The objective of this study was to determine the effects of
foliar application of polyamines (PAs) on antioxidant defence
and essential oil production of valerian (Valeriana officinalis
L.) grown under different drought stress treatments (100, 70,
50 and 30% available water content). This study was carried
out using pots in greenhouse condition. Drought–stressed
valerian seedlings were sprayed with 1 mM concentration of
each putrescine (Put), spermidine (Spd) and spermine (Spm).
The results showed that drought stress significantly affected
most biochemical characteristics of valerian plants.
Characteristics including leaf relative water content,
chlorophyll a and b contents were decreased, while
carotenoids and electrolyte leakage were increased with the
increase of water stress. In this research, defensive
characteristics comprising proline content, soluble sugars,
catalase, and ascorbate peroxidase were increased followed by
drought stress to ameliorate the adverse effect of it. Results
revealed that foliar application of Spd and Spm provoked the
antioxidant enzymes activity as well as proline accumulation
in valerian which alleviate the membrane damages.
Consequently, Spd and Spm increased photosynthetic
pigments which act as energy supply for plant growth and
production. Here, putrescine had detrimental effects on CAT
activity and Chl a content. Albeit, PAs presented remarkable
effects under moderate drought stress condition but it showed
reverse trends in severe drought stress condition. In terms of
quantity and quality yield, drought stress reduced root growth
but increased the concentration of essential oils. PAs are able
to alleviate water deficit-induced diminish root growth. These
results suggest that in moderate drought stress, growers can
use PAs to increase productivity valerian.