Leaf growth, root formation, and reproduction – Look to hormones for the answer

Plants cannot outrun drought, flooding, or hungry herbivores. And yet, they survive, thrive, and reproduce. Their secret? A finely tuned survival strategy – phytohormones. “The adaptability of plants fascinates me. They develop mechanisms to spread and ensure the next generation,” says Ondřej Novák, head of the Laboratory of Growth Regulators. Together with his team, he has mastered the art of detecting even the tiniest concentrations of plant hormones – making them world leaders in the field. This article was first published in A / Magazine, the official quarterly of the Czech Academy of Sciences.

An old local legend from the medieval Buchlov Castle in the Czech Republic tells of a young squire, wrongfully sentenced to death for poaching. To prove his innocence, he uprooted a linden sapling and replanted it upside down. “If this tree turns green within a year and a day, you will know you have condemned an innocent man,” he declared to the gathered judges. They decided to wait and, sure enough, the tree flourished. The young man was granted his freedom.

Buchlov’s “tree of innocence” remains a highlight of the castle tour, reminding visitors not only of one youngster’s ingenuity but, more importantly, of the extraordinary resilience and vitality of plants.

“Their adaptability truly fascinates me. They cannot move from their spot, yet they respond remarkably well to changing conditions. They are capable of developing mechanisms to survive, proliferate, and ensure the next generation,” says bioanalyst Ondřej Novák, head of the Laboratory of Growth Regulators, a joint facility of the Faculty of Science at Palacký University Olomouc and the Institute of Experimental Botany of the Czech Academy of Sciences (CAS).

Ondřej Novák, head of the Laboratory of Growth Regulators. (CC)

The chemical cocktail of plants
Research-wise, Novák is particularly interested in plant hormones – specifically, phytohormones. They function as messengers, transmitting signals from one part of the organism to another. Like animal hormones, including those in humans, they alert the plant to environmental changes and warn of danger. Consider adrenaline, for instance, which is produced by the adrenal glands and triggers the fight-or-flight response.

“From a chemical perspective, phytohormones are small molecules that exert a strong effect on plants even at extremely low concentrations. They are synthesized in specific tissues, bind to receptors, and trigger a cascade of reactions at the cellular, organ, and holistic levels,” Novák explains.

Scientists classify phytohormones into at least eight primary groups, along with several secondary ones. The main categories include auxins, cytokinins, gibberellins, brassinosteroids, strigolactones, abscisic acid, jasmonates, and ethylene. Each group has a distinct chemical structure and functions, with some responding to stress and others regulating root formation, leaf growth, flowering, seed development and ripening, or seed detachment from the parent plant. In short, it can be said phytohormones oversee nearly all key phases of plant growth and development. Their roles are broad, and a single hormone can influence multiple processes – some phytohormone groups work together, while others counteract each other.

The king of hormones: auxin
The first plant hormone identified and described by researchers in the early 20th century was auxin. With a bit of hyperbole, auxin could be called the “universal developmental signal” in the plant world due to its vast range of effects. Textbooks on plant physiology list an array of processes this plant hormone influences: phototropism (bending toward light), shoot formation, root initiation, vascular tissue regeneration, leaf senescence, and fruit ripening. In fact, it’s easier to list what auxin does not regulate.

Its impact is so astonishing even experts remain amazed. “The universal importance of auxin has, in some ways, been its curse. For decades, nobody could explain or even imagine how such a simple compound could have so many seemingly unrelated and often contradictory effects,” wrote Jiří Friml, one of our leading auxin researchers, in the Czech popular science journal Živa. (Friml is based at the Institute of Science and Technology Austria).

The plant hormone auxin influences phototropism (bending toward light), root initiation, fruit ripening, and an array of other processes.

The Czech Republic has a deep tradition of plant hormone research, particularly on auxin. The Institute of Experimental Botany of the CAS, where Novák works, has long been a leader in this field. Current CAS President [as of 5 March 2025], Eva Zažímalová, has also dedicated her career to auxin research.

“Phytohormone research in the Czech Republic is exceptionally strong – far stronger than in neighboring countries of comparable size. I fully realized this during my postdoc studies in Sweden. We focus on phytohormones both at the CAS headquarters in Prague and here in Olomouc,” Novák notes.

Measuring the immeasurable
Initially, Novák was reluctant to leave for his postdoc abroad. He had a promising research project underway in Olomouc and played the viola in a cimbalom band in his hometown of Přerov. It wasn’t until four years after completing his PhD that he finally made the move – and in hindsight, he has zero regrets. “Looking back, it was one of the best decisions of my life. I strongly encourage all students and early-career scientists to go abroad,” says the bioanalyst, who rejoined his band after returning home.

