Phosphorus-32 absorption and translocation to host plants by arbuscular mycorrhizal fungi at low root-zone temperature

Abstract

Arbuscular mycorrhizal (AM) mycelia persist in soil over winter. Functioning of the AM symbiosis very early in the spring when the soil temperature is low may be of ecological significance for perennial and biannual plants in cool climates. An indoor experiment was conducted to investigate the effects of low root-zone temperatures on ³²P uptake by 10-week-old leek plants (Allium porrum L.) inoculated or not with the AM fungus Glomus intraradices Schenck & Smith. Plants were grown in a greenhouse at approximately 23°C prior to exposing their roots to 23°C, 15°C or 0°C. Mycorrhizal colonization increased ³²P activity of leek leaves at a root-zone temperature of 23°C seven days after injection of ³²P into the soil, whereas 14 days after injection, ³²P increases were measured at both 23°C and 15°C. The lack of difference in ³²P activity between AM and non-AM plants at 0°C, both 7 and 14 days after injection, suggests that the AM fungus is not functional at this low root-zone temperature.