Our recently completed multi-year project suggests that there is no straight answer to this question! We sampled the leaves of different rice varieties across 3 years, finding that bacterial communities that live inside vs. on the surface of leaves differ in many ways, and over time. As expected from greater exposure to environmental influences (including dispersing bacteria), the microbiota on leaf surfaces is typically more variable, more rich, and more unstable. Despite these differences, however, largely the same bacterial genera colonized both leaf niches, including our favourite Methylobacterium. Finally, we find that community composition and load changes as the plant matures. So, while the answers are complex, there are some patterns to the madness, and the next question is to figure out whether and how these patterns matter to the host plant. Find out more in our paper, and enjoy this beautiful SEM image of the surface of a rice leaf (credit: Pratibha Sanjenbam and Santhosh Kumar).
AdaptationLab 