Document Type : Research paper
Authors
1
Department of Horticultural Science Engineering, Faculty of Agriculture and Natural Resources, Imam Khomeini International University, Qazvin, Iran
2
Department of Chemistry, Faculty of Basic Sciences, Azarbaijan Shahid Madani University, Tabriz, Iran
Abstract
This study investigates the effects of arbuscular mycorrhizal fungi (AMF) inoculation (with and without) and paclobutrazol foliar application (0 and 200 μg mL–1) on the physiological and biochemical responses of Dracocephalum moldavica L. under varying water availability (100%, 75%, and 50% of field capacity). Key parameters evaluated include plant growth, pigment content, antioxidant activity, secondary metabolite levels, and stress-related enzyme activities. Water deficit significantly inhibited plant growth and reduced pigment concentrations, while increasing oxidative stress markers such as malondialdehyde (MDA) and electrolyte leakage (EL). In response to drought, plants exhibited elevated phenolic and flavonoid levels, indicating an enhanced defense mechanism. Total phenolic content (TPC) increased with the severity of water stress, peaking at 47.35 GAEs g–1 extract under 75% field capacity (S2), compared to 32.24 GAEs g–1 extract under well-watered conditions (100% field capacity, S0). AMF inoculation notably improved growth, chlorophyll content, phenolic and flavonoid accumulation, and antioxidant enzyme activities, while reducing oxidative stress indicators, highlighting its role in enhancing drought resilience. Mycorrhiza-inoculated plants (M1) exhibited a TPC of 43.00 GAEs g–1 extract, compared to 36.01 GAEs g–1 in non-inoculated plants (M0). Paclobutrazol application promoted a compact growth habit with increased branching, higher chlorophyll content, and enhanced antioxidant capacity. When combined, AMF inoculation and paclobutrazol demonstrated synergistic effects, improving plant tolerance to water stress by stabilizing growth, maintaining pigment levels, and boosting antioxidant defenses. The highest TPC (51.40 GAEs g–1 extract) was recorded under 75% field capacity with AMF inoculation (S1M1), indicating a strong interactive effect. These findings suggest that the integrated use of AMF and paclobutrazol offers a promising strategy to mitigate the adverse effects of water deficiency, promoting healthier and more resilient plant growth. Future research should focus on elucidating the underlying molecular mechanisms to further optimize stress management strategies in crops.
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