Recent Advances and Future Prospects on Practical Use of Salicylic Acid - Salicylic Acid: Plant Growth and Development - page 367

and recover from disease. The MeSA also may be a mechanism whereby a stressed
plant communicates to neighboring plants, warning them of the threat. Researchers
have demonstrated that a plant may build up its defenses if it is linked in some way
to another plant that is emitting the chemical. The NCAR team has demonstrated
that MeSA can build up in the atmosphere above a stressed forest. Scientists are,
therefore, speculating that plants may use the chemical to activate an ecosystem-
wide immune response. The discovery raises the possibility that farmers, forest
managers, and others may eventually be able to start monitoring plants for early
signs of a disease, an insect infestation, or other types of stress. The discovery also
can help scientists resolve a central mystery about VOCs. For years, atmospheric
chemists have speculated that there are more VOCs in the atmosphere than they
have been able to find. Now it appears that some fraction of the missing VOCs
may be MeSA and other plant hormones. This finding can help scientists better
track the impact of VOCs on the behavior of clouds and the development of
ground-level ozone, an important pollutant (Karl et al. 2008 ).
Hence, it may be resolved from the survey of literature cited above that SA
plays diverse physiological roles in plants and potentially alleviates the devastating
effects generated by biotic and abiotic stresses. In future, the exogenous applica-
tion of this phytohormone might act as a powerful tool in enhancing the growth,
productivity and also in combating the ill effects generated by various abiotic
stresses in plants. The future applications of this plant hormone holds a great
promise as a management tool for providing tolerance to our agricultural crops
against the aforesaid constrains consequently aiding to accelerate potential crop
yield in near future.
7 Conclusion and Perspectives
During the last years, our understanding of the molecular mechanisms of hormone
biosynthesis, perception and response has improved dramatically. Knowledge of
the hormone metabolic and transport pathways will lead to new opportunities to
manipulate hormone levels and thus regulate plant growth. Receptors for many of
the hormone classes have been identified, thus leading to exiting new models for
hormone perception. Detailed knowledge of the receptor function may stimulate
the development of new plant growth regulators. A new information on the nature
of chemicals and the signaling pathways that they are involved has been generated.
Earlier, it was thought that calcium, phosphoinositides and ABA were the key
molecules that participated in abitoic stress signaling. Plant hormones like SA, JA,
NO, which were thought to respond to biotic stresses, have now been implicated in
abiotic stresses also. Other molecules like simple sugars and polyamines are also
involved in these signaling pathways. In future more work should be done to find
out their exact role. Cellular perception of NO may occur through its reaction with
biologically active molecules that could function as 'NO-sensors'. But exactly how
NO evolution relates to its bioactivity in plants remains to be established. The