Photosynthetic Sucrose Drives Lateral Root Growth in Arabidopsis Thaliana
Key Highlights :
Plant growth is driven by light and supplied with energy through photosynthesis by green leaves. It is the same for roots that grow in the dark—they receive the products of photosynthesis, in particular sucrose (sugar), via the central transportation pathways of phloem. In their study published in Current Biology, Dr. Stefan Kircher and Prof. Dr. Peter Schopfer from the University of Freiburg's Faculty of Biology have now shown in experiments using the model plant Arabidopsis thaliana (thale cress) that the sucrose not only guarantees the supply of carbohydrates to the roots, it also acts as a signal transmitter for the formation of light-dependent root architecture.
The experiments conducted by Kircher and Schopfer showed that the sucrose produced through photosynthesis is the decisive signal transmitter. They placed the plants in a room with light but with no carbon dioxide (CO2) in the air, thus making photosynthesis impossible. The outcome was that no more lateral roots were formed. This result was confirmed by another experiment in which the two biologists treated either the leaves or the roots in the dark with a solution of sucrose. In both approaches, lateral roots developed the same as in control plants that were exposed to light.
The sucrose that is transported to the tip of the root then regulates the production of the plant hormone auxin. This hormone drives the rate of formation of new lateral roots, which—along with elongation of the primary root—is synchronized by the joint signal transmitter. Administering tryptophan to the roots at the same time as treating the leaves with sucrose had the greatest effect. By contrast, tryptophan had little effect if it was applied to the leaves or without sucrose at the roots.
These results show that the production of sucrose in leaves is necessary for the formation of lateral roots. It confirms the hypothesis that sucrose acts as a signal transmitter for light stimuli, enabling the root growth to adapt to the current photosynthesis performance of the leaves as light and other environmental conditions change. The sucrose produced through photosynthesis serves as a trigger for the synthesis of auxin, which drives the rate of development of new lateral roots.
In conclusion, the study conducted by Kircher and Schopfer has shown that photosynthetic sucrose is a key factor in driving lateral root growth in Arabidopsis thaliana. This process is regulated by the joint signal transmitter of sucrose and auxin, and it enables the root growth to adapt to changing photosynthesis performance of the leaves. The research conducted by these two biologists not only sheds light on the process of lateral root growth, but also provides insight into the complex relationship between light, sucrose, and auxin in plants.
