Foliar GR24 and γ-aminobutyric acid modulate redox signaling, root-system architecture, and mineral homeostasis in tellurite-stressed wheat ( Triticum aestivum L.)

Tellurite (TeO₃2−) is a phytotoxic tellurium (Te) species that disrupts cellular redox homeostasis, mineral nutrition, and root development. However, the signaling events underlying tellurite toxicity and its mitigation in cereals remain poorly understood. This study examined whether foliar application of GR24, a synthetic strigolactone analog, and γ-aminobutyric acid (GABA), individually or jointly, modulates early root signaling and downstream physiological acclimation in wheat (Triticum aestivum L.) exposed to tellurite. A 2 × 4 factorial experiment was conducted using two tellurite conditions and four foliar treatments: solvent control, GR24, GABA, and GR24 + GABA, with five replicate pots. Root reactive oxygen species (ROS), nitric oxide (NO), and calcium (Ca2⁺) signals were monitored for 72 h following the first foliar application. Redox homeostasis, plasma-membrane functioning, root-system architecture, rhizosphere properties, elemental composition, mineral/Te selectivity, and subcellular Te partitioning were subsequently assessed. Both signaling compounds alleviated tellurite-induced injury, with their combined application producing the strongest response by improving redox balance, membrane energization, mineral selectivity, root-system development, and root cell-wall Te retention. Relative to tellurite alone, GR24 + GABA restored total root length from 306 to 536 cm plant−1 (a 75.2% increase) and reduced the root-to-shoot Te translocation factor from 0.409 to 0.123 (a 69.9% decrease). These findings suggest that GR24 and GABA interactively improve tellurite tolerance by reshaping early redox-NO-Ca2⁺ signaling, restoring membrane energization, and coordinating selective nutrient acquisition with root-level Te sequestration.