Adaxial-abaxial leaf surface asymmetry is a key ecological driver of the phyllosphere microbiome.
Sugimoto H, Toyoda A, Furuta Y, Iwase T, Yaokawa R
Phyllosphere Microbiome
Every tree in your yard is running two completely different microbial ecosystems on a single leaf — one on the sunny upper side, one on the sheltered underside — and understanding which microbes live where could reshape how we think about leaf diseases and why some sprays work better than others.
The top and bottom of a leaf are surprisingly different worlds. Scientists sampled seven types of temperate trees over six months and found that the upper leaf surface (which gets more sun and dries out faster) hosts microbes specialized for surviving harsh, nutrient-poor conditions, while the underside (shadier, more humid, with pores that release gases and sugars) hosts microbes focused on growth and energy production. This means studying a whole leaf at once, as most researchers have done, blurs together two very distinct microbial stories.
Key Findings
Bacterial and fungal communities on the upper (adaxial) and lower (abaxial) leaf surfaces were consistently and compositionally distinct across all seven temperate tree species studied over six months.
The underside of leaves showed a higher proportion of negative (competitive) microbial interactions in co-occurrence networks compared to the upper surface, suggesting more intense ecological competition in that resource-rich zone.
Upper-surface microbes were enriched in nutrient-degradation pathways (consistent with a stressful, nutrient-poor habitat), while lower-surface microbes were enriched in biosynthesis and energy-generating functions (consistent with a resource-rich environment near stomata).
chevron_right Technical Summary
Scientists discovered that the top and bottom surfaces of leaves host distinctly different communities of bacteria and fungi, and that these differences are driven by the contrasting environments each surface provides — not just random chance. This challenges the common practice of studying leaves as a single uniform unit.
Abstract Preview
Microorganism-driven ecosystems on leaf surfaces play pivotal roles in regulating plant health and fitness. While individual leaves provide distinct microhabitats on their adaxial (upper) and abaxi...
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