a microscope, these bladder cells resemble water balloons or glass art, a curiosity that has puzzled scientists for 127 years. Initially thought to aid in drought and salt tolerance, recent research has revealed an entirely different function for these structures.

A video demonstrates thrips attacking a quinoa plant lacking bladder cells, underscoring their protective role. Credit: University of Copenhagen.

This unexpected finding emerged from a recent study at the University of Copenhagen, which contradicted initial hypotheses. This new understanding may facilitate the expansion of this nutritious, climate-resilient crop.

“Quinoa’s reputation as a sustainable, protein-rich crop, adaptable to climate change, led scientists to believe its tolerance was due to the epidermal bladder cells on its surface. These cells were thought to store water and excess salt. However, our evidence refutes this,” explains Professor Michael Palmgren from the Department of Plant and Environmental Sciences.

A Defense Mechanism Against Pests

A study initiated three years ago by PhD student Max Moog and his supervisor Michael Palmgren aimed to explore the role of quinoa’s epidermal bladder cells in salt and drought resilience.

The team compared mutant plants, devoid of bladder cells, to wild quinoa plants, in terms of their response to salt and drought.

Surprisingly, bladder cells were found to have no beneficial effect on salt and drought tolerance. Instead, they act as barriers against pests and disease.

Photographs show the quinoa plant’s bladders (left) and a mutant variant without them (right), with blue arrows indicating thrips, a serious pest. Credit: University of Copenhagen.

“We observed that mutant plants without bladder cells excelled under saline and dry conditions, contrary to our expectations. However, they were more prone to insect infestations compared to those with bladder cells. This led us to realize the true function of these cells,” states Max Moog, now a postdoc and lead author of the study published in Current Biology.

The team discovered that bladder cells contain compounds repelling invaders, rather than the expected salt, even after adding extra salt to the plants.

“Bladder cells provide both a physical and chemical defense against pests. Insects find it difficult to access the plant’s tender green parts due to these cells. Additionally, the cells’ contents are toxic to these pests,” says Michael Palmgren.

The surface of many quinoa varieties is covered with these bladder cells, resembling tiny balloons on stems. Credit: University of Copenhagen.

The bladder cells, containing oxalic acid – a pest poison also found in rhubarb – also protect against common bacterial plant diseases like Pseudomonas syringae, likely by covering the leaf stomata, a common bacterial entry point.

“Our hypothesis is that these cells shield against other diseases, such as downy mildew, which significantly impacts quinoa yields,” adds Max Moog.

A Path to Enhanced ‘Super-Quinoa’

With numerous quinoa varieties, the bladder cell density varies, likely influencing their effectiveness as a defense mechanism.

Video of thrips attempting to attack a quinoa plant. Credit: University of Copenhagen.

“Varieties with more bladder cells are likely more pest and disease-resistant, though possibly less drought and salt-tolerant, and vice versa. These differences don’t alter quinoa’s inherent resilience to these conditions, but the explanation lies elsewhere than in the bladder cells,” explains Max Moog, highlighting:

“The newfound knowledge can assist in adapting quinoa to different regional conditions. In southern Europe, where dryness prevails, or in northern Europe, where pests are a greater issue than drought, selecting varieties based on bladder cell density would be strategic.”

Michael Palmgren suggests that this discovery offers a clear strategy for breeding ‘super-quinoa’ with enhanced pest and disease resistance, yet still resilient to salt and drought.

“These bladder cells, previously overlooked in breeding, could be the key to developing a super-quinoa through cross-breeding,” he states.

Michael Palmgren and Max Moog from the University of Copenhagen. Credit: University of Copenhagen.

This research adds a new layer to our understanding of quinoa, particularly in

Frequently Asked Questions (FAQs) about quinoa bladder cells research

What was the original belief about quinoa’s bladder cells?

It was previously believed that quinoa’s bladder cells helped the plant withstand drought and salty conditions.

What new discovery about quinoa’s bladder cells has been made by the University of Copenhagen researchers?

The researchers found that these bladder cells actually serve as a defense against pests and diseases, rather than aiding in drought and salt tolerance.

How does this discovery impact the future breeding of quinoa?

This finding paves the way for breeding stronger, more resilient quinoa varieties, as it offers new insights into the plant’s defense mechanisms.

What was the surprising revelation about bladder cells in mutant quinoa plants?

The study revealed that mutant plants without bladder cells performed well under salt and drought conditions, but were more susceptible to pest infestations, indicating a different function of the bladder cells.

What compounds are found inside quinoa’s bladder cells, and what is their purpose?

The bladder cells contain compounds like oxalic acid, which act as a physical and chemical barrier against pests and diseases.

How might this research influence the global cultivation of quinoa?

With the new understanding of bladder cells’ function, it’s likely that more resilient quinoa plants can be bred, potentially leading to wider cultivation and adaptation of this crop worldwide.

What is the potential for breeding ‘super-quinoa’ following this discovery?

The research suggests that breeding quinoa varieties with a high density of bladder cells could result in crops that are extra resistant to pests and diseases, while still being tolerant of salt and drought.

More about quinoa bladder cells research

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