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RELATIONSHIPS BETWEEN HOST AND ENDOPHYTE DEVELOPMENT IN MYCORRHIZAL SOYBEANS
Author(s) -
BETHLENFALVAY G. J.,
BROWN M. S.,
PACOVSKY R. S.
Publication year - 1982
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1982.tb04486.x
Subject(s) - mycelium , biology , endophyte , hypha , botany , host (biology) , fungus , nutrient , mycorrhiza , horticulture , biomass (ecology) , phosphorus , symbiosis , agronomy , bacteria , chemistry , ecology , genetics , organic chemistry
SUMMARY Symbiotic associations of soybeans and the vesicular–arbuscular mycorrhizal fungus Glomus fasciculatus were grown to maturity in a sand‐perlite rooting medium watered with a nutrient solution containing growth‐limiting amounts of soluble phosphorus. Development of fungal mycelia external and internal to the host plant's root system was measured by determining chitin in isolated fungal mycelium, in the rooting medium, and in the mycorrhizae. The biomasses of the extra‐ and intraradical mycelia were calculated from the values of chitin obtained spectrophotometrically. The amount of total fungal biomass relative to that of the host plant varied throughout the lifespan of the association and reached a maximum of 2.3 % 10 weeks after planting. The amount of intraradical mycelium increased throughout the host plant's life span. Extraradical fungal structures attained a maximum weight at the onset of logarithmic growth of the soybean pods and decreased thereafter. Cessation of the rapid growth phase of G. fasciculatus lagged behind that of the host plant's vegetative structures, but appeared to be related to pod development. The fungus to root dry wt ratio was 12–3% at senescence. The ratio of extra‐ to intraradical mycelium decreased throughout the association's lifespan. Since the extraradical hyphae are the organs responsible for enhanced nutrient uptake this ratio is proposed as an index of the endophyte's usefulness to the host. High values for this usefulness index coincided with significant growth enhancement of the host plant. Source–sink relationships in the host appear to be a determining factor in the growth of the fungal endophyte.