THE EFFECT OF PHOSPHORUS ON THE FORMATION OF HYPHAE IN SOIL BY THEVESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGUS, GLOMUS FASCICULATUM

Abstract

Summary Hyphae formed in soil by the vesicular‐arbuscular (VA) mycorrhizal fungus, Glomusfasciculatum (Thaxter sensu Gerd.) Gerd. and Trappe were extracted using the membrane filter techniqe and their length was estimated by the grid intersection method. The effect of phosphorus on the formation of this external mycelium was assessed after sampling procedures had been investigated. Phosphorus supply was varied from amounts severely deficient to those adequate for the growth of subterranean clover. After 6 weeks, the alleviation of severe phosphorus deficiency increased both the length of infected root and the length of external hyphae per centimetre of infected root. Further additions of phosphorus decreased both of these measurements. However, the level of added phosphorus at which the most external hyphae was formed per centimetre of infected root was higher than the level of phosphorus which gave the greatest length of infected root. The increase in phosphorus supply which gave the greatest increase in the length of external hyphae per centimetre of infected root also decreased the formation of vesicles within infected roots. At phosphate levels adequate for growth of mycorrhizal plants, there was little development of either external hyphae in soil or vesicles within the mycorrhizal roots.

Plant growth and phosphorus uptake in mycorrhizal rangpur lime seedlings under different levels of phosphorus

“…The total EM increased with time and reached about 19 m g -1 in the substrate with +AMF plants at 90 DAT, in all P levels. These data are in agreement with previous works (Abbott et al, 1984;Schubert et al, 1987;Sylvia, 1988;Li et al, 1991), in which the total EM ranged from less than 1 to about 26 m g -1 .…”

“…Total EM and active EM always had higher figures in the substrate with +AMF plants, at all P levels, along the experiment. Although some authors (Abbott et al, 1984;Sylvia, 1988;Li et al, 1991) suggested the subtraction of the mycelium estimated in -AMF treatments from their respective +AMF counterparts, both data were presented, because it is quite difficult to distinguish mycorrhizal mycelium from that from other filamentous fungi (Sylvia, 1988;Kabir et al, 1996;. In addition, interactions between AMF and saprophytic fungi are unknown, whether stimulating or inhibiting each other.…”

“…A second evaluation was performed on the same sample, but under white light, in order to assess the total external mycelium. It is quite difficult to differentiate AMF hyphae from other filamentous fungi in the soil (Abbott et al, 1984), under microscope, unless they are attached to their spores and more accurate examinations are made. In addition, a mycorrhizal rizosphere is quantitatively and qualitatively different from a nonmycorrhizal one, with regard to soil microorganisms (Linderman, 1992).…”

“…The generally accepted hypothesis to explain this negative effect is the endophyte action, as C sink on the host (Graham et al, 1997;Jifon et al, 2002). Indeed, the relative development of the internal and the external mycelium should be in balance, to promote a positive growth response (Abbott et al, 1984).…”

Uptake of 109Cd by roots and hyphae of a Glomus mosseae/ Trifolium subterraneum mycorrhiza from soil amended with high and low concentrations of cadmium

“…Total and mycorrhizal root length was determined for RC and RHC by a line-intersect method (Tennant, 1975) after staining root subsamples in trypan blue (Kormanik & McGraw, 1982). Length of mycorrhizal hyphae was measured using a membrane filter-grid intersect method modified after Abbott, Robson & De Boer (1984). Modifications included the use of 2 ml aliquots and 20 mm diameter filter area.…”