Oak leaves harbor distinct microbial worlds on their opposite surfaces
A single leaf may look like a simple patch of green, but to the microscopic life that inhabits it, it is a vast landscape divided into different worlds.
Oak leaves conceal distinct microbial ecosystems on their opposing sides. Researchers at the Xishuangbanna Tropical Botanical Garden in China have discovered that the sun-drenched upper surface and the shaded, humid underside of a single oak leaf support fundamentally different bacterial habitats. These two sides exhibit striking seasonal differences in their microbial communities.
The upper surface, exposed to sunlight, ultraviolet radiation, and wind, selects for stress-tolerant bacteria. In contrast, the lower surface, with its higher humidity and presence of stomata, fosters sugar-fermenting and insect-associated bacteria. Though bacterial richness remained steady on both sides until late autumn, the upper surface later saw a surge in bacterial variety, while the lower surface experienced a decline in both diversity and abundance.
Interestingly, the abundance of key community members fluctuated early in the season before converging later. The lower-surface microbiomes were closely tied to the host plant's changing physiological traits, while the upper-surface communities seemed largely independent, instead being shaped by persistent environmental pressures.
This study underscores the importance of considering within-leaf heterogeneity in microbial ecology, as host plant characteristics determine how microbial communities respond to environmental changes.
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