Effect of exogenously-applied abscisic acid, putrescine and hydrogen peroxide on drought tolerance of barley

The objective of this study was to identify the effect of abscisic acid (ABA), putrescine (Put) and hydrogen peroxide (H2O2) foliar pre-treatment on drought tolerance of barley. Despite water limitation, ABA-sprayed plants preserved increased water content, photosynthetic efficiency of PSII (Phi PSII) and CO2 assimilation rate (P-n) compared to untreated stressed plants. The ABA-treated plants presented also the lowest rate of lipid peroxidation (MDA), lowered the rate of PSII primary acceptor reduction (1 - qP) and increased the yield of regulated energy dissipation (NPQ) with higher accumulation of PGRL1 (PROTON GRADIENT REGULATION LIKE1) protein. These plants preserved a similar level of photochemical efficiency and the rate of electron transport of PSII (ETRII) to the well-watered samples. The significantly less pronounced response was observed in Put-sprayed samples under drought. Additionally, the combined effects of drought and H2O2 application increased the 1 - qP and quantum yield of non-regulated energy dissipation in PSII (Phi NO) and reduced the accumulation of Rubisco activase (RCA). In conclusion, ABA foliar application allowed to balance water retention and preserve antioxidant capacity resulting in efficient photosynthesis and the restricted risk of oxidative damage under drought. Neither hydrogen peroxide nor putrescine has been able to ameliorate drought stress as effectively as ABA.

Automated summary

The study demonstrated that foliar application of ABA enhances drought tolerance in barley by maintaining water content and photosynthetic efficiency, while reducing the risk of oxidative damage. In contrast, putrescine and hydrogen peroxide were less effective than ABA in alleviating drought stress.