The degradation, DNA fragmentation and ultimately cell death

The production of reactive oxygen species (ROS) is one of the
biochemical changes occurring in plants subjected to various abiotic stresses
Dat et al. 2000. Reactive oxygen species are highly reactive and they are
partially reduced forms of atmospheric oxygen. ROS are typically resulted from
the excitation of O2 to form singlet oxygen (O2), or from
transferring one, two or three electrons to O2 for generation of a
superoxide (O2–), hydrogen peroxide (H2O2)
or a hydroxyl radical (OH-), respectively Shigeoka et al.
2002. ROS are necessary for intracellular signaling Smirnoff 1993, but their
production at high levels can seriously damage plants by increasing lipid
peroxidation, protein degradation, DNA fragmentation and ultimately cell death
Farooq et al. 2009. Water stress causes an imbalance between light trapping
and its utilization, which reduces photosynthetic activity in leaves.
Dissipation of excess light energy in photosynthetic apparatus results in
generation of ROS Lisar et al. 2012. Plants with high antioxidant levels can
better prevent oxidative damage Parida and Das 2005. Antioxidant enzymes such
as superoxide dismutase (SOD), glutathione reductase (GR), catalase (CAT) and
peroxidase (POX) play a key role in scavenging those activated species, the
preservation of membrane integrity, protection of DNA and proteins degradation
Scandalios 1997. Changes of antioxidants reflect the impact of environmental
stresses on plant metabolism.

Seed priming is
a simple technique, which is used to speed up and synchronize seedling
emergence of many horticultural and field crops 7. Early emergence of
seedlings could be resulted in production of vigorous plants. Moreover, enhancing
seedling emergence percentage could help to establish optimum plant population
density under a wide range of environmental conditions 25. Seedling emergence
and establishment could be considerably improved by hydro-priming 22, 23 and
salt priming 21, 22.

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Despite
the popularity of herb cultivation in different parts of Iran, little
information is available about the accumulation of compatible solutes and
antioxidant enzymes activity and their role in borage response to stresses. Also,
changes
in photosynthetic pigments and fluorescence of borage plants in response to
seed priming and water limitation were not documented so far. Thus, these objectives are conclusively
investigated in this research.