Salicylic Acid: An Update on Biosynthesis and Action in Plant Response to Water Deficit and Performance Under Drought - Salicylic Acid: Plant Growth and Development - page 6

not change at this time (Bandurska and Stroi´ski 2005 ). The results of our recent
study revealed that water deficit of the same level but acting longer affected the
increase of SA level both in leaves and roots of barley seedlings. However, an
increase of SA content was first observed in roots (after 3 days) than in leaves
(after 6 days), which indicates the involvement of SA in signal transduction
between roots and leaves (Bandurska and Cie´lak 2012 ). A significant increase of
SA under the conditions of PEG-induced water deficit was also shown in leaves of
soybean. The examined soybean plants had a higher SA level and were more
resistant to water deficit at the reproductive than the vegetative stage (Hamayun
et al. 2010 ).
3.2 Effects of Exogenous Application of SA on Plant
Resistance to Water Deficit
Exogenous application of SA was found to be effective in modeling of plant
metabolic and physiological processes that may enhance resistance to water def-
icit. SA application at various concentrations through roots, seed soaking and
foliar spraying in a concentration-dependent manner alleviated the negative effect
of water deficit on tissue water status, stomatal conductance, chlorophyll content,
membrane properties and plants physiological activities (Horváth et al. 2007 ;
Hayat et al. 2010 ). The application of SA in muskmelon, either through seed
soaking or foliar application, provided protection against drought. Lower con-
centrations within the range of 0.1-0.5 mM were more effective in reducing the
negative effect of drought than higher concentration (1 mM). The mode of
application did not make any significant difference (Korkmaz et al. 2007 ). In
cucumber, the application of SA by seed soaking or foliar spray ameliorated injury
caused by water deficit. SA was more effective when applied by soaking the seeds
and the best results were obtained using 0.5 mM SA solution (Baninasab 2010 ).
However, application of SA (0.7 mM) in rice was more effective in ensuring better
resistance to water deficit when applied by foliar spray than seed treatment (Farooq
et al. 2009 ). Much higher SA concentrations used to the foliage were effective in
protecting amaranth, tomato (3 mM) and Satureja hortensis (1.0-3.0 mM) plants
against water stress (Umebese et al. 2009 ; Yazdanpanah et al. 2011 ). In wheat, a
beneficial effect on improving resistance to water deficit was shown after leaf
spraying with relatively high SA concentrations, i.e. 3.0 and 50 mM (Singh and
Usha 2003 ; Aldesuquy et al. 2012 ). Foliar spraying with much lower SA con-
centration (1 lM) alleviated the damaging effect of long term drought stress in
Ctenathe setosa and maize providing increased resistance to stress (Kadioglu et al.
2011 ; Saruhan et al. 2012 ). Increased resistance to drought in bean was obtained
similarly as in cucumber by soaking seeds in 0.5 mM SA concentration before
sowing (Sadeghipour and Aghaei 2012 ). Seedlings of four chickpea genotypes