Lecture 4 - Beneficial Soil Biology

ACC deaminase

microbial enzyme that breaks down ACC = precursor of plant stress hormone ethylene

Arbuscule

fungal structure inside a root cell = site of nutrient exchange between plant / fungus

Associative

Nitrogen Fixation occurring on the root surface (as opposed to symbiotic)

Endophytic

bacteria or fungus that lives inside the plant tissue without causing disease, often providing benefits such as increased nutrient absorption or stress resistance.

Extraradical

outside the root system – mycorrhizal hyphae that proliferate in the soil and interact with soil nutrients.

Flavonoid

chemicals secreted by plant root systems that attract rhizobial bacteria to the root surface for nitrogen fixation.

Glomalin

glycoprotein secreted by mycorrhizae that stabilises soil structure and enhances soil carbon sequestration.

Hyphae

filamentous threads of mycorrhizal fungal cells that extend into the soil, facilitating water and nutrient absorption for plants.

nod factors

chemicals (lipochitooligosaccharides) produced by rhizobia involved in nodulation and the establishment of symbiotic relationships with leguminous plants, leading to root nodule formation and nitrogen fixation.

Nodulation

outcome of successful legume/rhizobial communication allowing BNF in root nodule

Rhizosphere

soil immediately next to & influenced by the root system

Strigolactone

phytohormone stimulating mycorrhizal spore germination (prevents shoot branching) and enhancing nutrient uptake in plants.

Symbiotic

relationship that both partners benefit from – C cost but nutrient benefit to the plant relationships, such as those between legumes and rhizobia, where both organisms provide mutual advantages.

Take-All

soilborne fungal disease of wheat that decreases yield and is caused by the pathogen Gaeumannomyces graminis.