Plants with wilting flowers aren't dying - they are saving energy

A wilting flower is not always a sign of poor health or inadequate care. It could actually be a strategic play, millions of years in the making, created by Mother Nature herself.

Researchers from Macquarie University, along with international collaborators, have discovered a simple strategy that has been overlooked: plants recycle resources from wilting flowers for future reproduction.

Recycling resources from wilting flowers

“Our research delivers the first direct demonstration that plants can salvage resources from wilting flowers and reuse these resources to promote future reproduction,” said lead author Honorary Professor Graham Pyke from Macquarie University.

Why bother with this recycling effort? Well, flowers aren’t just pretty faces. They are rich in energy and nutrients such as nitrogen and phosphorus. When they wilt, it isn’t necessarily the end but rather the beginning of another chapter.

Wilting flowers of Christmas bells

The focus of the three-year study was a native of Eastern Australia, the stunning Blandfordia grandiflora. Known commonly as Christmas bells, it casts a striking image with its vibrant red and yellow flowers, especially around December.

“Our research takes place on a plantation containing several hectares of native wet heath where Christmas bells flower quite profusely, along with a commercial shadehouse,” noted Professor Pyke.

To assess the abilities of the plant, the team used an array of techniques. They modulated pollination and flower wilting and then gauged the effect on seed production and reflowering.

Storing up chemical energy

The researchers soon realized things weren’t exactly as they had predicted. They found that plants did not use resources from wilted flowers to bolster short-term reproduction.

“These plants salvage resources invested in reproduction during one flowering season and reuse these resources during the next flowering season,” explained Professor Pyke.

Blandfordia grandiflora was found to transfer resources from its wilting flowers to its underground corms and roots, effectively storing this “chemical energy” to produce new flowering stems in the subsequent season, often a year later.

Resource management in wilting flowers

Professor Pyke noted that plants work on principles similar to economics. “Plants must make decisions about where to allocate their limited resources; investing in one area means they can’t invest as much in another.”

This concept of resource allocation prompted Professor Pyke to investigate flower wilting, which he anticipated to be a plant’s mechanism of diverting resources to other processes.

The results, however, were not quite what he expected. The plants were storing their reclaimed resources for the next flowering season – not using them right away.

According to Professor Pyke, plants have different ways of managing their flowers post reproduction, with wilting being just one of many strategies. Some plants, such as the jacaranda and the frangipani, even shed their flowers before they wilt.

Seed production and wilting in flowers

The study findings were confirmed through various experiments. One such experiment compared seed production between plants with flowers that were allowed to wilt and those with petals removed to prevent wilting.

Another experiment stopped seed production in all flowers but allowed wilting in one group of plants. Results showed that plants with wilting flowers were more likely to reflower the next season than those where wilting was prevented.

Factors that influence seed production

The study also took into consideration other factors that might influence seed production, such as stem height, the number of flowers per stem, and flower position.

“Taller flowering stems, for example, produced more seeds and heavier seeds, as did stems with more flowers. But flowers positioned lower down on the plant tended to have fewer seeds, and seeds that weighed less,” said Professor Pyke.

“Our findings pave the way for further research into other plant species, and how they recover and reuse the resources from wilting flowers.”

An exciting road lies ahead, with a lot to discover. Future research will explore what these salvaged resources are composed of, how plants move and change them, and whether saving these resources outweighs the costs of making flowers in the first place.

The study is published in the journal Plant Biology.

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