Scrutinizing the role of two distinct elicitors modulating light harvesting potential, specific energy fluxes and physiological tolerance in maize plants under sub-optimal environment

Abstract

Elicitors are substances that have potential to modulate stress responses in plants through enhancing the physiological resilience by strengthening photosystem II functionality. In this study, the efficacy of physical (UV-B) and chemical (sodium salicylate) elicitors on the physiological resilience of maize were examined. Seeds were primed with two distinct elicitors (sodium salicylate and UV-B light) and were exposed to sub-optimal growing environment. Priming treatments were administered in three ways: 1) Maize seeds were subjected to two concentration of sodium salicylate @ of 25 (S1) and 150 (S2) parts per million for a duration of 12 h. 2) Seeds were exposed to UV-B for 5 min (U1) and 15 min (U2); or 3) in combination with both elicitors. Eighteen-day-old plants were exposed to low moisture stress (Soil Moisture Content = 38 ± 2 to 42 ± 2 %) for a duration of 9 to 12 days. Applications of either elicitor U1 or in combination of sodium salicylate U1S1 followed by U1S2 ameliorated the negative consequences; lower declines demonstrating −6 to −36 % decrease in growth and −22.7 to −60.5 % decrease in biomass production as compared to unprimed stress plant (negative control). In a sub-optimal environment, elicitors with low doses sustained the quantum yield showing a lesser decline in maximum quantum yield (F_v/F_m - 26.3 % and −33.3 %) and performance index (PI_ABS - 42.9 % and −47.4). Energy loss (heat dissipation) was downregulated whereas the size and number of active reaction center (Fv/Fo) and the efficiencies of light reaction (φPo/(1- φPo) were upregulated, expressing the lower destruction in light harvesting PSII structure and electron flow (ETo/RC) in plants. Interestingly, the elicitors which sustained maize growth expressing higher relative water content (RWC), antioxidant enzymes activities, better osmotic adjustment with lesser production of oxidative stress markers (MDA and H₂O₂). It was concluded that priming with the combination of two distinct elicitors could provide an effective solution to support a resilient crop production strategy under water deficit conditions.