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Abstract
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Salvia officinalis L. (sage) is a valuable medicinal plant with various secondary
metabolites. These compounds are usually inducible by different stress conditions, for
example, water-deficit stress. Therefore, cost-effective and eco-friendly approaches
for alleviating water-deficit stress in medicinal plant crops are in high demand.
Polyamines (PAs), such as putrescine, have a significant effect on improving crop
yield under water-deficit stress conditions. Therefore, a factorial experiment based
on a completely randomized design using two factors and three replications was
conducted. Treatments included irrigation regime (IR) and timing of IR after foliar
application of putrescine (TIRFP) as follows: irrigation after depletion of 20%, 40%,
60%, and 80% available soil water (ASWD). TIRFP was performed at 0, 24, 48, and
72 h. The treatments affected morphological, physiological, molecular, and biochem-
ical attributes. TIRFP of 72 h under IR of 80% ASWD improved the leaf area index,
relative water content, antioxidant enzyme activities, and total radical scavenging
capacity compared with the controlled treatment. The results of real-time quantitative
polymerase chain reaction (qRT-PCR) and gas chromatography/mass spectrometry
(GC/MS) analysis showed the highest level of sabinene synthase (SS) and bornyl
diphosphate synthase (BPPS), the highest contents of 1,8-cineole, β-thujone, and
camphor appeared in plants after 72 h of TIRFP under IR of 80% ASWD. The find-
ings of this study confirm the protective role of putrescine against water stress. In
conclusion, putrescine foliar application allows for balanced water retention. It pre-
serves antioxidant capacity resulting in efficient photosynthesis and the restricted risk
of oxidative damage under water-deficit stress. It improves sage plants’ physiological
attributes and valuable monoterpenes components of essential oil
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