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- Title
Herbivory enhances legume-rhizobia symbioses function, increasing aboveground allocation of biologically fixed nitrogen, but only in soils without additional nitrate.
- Authors
Thompson, Morgan N.; Lamp, William O.
- Abstract
Purpose: Beneficial soil microbes, such as rhizobia, engage in facultative symbioses in the roots of leguminous host plants to exchange nitrogen for products of photosynthesis, and these symbioses can be altered by biotic and abiotic factors. Here, we investigated how soil nitrate supply and aboveground insect herbivory interact to influence biological nitrogen fixation in Medicago sativa (alfalfa or lucerne). Methods: Using field and greenhouse experiments, we quantified above- and belowground allocation of rhizobially fixed nitrogen using isotopic nitrogen ratios in plants with different combinations of herbivory and nitrate supplementation. We caged Empoasca fabae (potato leafhopper) on fixing and non-fixing cultivars of M. sativa and supplemented soils with varied nitrate concentrations. Results: We detected strong changes in legume above- and belowground allocation of fixed nitrogen in response to both herbivory and nitrate supply. Moderate nitrate soils, irrespective of herbivory, induced little to no fixed nitrogen allocation across both field and greenhouse experiments. In the field only, non-supplemented soil increased aboveground allocation of fixed nitrogen following herbivore damage but resulted in no changes belowground. In contrast, non-supplemented and high nitrate soils in the greenhouse increased above- and belowground fixed nitrogen allocation relative to moderate nitrate soils. Conclusion: Our results demonstrate herbivory drives distinct plant allocation strategies across soil nitrate levels, advancing our understanding of how rhizobia influence legumes both above- and belowground. Herbivory-induced changes in rhizobia-legume symbioses are likely widespread across both agricultural and natural ecosystems.
- Subjects
LEGUMES; NITROGEN fixation; SYMBIOSIS; NITRATES; ALFALFA; SOILS
- Publication
Plant & Soil, 2021, Vol 465, Issue 1/2, p301
- ISSN
0032-079X
- Publication type
Article
- DOI
10.1007/s11104-021-04999-6