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 122

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50 Control SA (FL) SA

SA (FL) SA

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75

Time, min

Time, h

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0123456
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Fig. 3 The effect of 50 lMSAon(a)H 2 O 2 production and (b) anionic isoperoxidase content,
(c) total peroxidase and (d) PAL activity in 4-day-old wheat seedlings pretreated or not treated
with 5 mg/l fluridone for 24 h. Mean data of three independent replicates and their SEs are
presented

We further carried out the analysis of dynamics of lignin deposition in the
central cylinder of the basal part of the control and treated wheat plants (Table 1 ).
It shows that treatment of seedlings with SA for 24 h contributes to acceleration of
lignification in the cell walls of root xylem vessels as compared to the control:
staining of cell walls with phloroglucinol was clearly revealed in the roots of 5-d-
old seedlings, while in 6-d-old seedlings it was additionally enhanced. At the same
time controlled lignin deposition in the cell walls was discovered later on, starting
from the 6th day (Table 1 ).
Pretreatment of 3-day-old seedlings with fluridone for 24 h inhibited deposition
of lignin in cell wall of roots not only in 5-day-old but also in 6-day-old seedlings
(Table 1 ). Consequently, preventing SA-induced accumulation of endogenous

Table 1 Qualitative assay of specific lignin staining with phloroglucinol in the basal part of
roots of wheat seedlings pre-treated with 50 lM SA during 24 h in the presence or absence of
fluridone (5-day-old) and then 24 h after exposure of seedlings on 4 lM ABA (6-day-old)
Variant 5 days 6 days
Control - +
SA + ++
(FL) SA - -
(FL ? SA) ? ABA ++
'' -'' indicates absence of staining, number of ''+'' reflects the extent of staining intensity