CO2 concentration and water availability alter the organic acid composition of root exudates in native Australian species

Abstract Purpose Root exudation of organic acids (OAs) facilitates plant P uptake from soil, playing a key role in rhizosphere nutrient availability. However, OA responses to CO 2 concentrations and water availability remain largely untested. Methods We examined the effects on exudates three Australian woodland species: Eucalyptus tereticornis , Hakea sericea Microlaena stipoides . Seedlings were grown glasshouse low exposed (400 ppm [aCO ] or 540 [eCO ]) treatments (100% holding capacity [high-watered] 25–50% [low-watered]). After six weeks, we collected OAs soil ( rhizo ) trap solutions which washed roots immersed exuded ). Results For E. changed composition, driven by increased malic acid plants eCO oxalic low-watered plants. H. had higher per (+ 116%) lower unit root mass (–77%) associated with larger but fewer cluster roots. M. 107%) 160%), while citric for : changes amounts composition positively under 2. Conclusion conclude that altered shifted exudates, modifying plant–soil interactions carbon economy.