The effect of temperature and available phosphorus on the growth of ectomycorrhizal Sitka spruce

• Main Author: McKay, Helen Mary
• Published: University of Edinburgh 1979
• Subjects: 634.9
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.666285

The response of Sitka spruce seedlings to inoculation with mycorrhizal fungi was studied over a range of root temperatures and available phosphorus. Fungi were isolated from roots of plantation Sitka spruce by surface sterilizing for short periods with dilute mercuric chloride. Four Basidiomycete isolates were selected in preliminary synthesis experiments. Multiple-seedling growth modules were constructed in which sterile conditions could be maintained, a specified nutrient regime could be imposed for up to 5 months and root temperature could be controlled independently of shoot temperature. Seedlings, with one of five fungal treatments, were grown at ten root temperatures from 3 to 35 °C. The isolates were capable of forming mycorrhizae but differed in their tolerance of high temperatures. All formed mycorrhizae at low temperatures. Average root length increased with temperature throughout the range but above 24°C total root length decreased. The number and length of mycorrhizal roots formed by three isolates was determined by the general effect of temperature on root growth but the infection rate of the fourth was positively related to temperature. This isolate stimulated root production at low temperatures. Growth of the four isolates in buffered pure culture media was broadly similar to their performance in association with the higher plant. Inoculation did not influence the distribution of nitrogen, phosphorus or potassium within phosphorus deficient seedlings. The degree of infection by the four isolates increased with available phosphorus from .002 to 10 mg./l. The benefits of the four isolates were influenced by phosphorus supply. It is suggested that host performance is related to root number and length irrespective of mycorrhizal status and where mycorrhizae are formed performance is related to the formation of mycelial strands and to a lesser extent the efficiency of uptake and use of absorbed phosphorus.