Mycorrhizal trifoliate orange has greater root adaptation of morphology and phytohormones in response to drought stress

Abstract

Plant roots are the first parts of plants to face drought stress (DS), and thus root modification is important for plants to adapt to drought. We hypothesized that the roots of arbuscular mycorrhizal (AM) plants exhibit better adaptation in terms of morphology and phytohormones under DS. Trifoliate orange seedlings inoculated with Diversispora versiformis were subjected to well-watered (WW) and DS conditions for 6 weeks. AM seedlings exhibited better growth performance and significantly greater number of 1st, 2nd, and 3rd order lateral roots, root length, area, average diameter, volume, tips, forks, and crossings than non-AM seedlings under both WW and DS conditions. AM fungal inoculation considerably increased root hair density under both WW and DS and root hair length under DS, while dramatically decreased root hair length under WW but there was no change in root hair diameter. AM plants had greater concentrations of indole-3-acetic acid, methyl jasmonate, nitric oxide, and calmodulin in roots, which were significantly correlated with changes in root morphology. These results support the hypothesis that AM plants show superior adaptation in root morphology under DS that is potentially associated with indole-3-acetic acid, methyl jasmonate, nitric oxide, and calmodulin levels.

Arbuscular Mycorrhizal Fungi Mediate Drought Tolerance and Recovery in Two Contrasting Carob (Ceratonia siliqua L.) Ecotypes by Regulating Stomatal, Water Relations, and (In)Organic Adjustments

“…The phenomenon could be attributed to the unchanged carbon availability from host plants. In contrast, other studies showed a negative effect of prolonged water stress on AM development [15,[40][41][42][43]. A potential explanation to the limited negative responses of AMF to drought can be related to the length of drought, the mycorrhiza inocula/accessions used in our study having "pre-adaption" properties to water shortage, and/or the higher initial carbon investment of plants into the development of mycorrhizal structures.…”

Benefits of Arbuscular Mycorrhizal Fungi Application to Crop Production under Water Scarcity

“…Under drought conditions, AM colonization overexpressed PtYUC3 and PtYUC8 involved in IAA biosynthesis, and downregulated auxin efflux carriers (PtPIN1 and PtPIN3), while up-regulated auxin-species influx carriers (PtABCB19 and PtLAX2) in roots, leading to significantly higher IAA accumulation in mycorrhizal roots versus non-AM roots [97]. Together with higher IAA, colonized trifoliate orange plants showed a significant increase in MeJA, nitric oxide, and calmodulin in roots, supporting greater root adaptation of morphology as a crucial strategy for drought adaptation [93].…”

“…The content of JA and its precursors was higher in leaves of Digitaria eriantha plants infected by Rhizophagus irregularis under water deficit, relative to noninfected plants, which could enhance plant tolerance to the stress [92]. Likewise, mycorrhizal inoculation substantially increased methyl jasmonate (MeJA) in trifoliate orange plants exposed to drought stress [93]. Under water-stress conditions, significantly higher expression levels of JA-biosynthetic gene SlLOXD in roots and leaves of colonized tomato plants were detected, supporting plant response to drought stress by triggering a LOXD-mediated pathway [10,11].…”

Mycorrhiza Fungus <em>Rhizophagus intraradices </em>Mediates Drought Tolerance in <em>Eleusine coracana</em> Seedlings

“…Moreover, due to the presence of extra radical mycelium (ERM) the plant can effectively absorb water from the tightly held soil water around the roots, thus increase the soil-root hydraulic conductance (13). Previous reports have suggested that the AM symbiosis can help plant to achieve drought tolerance due to physical, nutritional, physiological and cellular processes (14).…”