Effects of ectomycorrhizal and vesicular-arbuscular mycorrhizal fungi on drought tolerance of four leguminous woody seedlings

Abstract

Seedlings of Acacia auriculiformis A. Cunn. ex. Benth., Albizia lebbeck (L.) Benth., Gliricidia sepium (Jac.) Walp and Leucaena leucocephala (Lam.) de Wit. were inoculated with an ectomycorrhizal (Boletus suillus (L. ex. Ft.) or indigenous vesicular-arbuscular mycorrhizal (VAM) fungi in a low P soil.The plants were subjected to unstressed (well-watered) and drought-stressed (water-stressed) conditions. In Gliricidia and Leucaena, both mycorrhizal inoculations stimulated greater plant growth, P and N uptake compared to their non-mycorrhizal (NM) plants under both watering regimes. However, in Acacia and AIbizia, these parameters were only stimulated by either ectomycorrhiza (Acacia) or VA mycorrhiza (Albizia). Growth reduction occurred as a result of inoculation with the other type of mycorrhiza. This was attributed to competition for carbon between Acacia and VA mycorrhizas and parasitic association between Albizia and ectomycorrhiza.Drought-stressed mycorrhizal and NM Leucaena, and drought-stressed mycorrhizal Acacia tolerated lower xylem pressure potentials and larger water losses than the drought-stressed mycorrhizal and NM Albizia and Gliricidia. These latter plants avoided drought by maintaining higher xylem pressure potentials and leaf relative water content (RWC). All the four leguminous plants were mycorrhizal dependent. The higher the mycorrhizal dependency (MD), the lower the drought tolerance expressed in terms of drought response index (DRI). The DRI may be a useful determinant of MD, as they are inversely related.

A comparison of arbuscular and ectomycorrhizal Eucalyptus coccifera: growth response, phosphorus uptake efficiency and external hyphal production

“…It has been known for some time that Alnus, Populus, Salix, Eucalyptus and some woody legumes can form both AM and ECM associations (Harley & Harley, 1987). Surprisingly, very few studies have made use of these species to compare the effects of the two types of mycorrhizas (Chatarpaul, Chakravarty & Subramaniam, 1989 ;Osonubi et al, 1991). By inoculating one plant species separately with both types of fungi it should be possible to ascertain which type of fungus enhances growth of that host growing in a particular soil type by the greatest degree, and whether greater growth enhancement is due to a greater increase in nutrient uptake or a smaller diversion of C to the fungus.…”

Inoculation of woody legumes with selected arbuscular mycorrhizal fungi and rhizobia to recover desertified Mediterranean ecosystems

“…This soil was steam sterilized. Five-day-old uniform seedlings of each test legume that were obtained from surface-sterilized seeds (3,18) and were germinated on moist filter paper were inoculated with the selected rhizobial strains (Table 1) to form N2-fixing host-symbiont systems for the different mycorrhizal fungi screened. The corresponding strain of rhizobial inoculum was provided by 1 ml (about 10 cells) of a culture in Allen medium (3) that was applied to the seedling roots.…”

“…Thus, mycorrhizae have been found to increase legume performance (4). Moreover, woody legumes usually exhibit a considerable degree of dependence on mycorrhizae to thrive in stressed situations (9,12,13,18,20,24). Arbuscular mycorrhizae, which are by far the most widespread mycorrhizae in nature, are the most common mycorrhizae in nodulated, N2-fixing legumes (4).…”

Arbuscular mycorrhizal networks: process and functions. A review

“…Even if phosphorus is added to soil in soluble form it soon becomes immobilized as organic phosphorus, calcium phosphates or other fixed forms (Wetterauer and Killon, 1996). AM fungi are known to be effective in increasing nutrient uptake, particularly phosphorus and biomass accumulation of many crops in low phosphorus soil (Osonubi et al, 1991).…”