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