Endogenous ABA as a Hormonal Intermediate in the Salicylic Acid Induced Protection of Wheat Plants Against Toxic Ions - Salicylic Acid: Plant Growth and Development - page 123

ABA by the pretreatment with fluridone inhibited the increase in H 2 O 2 and anionic
peroxidase level and activation of PAL and peroxidase being the key enzymes in
lignin biosynthesis. As a consequence, lignin deposition in the cell walls of the
root central cylinder was inhibited. Those results convincingly indicate the regu-
latory role of endogenous ABA in acceleration of lignin deposition in the cell
walls of roots of SA-treated seedlings as also evident from the data showing a
complete recovery of this process during the subsequent action of exogenous ABA
for 24 h on seedlings pretreated with fluridone and SA (Table 1 ).
The sum of obtained data indicate the important role of SA-induced synthesis of
ABA in the regulation of SA-induced activation of the key components of lignin
biosynthesis significantly contributing to the strengthening of barrier properties of
root cell walls and pre-adaptation of plants to possible forthcoming action of
environmental stress factors.
3 Endogenous ABA in SA-Induced Activation of Defensive
Reactions in Wheat Seedlings Subjected to the Influence
of Toxic Ions
Frequently changing environment demands plant adaptation to the conditions of
their growth, which implies the development of a complex network of protective
reactions aimed on the struggle for survival under the stressful environment. Based
on this there is the integration of the effective systems of regulation of cell met-
abolic activity for switching genetic programs from norm to stress aimed on
development of an adequate protection at the level of whole organism. Drought,
disturbance of temperature regime and salinity are most important environmental
factors, which are critical for survival of plants and lead to significant losses of
crop yield. Responses to these stresses are known to be interconnected, employing
common signaling pathways, which allow cell adaptation and lead to similar
changes in plants on morphological, physiological, biochemical and molecular/or
genetic levels (Verslues et al. 2006 ; Shinozaki and Yamaguchi-Shinozaki 2007 ;
Potters et al. 2009 ; Arbona et al. 2010 ; Des Marais and Juenger 2010 ). Due to the
increasing anthropogenic pollution of soils increasing attention is paid to the study
of the effects of excess concentrations of heavy metals (HM) on the plants, which
are also manifested in the disturbance of the processes of their growth and
development (Pál et al. 2006 ; DalCorso et al. 2008 ; Yadav 2010 ).
Survival of plants themselves is known to be due to their ability to struggle
against extreme environment, protecting their vital potential. However, realization
of natural protective mechanisms taking place in plants, when conditions become
worse, is well known to be accompanied by a decline in their productivity and
quality. This raises important question about regulation of stress resistance. The
problem of stress-resistance is most important for plant breeding and is under a
steadfast attention of researchers all over the world. This is indeed the case, since
information concerning the chain of reactions taking place in plants in response to