The Leeds team proved the presence of the offset by using a clinostat, which slowly rotates a plant growing on its side, thereby withdrawing a stable gravity reference and enabling the researchers to monitor the anti-gravitropic offset mechanism working unopposed by a coordinated gravitropic response. Under these conditions they observed that shoot and root branches displayed an outward bending growth, away from the main root and shoot that would normally be masked by the interaction with gravity-sensitive growth.
Dr Kepinski said: "The angle of growth of branches is an exceptionally important adaptation because it determines the plant's capacity to capture resource above and below ground. Depending on what sort of soil a plant is in, it might be beneficial to be foraging for nutrients in the top soil or to be going deeper. Similarly, in the shoot, a plant might gain an advantage from having more steeply pitched branches to avoid shading from neighbouring plants. Until now, nobody really knew how non-vertical growth angles, referenced to gravity like this, were set and maintained."
He added: "These insights are important for breeding and biotechnological approaches to crop improvement because breeders and seed companies want to be able to alter plant architecture to optimise the performance of crops. For example, lateral root growth angle has been shown to be critical for increasing nutrient uptake in both broadleaf and cereal crop species. Our findings provide tools and approaches to help meet these crop improvement challenges."
The team used the flowering plant Arabidopsis thaliana (thale cress), as well as pea, bean and rice plants in their experiments, observing the same results.
Kepinski expects the same mechanism to be observed in larger plants and young tree seedlings. In older trees, the mechanisms driving gravity sensitive growth in woody tissues are different to those in non-
|Contact: Chris Bunting|
University of Leeds