Abstract Title

Nutrient Availability and Germination Status Affect Plant-Microbe Interactions in Fern Gametophytes

Disciplines

Integrative Biology | Plant Biology

Abstract

Symbiotic plant-microbe interactions involving nutrient exchange exist in seed plants, but evidence for similar functional relationships in gametophytes of non-seed plants are limited. Here, an N-fixing bacterium was added to chemically defined, liquid media cultures containing haploid ferns at two stages of development. Plants were assessed phenotypically by photomicroscopy and chemically for C and N content by elemental analysis. The highest C:N occurred in control media lacking C and bacteria. All other treatments had a higher measured N content, contributing to a lower C:N. Media with glucose promoted mixotrophic behavior (use of both CO2 and C4 glucose) in gametophytes, evident as a heavier C isotope signature in plant tissue dry mass. Increased plant C uptake allowed for an increased N uptake such that C:N decreased. The lowest C:N and highest %N were found in glucose treatments inoculated before fern spore germination. However, the most vigorous plant phenotypes were found in cultures inoculated after spore germination. The co-culture of plants with the bacterium had beneficial effects on plants, except when bacteria had early access to free glucose in the resource environment.

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Nutrient Availability and Germination Status Affect Plant-Microbe Interactions in Fern Gametophytes

Symbiotic plant-microbe interactions involving nutrient exchange exist in seed plants, but evidence for similar functional relationships in gametophytes of non-seed plants are limited. Here, an N-fixing bacterium was added to chemically defined, liquid media cultures containing haploid ferns at two stages of development. Plants were assessed phenotypically by photomicroscopy and chemically for C and N content by elemental analysis. The highest C:N occurred in control media lacking C and bacteria. All other treatments had a higher measured N content, contributing to a lower C:N. Media with glucose promoted mixotrophic behavior (use of both CO2 and C4 glucose) in gametophytes, evident as a heavier C isotope signature in plant tissue dry mass. Increased plant C uptake allowed for an increased N uptake such that C:N decreased. The lowest C:N and highest %N were found in glucose treatments inoculated before fern spore germination. However, the most vigorous plant phenotypes were found in cultures inoculated after spore germination. The co-culture of plants with the bacterium had beneficial effects on plants, except when bacteria had early access to free glucose in the resource environment.