Vascular plants produce an entire series of different small signalling molecules, so-called phytohormones, which regulate growth and differentiation processes. Auxins, one of the best-known plant growth factors, have an extremely wide spectrum of activity, and are particularly important. They play a decisive role in almost all plant growth processes, including the shade avoidance reaction. To date, the underlying mechanism was however not fully comprehended. Prof. Pollmann stated that it had been known that the effect of auxin is based on an interaction of auxin formation, transportation and signal transduction. These processes are all influenced by a low red to far-red ratio, but the exact mechanisms were not understood.
Protein distribution ensures directional the flow of hormones
A group of research scientists working under the auspices of the ecophysiologist Dr. Ronald Pierik at the Utrecht University (NL) has now managed to shed light on the matter and further clarify the growth processes in the shoots during the shade avoidance syndrome. They made an interesting observation, namely that shoot growth during a low red to far-red ratio is subject to an intact auxin perception mechanism and is dependent on the accumulation of auxin in the shoot. The auxin transport protein PIN-FORMED 3 (PIN3) is primarily responsible for this accumulation. The formation of PIN3 is enhanced when the ratio between red to far red is low. It primarily accumulates in the lateral endodermal cell walls. This distribution of PIN3 leads to an auxin flow towards the epidermal cell layers, which are responsible for the elongation growth of the shoot.
Comparison between plants in light and shade
This working hypothesis could be experimentally verified by collaboration with Prof. Stephan Pollmann, an expert for phytohormones at the Ruhr University in Bochum. Using state-of-the art mass spec
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