Biosynthesis and accumulation of compatible solutes such as
proline is a distinctive phenomenon that possibly plays a role in
facilitating the retention of water in the cytoplasm of plants and
maintain leaf RWC under salinity stress 5
. It is understood, but
not yet demonstrated that there might be a relationship between
salt tolerance and the role of proline and other metabolites for
osmotic adjustment in plants. However, some studies suggested
that the amplification in proline concentration may not be
associated with salinity tolerance 16, 17. It has been previously
reported that high proline concentration may also have contributed
in additional regulatory or as an osmoprotective factor in salt stress, such as its role in cell osmotic adjustment in barley roots,
which may control the activity of plasma membrane transporters 18.
Proline biosynthesis is a highly energy-demanding process and
only small amount of that may be required to control plasma
membrane transporters 18. Excessive production of proline may
not be defined by these processes, and it could be a reflection of
poor performance and greater damage in response to salt stress.
Nevertheless our results showed accumulation of proline was
amplified with the increase in salt stress. Furthermore, the elevation
of proline content was followed by a reduction in relative water
content as shown by the negative correlation between the two
parameters