Drought Stress Alleviation in Chenopodium quinoa through Synergistic Effect of Silicon and Molybdenum via Triggering of SNF1-Associated Protein Kinase 2 Signaling Mechanism

Abstract

Drought stress negatively impacts agricultural crop yields. By using mineral fertilizers and chemical regulators to encourage plant development and growth, its impact can be mitigated. The current study revealed that exogenous silicon (Si) (potassium silicate; K 2 Si 2 O 5 at 1000 ppm) and molybdenum (Mo) (ammonium molybdate; (NH 4 ) 6 Mo 7 O 2 4 center dot 4H 2 O at 100 ppm) improved drought tolerance in quinoa ( Chenopodium quinoa Willd). The research was conducted in a randomized complete block design with three biological replicates. The treatments comprised T0 (control, water spray), T4 (drought stress), and T1, T2, T3, T5, T6, and T7, i.e., foliar applications of silicon and molybdenum solutions individually and in combination. Results revealed that drought stress predominantly affected the quinoa yield by decreasing the growth, physiological, biochemical, metabolic, hormonal, antioxidant, and ionic attributes. On the contrary, the supplementation of Si and Mo enhanced the growth attributes (shoot, panicle, and root length, No. of leaves per plant, shoot and panicle fresh/dry weight, root fresh/dry weight, No. of seeds and seeds fresh weight per plant), physiological traits (relative water content, chlorophyll, and carotenoids content), biochemical characteristics (total soluble sugars, protein and lipid content), metabolic attributes (total phenolic, fl avonoids, tannins, lycopene, carotene), hormonal contents (indoleacetic acid (IAA), gibberellic acid (GA), salicylic acid (SA)), enzymatic and non-enzymatic antioxidants (catalase, peroxidase and ascorbic acid), and ionic content (potassium (K), (calcium) Ca, (magnesium) Mg, Si and Mo). Under drought stress, Si and Mo reduced electrolyte leakage, abscisic acid (ABA) content, H 2 O 2 production, and sodium uptake. In addition, combined Si and Mo supplementation elevated the expression of the sucrose non-fermenting 1 (SNF1 )-associated protein kinase 2 ( SnRK2 ) ( CqSNRK2.10 ) gene in quinoa under drought stress vs . control, signifying an essential regulatory function for Si and Mo-induced drought stress tolerance. These results imply that the exogenous administration of Si and Mo in combination might be an ef fi cient method to alleviate drought stress on quinoa.