Let the sun shine and the plants will follow

Leonardo da Vinci, the Italian Renaissance scientist and artist extraordinaire, in the 15th century was the first to record his observation that some plants appeared to follow the Sun, and he was not the last. How this was scientifically achieved and why this occurred, however, remained a mystery to him and everyone that followed. But a European team of researchers may have come one step closer to solving this mystery. The answer, they say, lies with auxin - a class of plant hormone. The findings of their study were published in the journal Nature.

While the question as to why plants always seem to turn towards the light or climb upwards instead of down seems simple enough, the answer is not. Researchers have long theorised that the culprit behind this phenomenon is auxin, a class of plant hormone, which intrigued even Charles Darwin in the 19th century. Scientists, however, have been unable to gain a complete understanding of how it worked... until now.

New research conducted by scientists Department of Plant Systems Biology at the Vrije Universiteit Brussel (VIB) and at the University of Ghent in Belgium at shows an important new link in the transmission of auxin through the plant. The researchers have identified that auxin is stored at specific sites.

Led by Elke Barbez, under the supervision of Jürgen Kleine-Vehn from VIB and Jirí Friml, also from VIB and the University of Ghent, the team determined that the transport of auxin through the plant plays a vital, though complex, role. Auxin is initially produced in growing sections of the plant before it is sent to other parts where it is needed, including the stem. In order for the plant to best absorb the Sun's rays efficiently, the stem needs to straighten out as soon as possible. What happens then is that more auxin will be delivered to the underside of the stem than to the topside, resulting in the underside growing faster and the stem straightening out. By regulating where auxin is transported, plants are able to take optimal advantage of local and changing conditions.

According to the researchers, their findings will have far-reaching impact and may also benefit agricultural scientists and farmers. Increasing our knowledge of auxin may give farmers the means to grow crops more efficiently. For example, increasing the auxin levels at just the right moment and in the right place would result in better growth and greater yields, the team says.

Besides securing support from VIB and the University of Ghent, this research was jointly financed by the Vienna Science and Technology Fund (WWTF) in Austria, the Agency for Innovation by Science and Technology (IWT) in Belgium, the Odysseus program of the Research Foundation-Flanders in Belgium, the Swiss National Funds, and the Ministry of Education, Youth and Sports of the Czech Republic.