Effects of drought on host and endophyte development in mycorrhizal soybeans in relation to water use and phosphate uptake

Abstract

1988. Effects of drought on host and endophyte development in mycorrhizal soybeans in relation to water use and phosphate uptake. -Physiol. Plant. 72: 565-571. Soybean [Glycine max (L.) Merr.] plants were grown in pot cultures and inoculated with the vesicular-arbuscular mycorrhizal (VAM) fungus GIomus mosseae (Nicol. & Gerd.) Gerd. and Trappe or provided with P fertilizer (non-VAM plants). After an initial growth period (21 days), plants were exposed to cycles of severe, moderate or no drought stress over a subsequent 28-day period by rewatering at soil water potentials of -1.0, -0.3 or -0.05 MPa. Dry weights of VAM plants were greater at severe stress and smaller at no stress than those of non-VAM plants. Phosphorus fertilization was applied to produce VAM and non-VAM plants of the same size at moderate stress. Root and leaf P concentrations were higher in non-VAM plants at all stress levels. All plants were stressed to permanent wilting prior to harvest. VAM plants had lower soil moisture content at harvest than non-VAM plants. Colonization of roots by G. mosseae did not vary with stress, but the biomass and length of the extraradical mycelium was greater in severely stressed than in non-stressed plants. Growth enhancement of VAM plants relative to P-fertilized non-VAM plants under severe stress was attributed to increased uptake of water as well as to more efficient P uptake. The ability of VAM plants to deplete soil water to a greater extent than non-VAM plants suggests lower permanent wilting potentials for the former.

Water uptake by safflower and wheat roots infected with arbuscular mycorrhizal fungi

“…These mycorrhizal fungi also did not affect the total amount of soil water extracted before safflower and wheat plants wilted completely, even though soil hydraulic conductivity was probably very low under these dry soil conditions (c. 10"' cm d"' or less at 'F^ < -0-5 MPa (predicted as in van Genuchten, 1980). By contrast, Bethlenfalvay et al (1988) found fhat M soybean plants depleted soil water to a greater extent than NM soybean, and Hardie & Leyton (1981) found similar results in clover. In both studies, however, M plants were more intensely rooted and might have simply explored a greater soil volume than NM plants, whereas in the present study, mycorrhizal infection did not affect L^.…”

Effectiveness of arbuscular mycorrhizal fungi in the protection of olive plants against oxidative stress induced by drought

“…Such growth response to mycorrhizal colonization was previously observed in other olive variety (Rougemont, 2007) and many other plant species such as Citrus tangerine , Poncirus trifoliate (Wu et al, 2008), date palm Faghire et al, 2010), pistachio (Abbaspour et al, 2012) and carob . The positive effect on plant growth has been attributed to the improvement of water and nutrients uptake due to the greater absorption of the surface area provided by extensive fungal hyphae and the increased root length and density (Bethlenfalvay et al, 1988;Faber et al, 1991;Fouad et al, 2012Fouad et al, , 2013Essahibi et al, 2013). In previous study we showed enhanced water uptake and nutrients (potassium and phosphorus) accumulation in mycorrhizal olive plants compared to NMplants both under well watered and water def icit conditions (Fouad et al, 2013).…”

Arbuscular mycorrhizae and soil/plant water relations

“…Correlative evidence has linked soil aggregation with increased drought resistance (Davies et al 1992). Physiologically, mycorrhizae-mediated uptake of bound soil water may be analogous to the uptake of phosphorus, where tapping supplies not available to the nonAM plant results in a positive growth response (Bethlenfalvay and Schüepp 1994).…”

“…The findings support the assertion that external, soil hyphae may play an important role in mycorrhizal influence on the water relations of host plants. Bethlenfalvay and colleagues had suggested earlier that, theoretically, colonization of soil by hyphae might be expected to have as great (or greater) influence on host behavior during drought as colonization of roots (e.g., Bethlenfalvay and Linderman 1992). Others recently reported that, among six AM species tested, effectiveness in enhancing plant water uptake from soil appeared related to the amount of external mycelium produced by each AM fungus as well as to the frequency of root colonization in terms of live and active fungal structures (Marulanda et al 2003).…”