Arbuscular mycorrhizas are beneficial under both deficient and toxic soil zinc conditions
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Background and aims
Arbuscular mycorrhizas (AM) play different roles in plant Zn nutrition depending on whether the soil is Zn-deficient (AM enhancement of plant Zn uptake) or Zn-toxic (AM protection of plant from excessive Zn uptake). In addition, soil P concentration modifies the response of AM to soil Zn conditions. We undertook a glasshouse experiment to study the interactive effects of P and Zn on AM colonisation, plant growth and nutrition, focusing on the two extremes of soil Zn concentration—deficient and toxic.
We used a mycorrhiza-defective tomato (Solanum lycopersicum) genotype (rmc) and compared it to its wild-type counterpart (76R). Plants were grown in pots amended with five soil P addition treatments, and two soil Zn addition treatments.
The mycorrhizal genotype generally thrived better than the non-mycorrhizal genotype, in terms of biomass and tissue P and Zn concentrations. This was especially true under low soil Zn and P conditions, however there was evidence of the ‘protective effect’ of mycorrhizas when soil was Zn-contaminated. Above- and below-ground allocation of biomass, P and Zn were significantly affected by AM colonisation, and toxic soil Zn conditions.
The relationship between soil Zn and soil P was highly interactive, and heavily influenced AM colonisation, plant growth, and plant nutrition.
KeywordsArbuscular mycorrhizas (AM) Zinc Phosphorus Mycorrhiza defective tomato mutant (rmc) Solanum lycopersicum (Tomato)
The authors wish to thank Dr Michael Rose and other members of the ‘Cav-Lab’ for valuable discussions. We also gratefully acknowledge Dr Susan Barker and Prof. Sally Smith for continued access to the rmc and 76R genotypes of tomato. This research was in part funded by the Monash University, School of Biological Sciences. TRC also wishes to acknowledge the Australian Research Council and the Monash Research Accelerator program for financial support.
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