الفهرس 
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Abstract
The aim of this study was to investigate possibility of
overcoming the adverse effects of water deficit stress (60%ETc)
by improving growth, anatomical features, water relations,
physiological attributes and anti-oxidants defense system of sweet
marjoram (Origanum majorana L.) and sweet basil (Ocimum
basilicum L.) plants grown under water stress conditions using
exogenous application with plant growth promoting rhizobacteria
(PGPR) [105cfu seed-1] as seed soaking application or proline
(1mM) as foliar application.
Our results could be summarized as follows:
Expose both sweet marjoram and sweet basil to water
deficit stress (60%ETc) led to a significant decrease in all studied
growth characters (i.e. plant height, number of branches plant-1,
number of leaves plant-1, leaf area, and root fresh and dry mass
plant-1). In contrast, PGPR or proline alleviates the harmful effects
of water deficit stress and significantly increased the above
mentioned characters in both sweet marjoram and basil plants.
Water stress significantly increased essential oil percent
and water use efficiency (WUE) in both sweet marjoram and
sweet basil plants in comparison to non-water stressed plants,
while it significantly decreased oil yield plant-1 and shoot fresh
and dry weight plant-1. Shoot fresh and dry weight plant-1,
essential oil percent and essential oil yield plant-1 were
significantly increased by PGPR or proline treatments.
In both sweet marjoram and sweet basil plants, waterstressed plants without PGPR or proline (60%ETc) showed a
significant reduction in dimensions of stem due to the reduction in
thickness of cortex, thickness of vascular cylinder, pith diameter
and diameter of xylem vessels. Similarly leaves of sweet
marjoram and sweet basil plants exposed to water stress exhibited
a significant reduction in blade, palisade and spongy tissues
thickness as compared to non-water-stressed plants without PGPR
or proline (control). While, PGPR or proline application greatly
improved all anatomical features of stem and leaf in both
water and non–water stressed plants as compared to the control.
Sweet marjoram and sweet basil plants exposed to water
deficit stress exhibited substantial increases of photosynthetic
pigments concentration, proline concentration, total soluble sugars
concentration, electrolyte leakage, activities of peroxidase (POD),
polyphenol oxidase (PPO) and catalase (CAT), while the relative
water content (RWC) significantly decreased. The results showed
that treatment with PGPR or proline enhanced the antioxidant
defense activities in water stressed sweet marjoram and sweet
basil plants, thus alleviating water deficit stress induced oxidative
damage and enhancing drought tolerance and induced positive
changes in structure of leaf and stem tissues. The protective action
of PGPR was more efficient than proline.