Quantification of mycorrhizal water uptake via high-resolution on-line water content sensors

Abstract

The benefits of mycorrhizas for host plants are well known for a large number of species. However, experimental evaluations of the hyphal contribution to the total water uptake and the assessment of the bulk flow velocity in the hyphae are so far contradictory. Barley (Hordeum vulgaris L. Scarlet) with the inoculum Glomus intraradices was grown in a split plant-hyphal chamber with a 5 mm air gap. During the preparation of the chambers with a loamy-silt soil, water content sensors were inserted in each of the plant and the hyphal compartments. These sensors allow nondestructive measurements with high resolution. In total, 8 drying periods with a length of several days were applied with repeated watering following each drying period. A clear decline in water content in the hyphal compartment during each drying period supports the ability of hyphae to transfer water into the plant compartment. The difference between the decline in the hyphal compartment with and without arbuscular mycorrhyzal fungi is significant at the p< 0.000001 level. The direct and indirect hyphal contribution to the total water uptake was estimated to be about 20%. The application of capacitance sensors for water content determination with a special geometry adapted to the plant-hyphal chambers allows the evaluation of the hyphal water flow with high accuracy.

Redistribution of soil water by a saprotrophic fungus enhances carbon mineralization

“…After 72 h, hydraulic redistribution through hyphae had resulted in an average water flux of 67 μL·cm ) (27). In general, passive mass flow is considered as the main mechanism of water transport in fungal hyphae (28), but active transport mechanisms for water might also be involved, such as cytoplasmic streaming (with velocities of 0.03-0.05 cm·min −1 in hyphae) (29), vesicles moved by motor proteins (up to 0.02 cm·min −1 ) (30), and vacuolar pathways (about 0.005 cm·min −1 ) (31).…”

Mycorrhizal Fungi to Alleviate Drought Stress on Plant Growth

“…Difficulties in clearly interpreting the physiological and biochemical outcomes of AM symbiosis under drought conditions are due to the nature of AM symbiosis, because differentiating the effects of roots alone or of AM fungi alone from their combined effects is difficult (Ruth et al 2011). This distinction becomes crucial when investigating the plant-fungus water relations where isolating the direct effect of AM symbiosis and understanding the real contribution of the AM fungi to the water balance of entire plants are also difficult.…”

Arbuscular mycorrhizal symbiosis and methyl jasmonate avoid the inhibition of root hydraulic conductivity caused by drought

“…AM fungi can directly influence host plant water absorption through different mechanisms: Hyphae explore soil pores inaccessible to plants since their diameter is tenfold smaller than that of root hairs (Smith et al 2010); they can facilitate the formation of stable aggregates in the soil thus increasing soil moisture retention properties (Auge et al 2001), and they can transport 375 to 760 nL of water per hour (Faber et al 1991), accounting for up to 20 % of the total water absorbed by plant roots (Ruth et al 2011). On the other hand, root hydraulic conductivity (L), which provides information about the plant's capacity to take up water from the soil (Gallardo et al 1996), usually decreases under drought stress, but this diminution may be partially avoided by AM symbiosis (El-Mesbahi et al 2012;Bárzana et al 2012).…”