Now leading the Laboratory of Growth Regulators in Olomouc, Novák strives to maintain an international research environment. However, he is frustrated that he cannot offer his team salaries comparable to those in developed countries. “We can’t compete with Swedish salaries, but recently we have been successful in securing grants,” Novák says. “We’ve built a beautiful new science campus for students, won several Czech Science Foundation grants, and are involved in the Jan Amos Komenský (Johannes Amos Comenius) Operational Programme as well as two major EU projects that are part of Horizon Europe.”

The research facility in Olomouc offers students and scientists a unique research focus: developing highly sensitive methods and innovative techniques to detect, identify, and measure even the tiniest concentrations of plant hormones. In this field, they really are world leaders – evidenced by Novák’s repeated ranking in Clarivate Analytics’ Highly Cited Researchers list, a database of the top 1% of most-cited scientists in their respective fields.

Researchers at the Laboratory of Growth Regulators are currently capable of quantifying more than a hundred phytohormones from minuscule sample sizes. While standard methods measure hormone concentrations at 10^-12 to 10^-15 moles per gram of fresh weight (picomolar to femtomolar concentrations), the Olomouc team operates at attomolar levels (10^-18 moles, SI symbol: amol).

Ondřej Novák's team adapts methods for measuring hormones that aren’t typically used in plant physiology.

The Olomouc lab can detect phytohormones not just at the tissue level but even within individual cells and isolated intracellular structures – organelles. “We are a leading laboratory in this field. We set the direction for how hormone measurements are conducted. Our uniqueness lies in adapting methods that aren’t typically used in plant physiology,” Novák explains. To refine hormone detection, the researchers experiment with techniques from medicine, food science, and proteomics – the large-scale study of proteins and their properties.

The foundation of phytohormone measurements in the Olomouc lab is mass spectrometry, which functions on the basis of determining the mass of individual charged particles (ions). To be able to analyze the molecules of interest, plant chemists must first remove thousands of interfering compounds from their samples. “For instance, we might be interested in just fifty low-molecular-weight organic compounds, yet at the start of the process, a plant leaf might contain ten thousand such compounds. To separate the unnecessary ones, we use various isolation techniques and then combine liquid chromatography with mass spectrometry,” Novák describes.

Finding the hormone
Picture a green leaf. Researchers weigh it, freeze it in liquid nitrogen, and grind it into a fine powder. The sample is mixed with an extraction agent – such as 10% methanol with a hint of formic acid – and left to extract before being spun in a centrifuge, which separates solids from liquids. This step removes plant tissue debris, leaving a solution still teeming with unwanted compounds – pigments, sugars, and proteins.

A plant sample mixed with an extraction agent.

Specialized filters with variously sized sorbents are used to trap these contaminants (an isolation technique continuously refined at the Olomouc lab with ever-smaller filters and more selective sorbents). The final purified solution is enriched with the target molecules and then analyzed via mass spectrometry.

“Our methods are incredibly fast, extremely sensitive, and reliable even with miniscule plant samples weighing mere milligrams – or even less. In each sample, we can simultaneously measure a hundred compounds, nearly twice as many as previous techniques allowed,” Novák adds. His team continues to refine this methodology in cooperation with the Swedish University of Agricultural Sciences in Umeå – the very place he once hesitated to go. Clearly, though, the move paid off.

While Novák is pleased to see his name among the world’s most-cited scientists in his field, he takes even greater pride in seeing “his” methods widely adopted and actively used. “I know colleagues in Cambridge and Madrid who use our protocols, adapting them to their own lab conditions,” the bioanalyst says. Yet he refuses to rest on his laurels.

“Bioanalytical techniques evolve rapidly, and artificial intelligence will undoubtedly play a role in shaping their future. That’s why it is crucial to stay attuned to advancements not only in plant science but also in medicine and beyond. Science involves a great deal of luck – but you can help luck along by keeping an open mind regarding new ideas and perspectives,” Novák concludes.

The article first came out in the 3/2024 Czech issue of A / Magazine:

3/2024 (version for browsing)
3/2024 (version for download)

Ondřej Novák is one of the scientists involved in the STARMORPH project, which investigates the role of auxin in plant growth and morphogenesis. Last year, the project was awarded an ERC Synergy Grant from the European Research Council, securing €10 million in funding.

Written by: Leona Matušková, External Relations Division, CAO of the CAS
Translated and prepared by: Tereza Novická, External Relations Division, CAO of the CAS
Photo: Jana Plavec, External Relations Division, CAO of the CAS; Ota Blahoušek, Institute of Experimental Botany of the CAS

 The text and all photos are released for use under the Creative Commons licence.

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