Decoding the chemistry of soil biotic interactions 🧪🌱

 Decoding the chemistry of soil biotic interactions 🧪🌱

🔀 Soil organisms play a critical role in soil formation and stability, being engaged in a fragile network of aboveground interactions.

🧱 The activity of specific groups of organisms can be observed and characterized over a vertical gradient in the rhizosphere:

1️⃣ PRIMARY (TAP) ROOT

🛠️ Function: anchorage, transport

🛡️ Defence against herbivores & pathogens: (↑) high

- Most insect herbivores occur in the top horizon of soils, interacting with taproots.

- Insects can be attracted or repelled by root secondary metabolites.

- Taproots are highly defended by chemicals against herbivores and pathogens.

2️⃣ LATERAL ROOTS

🛠️ Function: transport, uptake of nutrients & water

🛡️ Defence to herbivores & pathogens: (±) moderate

- Microbiome assembly is usually more deterministic (e.g., influenced by competition and predation).

- Plants grown on non-sibling exudates form more lateral roots compared with those grown close to autologous exudates (kin recognition).

3️⃣ FINE ROOTS

🛠️ Function: nutrient & water uptake

🛡️ Defence to herbivores: (↓) low/ defence to pathogens: (↑) high

- Plant pathogenic nematodes and microbes generally intrude from fine roots and are the most vulnerable organ.

- Wounded roots release chemicals that can attract pathogenic nematodes and fungi.

- Beneficial microbes, such as mycorrhizal fungi, rhizobia, and plant growth-promoting bacteria (PGPR), interact strongly with fine roots.

Image: overview of soil organisms and scope of interactions with root chemicals.